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TM 5-805-7

TECHNICAL MANUAL

WELDING

DESIGN, PROCEDURES AND INSPECTION

HEADQUARTERS, DEPARTMENT OF THE ARMY

20 MAY 1985

TM 5-805-7

REPRODUCTION AUTHORIZATION/RESTRICTIONS

This manual has been prepared by or for the Government and is public prop-

erty and not subject to copyright.

Reprints or republications of this manual should include a credit substantially

as follows: “Department of the Army Technical Manual TM 5-805-7, Welding:

Design, Procedures and Inspection. ”

TM 5-805-7

WELDING: DESIGN, PROCEDURES AND INSPECTION

Chapter

INTRODUCTION

Purpose and scope

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Welding applications

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Chapter 2..

DESIGN AND INSPECTION RESPONSIBILITIES

Designer responsibilities

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Contractor responsibilities

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Inspection requirements

Chapter 3. WELDING PROCESSES

General

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Processes

Shielded metal-arc (SMAW)

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Gas metal-arc (GMAW)

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Flux-cored arc welding (FCAW)

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Gas tungsten-arc (GTAW)

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Submerged arc (SAW)

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Exothermic welding

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Arc-stud welding

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Process selection

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Chapter 4. WELDING OF STAINLESS STEEL

General

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Weldability of stainless steels

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Joint design

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..

Methods of welding stainless steels

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Shielded metal-arc (SMAW)

Gas

metal-arc

(GMAW)

Flux-cored arc welding (FCAW)

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Submerged arc (SAW)

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Special considerations in welding stainless

steels

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . .

Chapter 5. WELDING CARBON STEEL AND LOW-ALLOY STEELS

General

Weldability of carbon and low-alloy steels

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . .

Joint design

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Methods

of welding carbon steels and low-alloy steels

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . ..

Shielded metal-arc (SMAW)

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

&metal-arc (GMAW)

Flux-cored arc welding (FCAW)

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Submerged arc (SAW)

Paragraph Page

1-1

1-2

2-1

2-2

2-3

3-1

3-2

3-3

3-4

3-5

3-6

3-7

3-8

3-9

3-10

4-1

4-2

4-3

4-4

4-5

4-6

4-7

4-8

4-9

5-1

5-2

5-3

5-4

5-5

5-6

5-7

5-8

1-1

2-1

2-3

2-5

3-1

3-2

3-12

3-21

3-22

3-23

3-26

3-28

3-30

4-1

4-5

4-6

4-7

5-1

5-3

5-4

5-5

TM 5-805-7

Paragraph Page

Chapter 6.

Chapter 7.

Chapter 8.

Chapter 9.

Appendix A.

Appendix B.

Bibliography

Figure

3-1.

3-2.

3-3.

3-4.

3-5.

3-6.

3-7.

3-8.

3-9.

3-10.

3-11.

3-12.

3-13.

3-14.

3-15.

3-16.

WELDING ALUMINUM ALLOYS

General

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ôñ}H

Weldability of aluminum alloys

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Joint design

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Methods of welding aluminum alloys

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Gas metal-arc (GMAW)

Gas tungsten-arc (GTAW)

WELDING FOR SPECIAL APPLICATIONS

General

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........Ôñ

Reinforcing steel bars

Rail

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ôñ}Hæ¨üw

Steel castings

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 

Dissimilar combinations

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Coated and clad materials

INSPECTION PROCEDURES

General

Qualification of personnel

Inspectors

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ôñ}

Inspection

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ô

Visual inspection

Magnetic particle inspection

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Penetrant inspection

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Radiographic inspection

Ultrasonic inspection

Destructive testing

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Leak testing

SAFETY

General

Hazards

REFERENCES

QUALIFICATION TESTING

LIST OF FIGURES

6-1

6-2

6-3

6-4

6-5

6–6

7-1

7-2

7-3

7-4

7-5

7-6

8-1

8-2

8-3

8-4

8-5

8-6

8-7

8-8

8-9

8–10

8-11

9-1

9-2

Schematic drawing of SMAW equipment.

Schematic drawing of the SMAW process.

Travel speed limits for current levels used for l/8-inch-diameter E601O SMAW electrode.

Travel speed limits for current levels used for l/8-inch-diameter E6011 SMAW electrode.

Travel speed limits for current levels for l/8-inch-diameter E6013 SMAW electrode.

Travel speed limits for current levels used for l/8-inch-diameter E7018 SMAW electrode.

Travel speed limits for current levels used for l/8-inch-diameter E7024 SMAW electrode.

Travel speed limits for current levels used for 5/32-inch-diameter E8018 SMAW electrode.

Travel speed limits for current levels used for l/8-inch-diameter El 1018 SMAW electrode.

Three types of free-flight metal transfer in a welding arc.

The GMAW processes.

Voltage versus current for E70S-2 l/16-inch-diameter electrode and shield gas of argon with 2 percent oxygen

addition.

Voltage versus current for E70S-2 l/16-inch-diameter electrode and carbon dioxide shield gas.

Voltage versus current for E70S-3 l/16-inch-diameter electrode and shield gas of argon with 2 percent oxygen

addition.

Voltage versus current for E70S-3 l/16-inch-diameter electrode and carbon dioxide shield gas.

Voltage versus current for E70S-4 l/16-inch-diameter electrode and carbon dioxide shield gas.

6-1

6-3

6-4

7-1

7-2

7-3

8-1

8-2

8-3

8-6

8-8

8-12

8-19

8-24

9-1

A-1

B-1

BIBLIO-1

Page

3-1

3-2

3-3

3-4

3-5

3-6

3-7

3-8

3-9

3-10

3-11

3-13

3-14

3-15

3-16

3-17

TM 5-805-7

Page

3-17.

3-18.

3-19.

3-20.

3-21.

3-22.

3-23.

3-24.

3-25.

3-26.

3-27.

4-1.

8-1.

8-2.

8-3.

8-4.

8-5.

8-6.

8-7.

8-8.

8-9.

8-10.

8-11.

8-12.

8-13.

8-14.

8-15.

8-16.

8-17.

Table

3-1.

3-2.

4-1.

8-1.

8-2v

8-3.

8-4.

Voltage versus current for E70S-6 1/16-inch-diameter electrode and carbon dioxide shield gas.

Voltage versus current for E110S 1/16-inch-diameter electrode and shield gas of argon with 2 percent oxygen

addition.

The output current wave form of the pulsed-current power supply.

Steps in short-circuiting metal transfer.

Cross sections of flux-cored wires.

The CTAW process.

The SAW process.

Automatic SAW equipment and controls for automatic welding in the flat position.

Thermit welding crucible and mold.

Steps in stud welding operation.

Stud welding equipment.

Schaeffler’s diagram for the microstructure of stainless steel welds.

Gages for measuring fillet weld contour.

Weld nomenclature.

Disruption of magnetic field by weld-metal defect.

Magnetic field created around a weld as current is passed between two test prods.

Major steps of fluorescent penetrant inspection.

Radiographic setup.

Details of penetrameters.

A scan presentation on cathode ray tube.

Straight beam inspection techniques used in scanning a tee weld.

Scanning procedure using angle beam and straight beam on a corner weld.

Several uses of the IIW block.

Scanning procedures for welds not ground flush.

Scanning procedures for welds ground flush.

Tensile test specimens.

Guided bend test jig.

Free bend test.

Transverse fillet-weld shear specimen.

LIST OF TABLES

Established voltage limits.

Summary of welding processes and application.

Austenitic stainless steels most commonly used for cryogenic and vacuum environment equipment.

Uses of various inspection techniques.

Characteristics of radioisotope sources.

Comparison of ultrasonics with other techniques.

Frequency-application chart.

3-18

3-19

3-20

3-21

3-22

3-24

3-25

3-26

3-27

3-28

3-29

4-3

8-3

8-4

8-5

8-7

8-8

8-10

8-11

8-14

8-15

8-16

8-17

8-18

8-20

8-21

8-22

8-23

Page

3-12

3-31

4-8

8-2

8-9

8-13

8-14

TM 5-805-7

CHAPTER 1

INTRODUCTION

1-1. Purpose and scope

This manual contains criteria and basic data for

welded construction design, construction methods,

and inspection procedures for Army construction.

This manual covers only the following welding pro-

cesses and materials commonly used for field con-

struction projects: shielded metal-arc, gas metal-arc,

gas tungsten-arc,flux-cored arc, submerged arc,

exothermic, and arc stud welding processes. Discus-

sions of physics, chemistry, and metallurgy are lim-

ited to areas helpful in selecting welding processes,

materials, and inspection procedures for the applica-

tions listed in paragraph 1-3. For supplemental

information, see the American Welding Society

(AWS) Welding Handbook (available in five sections)

and TM 9-237. Appendix A lists other works, codes,

and specifications which are referenced in this man-

ual; designers should note that there are differences

among the documents’ requirements. Therefore,

when this material is used, the editions which apply

to a given design must be specified.

1-2. Welding applications

This manual discusses the following materials.

a. Steel.

(1) Structural carbon steel welded to structural

carbon steel.

(2) Structural carbon steel welded to high-

strength, low-alloy steel.

(3) High-strength, low-alloy steel welded to

high-strength, low-alloy steel.

(4) Carbon or high-strength, low-alloy steels for

all types of piping systems.

(5) Concrete reinforcing steel.

(6) Rails.

(7) Steel castings, either carbon or high-

strength, low-alloy.

b. Stainless steels.

(1) Cryogenic vessels and piping materials used

for storage and transport of extremely low-tempera-

ture liquids.

(2) Vacuum chambers.

(3) All other uses.

c. Nickel steels and nickel alloys for cryogenic

vessels and piping systems.

d. Aluminum alloys for cryogenic vessels, piping

systems, and other uses.

e. Carbon and high-strength, low-alloy steels

welded to stainless steels. An example of this use is

when steel supports or stiffeners are attached to

stainless steel vessels.

1-1

TM 5-805-7

CHAPTER 2

DESIGN AND INSPECTION RESPONSIBILITIES

2-1. Designer responsibilities

a. The designer must specify the base metal for

the structure, according to design and service

requirements and provide essential metallurgical

and design information in the specifications. Weld-

ing process and filler metals are selected by the

fabricator or, in some cases, specified by the design

office to fit the material requirements; these items

should be included in the specifications and indi-

cated on the drawings. The joint designs must be

shown on the drawings by a standard welding sym-

bol or by detailed drawings of the weld joints.

b. The designer must determine the welding

requirements, and must develop or select the appro-

priate welding sections of the contract for each proj-

ect. These decisions are based on instructions from

the using agency. The designer must develop con-

tract specifications that ensure the contractor knows

the welding quality that must be maintained. The

designer uses the following criteria to determine the

required degree of control over welding quality.

(1) Strict control over welding procedures and

operations is required in five cases (listed in order of

increasing importance):

(a) Distress in one member could cause at

least partial collapse or failure with some hazard to

life and property; application of the design load may

approach 10,000 cycles over many years.

(b) Some of the welds required for structural

integrity are highly stressed; application of the

design load may exceed 10,000 cycles over many

years.

sate for overloads, abuse, mishandling, “acts of

God,” and similar hazards; application of the design

load may be on the order of 100,000 cycles.

(d) Failure of welds or components could be

catastrophic, as in structures such as bridges or high-

-pressure gas piping systems;fatigue of materials

must be carefully considered or application of

design load is on the order of 2 million cycles.

(e) Applications require the highest quality of

material and workmanship throughout, such as for

nuclear, space, and ballistic applications and for sys-

tems subjected to hazardous chemicals, or extreme

pressures or temperatures.

(2) Less control over welding procedures and

operations is needed where:

(a) Stress levels are low.

(b) WeIds are subjected only occasionally to

design loads.

components, and distress in one member will cause

inconvenience rather than collapse or catastrophic

failure.

c. The designer must establish the inspection pro-

cedures needed to determine the weld quality. The

designer must be familiar with the destructive and

nondestructive methods of evaluating weld quality

and must know their capabilities and limitations.

Procedures to qualify inspectors must be specified.

d. The designer must establish the acceptance

requirements for the welded joints, and must iden-

tify the applicable military standards, specifications,

and codes for meeting these requirements. When

standards, codes, and other specifications are cited,

the contract specification must list the paragraphs or

parts of the publications which are applicable or

excluded. The designer must use only the most

recent codes and specifications.

e. The designer must indicate on the plans or

specifications the extent of inspection and testing

required for the various applications and conditions.

Although the inspection and testing needed depend

primarily on the design requirements, the following

general guidelines should be considered.

(1) Apply value engineering — in short, do not

specify unnecessary testing.

(2) Follow design criteria and codes that specify

the extent of inspection and testing required relative

to working stresses, joint efficiencies, or conditions

of use.

(3) Inspect visually in noncritical applications or

conditions; very little other testing should be

required.

(4) Identify the critical joints and welds and

choose those to be tested. The criticality of each

weld should determine the extent of nondestructive

and destructive tests; these tests supplement the

quality control provided by qualified procedures,

qualified welders and operators, and visual inspec-

tion. The weld can be critical because of high

stresses, impact, vibration, temperature, safety,

insurance against operational failure, hard-to-weld

material, or a combination of these factors. In a mul-

tistory office or warehouse building with structural

2-1

TM 5-805-7

steel framing, for example, testing would be done

mainly at the highly stressed joints. In a critical pip-

ing system, however, either all joints would be

nondestructively tested or a uniformly applied ran-

dom test procedure would be used.

(5) Determine the extent of random testing in

piping, tanks, and other elements that have uniform

joints and design levels. This number can be

expressed as a percentage of all welds in the system,

coupled with a finite test increment. However, the

extent of random testing in large steel structures

with a variety of welds and widely varying design

stresses should not be expressed this way. The

designer is responsible for specifying the appropri-

ate tests for critical and noncritical welds. To insure

clarity in bidding and inspection documents, the

location, numbers, and minimum increment lengths

of the random tests should be clearly outlined.

f. The designer must indicate in the specification

what to do when welds fail to meet acceptance

requirements.

g. The designer must design the weld so that the

operator can reach the weld joint easily. If the joint

is located so that the welder cannot observe the

welding operation easily or position the welding gun

or electrode properly, a poor weld may result. In

such cases, it may be hard or impossible to repair

any weld defects.

(1) The dimensions and shape of the joint sur-

faces should allow the weld metal to penetrate the

joint fully. If pieces of different thicknesses are to be

joined, the edge of the thicker piece should be

tapered to the thickness of the thinner piece. The

tapered transitions must conform to the require-

ments of the following publications, as applicable:

AWS D1.1; the American Society of Mechanical

Engineers (ASME) Boiler and Pressure Vessel Code,

Section III or Section VIII; or the American National

Standards Institute (ANSI) Standard B 31.1.

(2) Good joint design practices for vessels are

shown in section VIII of the ASME Boiler and Pres-

sure Vessel Code; for piping in appendix D of ANSI

B31.1; and for structural work in the American Insti-

tute of Stee] Construction’s (AISC) Manual of Steel

Construction and AWS Dl.1.

(3) In some welding operations, some type of

weld joint backing is used to support the molten

weld metal and prevent excessive penetration. Back-

ing strips, when used, must be of material similar to

the base metals which are penetrated by the weld

metal. Nonconsumable” ‘backing rings in piping sys-

tems should not

essary. Instead, be permitted unless absolutely nec-

penetration can be controlled by

altering the joint design (increasing

decreasing the root opening) or by

ble insert rings.

(4) If the joint is welded from

the root face or

using consuma-

both sides, the

reverse side of the root pass (the side opposite that

on which the weld was deposited) should be

chipped, ground, or gouged out to sound metal

before any welding is done from the second side.

This operation will prevent lack of fusion at the root

of the joint. The reverse side of single “V” weld

joints may also be ground out and rewelded to

improve the contour. Complete penetration groove

welds must be welded from both sides unless a

proper backup plate is used.

h. The designer must decide which welds are to

be peened and which are not and indicate them on

the drawings. Peening is the mechanical working of

metals by hammer blows. This technique is useful

for reducing distortion and residual stresses caused

by shrinkage of the weld metal as it cools. However,

the technique can be harmful if extreme care is not

used. Since it can cause cracking, overlapping, or

other defects, peening is not permitted on surface

passes of the weld joints. Intermediate passes may

be peened only with the contracting officer’s per-

mission. Peening of stainless steel welds is not per-

mitted because it causes hardening of the weld

metal. Care should be taken to prevent peening

when slag is removed from the surface pass with

chipping hammers.

i. The designer must determine if the shape of the

weld surface and its height above the base metal

(reinforcement) are important and indicate the

shape on the drawings. An abrupt change in contour

between the weld surface and the base metal may

result in stress concentrations high enough to cause

failure under service loadings. Therefore, the weld

surface should blend smoothly into the surface of

the base metal. If necessary, the edges of the weld

should be ground to achieve a smooth blend of

surfaces.

(1) Undercut at the edge of the weld can be

repaired by grinding if the depth of undercut does

not exceed 1/1 6 inch. If undercut is deeper than

1/16 inch, it should be repaired by adding weld

metal to this area and then grinding the surface to a

smooth, even contour.

(2) Grinding also should be used to remove

overlap at the weld edges and any abrupt ridges or

valleys in the weld surface.

(3) The maximum amount of weld reinforce-

ment should be between 1/32 and 1/8 inch.

2-2

TM 5-805-7

2-2. Contractor responsibilities

a. The contractor must develop a qualified weld-

ing procedure, provide qualified welders and weld-

ing operators, and produce satisfactory weldment.

(1) The construction drawings and specifica-

tions ordinarily indicate the location of the weld

joints and the type of joint required, but the con-

tractor must handle the details of producing the

weld — for example, the equipment used, number

of passes, choice of electrode, and welding process.

Therefore, the contractor must understand the

objective of the plans and, if necessary, seek guid-

ance from the contracting officer and the welding

engineer or metallurgist assigned to the project.

Those concerned should meet to discuss the status of

the welding program as work progresses.

(2) All welding procedures used for any of the

applications covered by this manual and all welders

and welding operators assigned to these construc-

tion operations must be qualified before production

welding is begun. The contractor must conduct all

qualification, testing and maintain records showing

the testing procedures used and the results of these

tests. These records must always be available to the

inspector and the contracting officer or his

representative.

b. The contractor must make sure the welding

equiprnent is serviced and maintained properly to

produce the required current output, voltage con-

trol, and filler wire feed rate for automatic and semi-

automatic processes. Storage and handling of flux

and coated electrodes must also be done properly.

(1) Flux must be kept free of dirt, mill scale, and

other foreign material. Flux fused during previous

welding operations should not be reused. If there is

no moisture in the flux or on the work during weld-

ing, the quality of submerged-arc weld metal is com-

parable to that obtained with low-hydrogen

electrodes. Packaged flux must be stored in a warm,

dry room. Loose flux stored in open containers

should be subject to the same drying conditions as

low-hydrogen electrodes.

(2) Excessive moisture in the electrode coatings

releases hydrogen during welding, and therefore

adversely affects the quality of the weld. Since this

moisture may be absorbed from the atmosphere,

packaged electrodes should be stored in a dry, warm

room, and loose electrodes should be stored in dry-

ing bins or a holding oven kept at the manufacturer’s

recommended temperature.

(a) With low-hydrogen electrodes, the coat-

ings have few hydrogen-producing constituents.

Special care is taken in manufacturing and packaging

these electrodes to maintain a low content of free

and combined moisture. If these electrodes absorb

much moisture from the atmosphere, they no longer

function as low-hydrogen electrodes. The rate of

moisture absorption depends on the coating compo-

sition and the relative humidity.

(b) The electrode manufacturer should be

asked for recommendations about bake time, hold-

ing oven temperature, and maximum allowable

exposure time for the particular electrode type,

quality of weld required, and relative humidity. If

this information is unavailable, a general rule is to

limit atmospheric exposure to 4 hours for electrodes

removed from the bake oven, from holding ovens, or

from hermetically sealed metal containers. In criti-

cal welding applications or when the relative humid-

ity is 75 percent or higher, the exposure time may

have to be reduced to as little as 1/2 hour. Elec-

trodes which have been wet must not be used.

c. The contractor must ensure tack welding and

jigging is done properly. Parts to be welded must be

held in position before, during, and after welding to

keep them correctly aligned and to minimize distor-

tion caused by shrinkage of the weld metal as it

cools. To do this, tack welding is frequently used

either alone or as a supplement to various jigs, fix-

tures, and clamps. Tack welds, which are subject to

cracking if they are too small, can be a source of

defects when subsequent welds are made. There-

fore, tack welds should always be inspected and, if

cracked, ground out before subsequent welding.

Sound tack welds should be ground to a smooth con-

tour that blends evenly into the base metal. This will

ease complete melting of the tack weld into the sub-

sequent weld. Before welding is begun, the pieces

should be aligned so that afterward the abutting

edges of the parts are within the offset tolerances

specified in the contract.

d. The contractor must take precautions against

adverse weather conditions.

(1) Welding should not be done if the surfaces

are wet or covered with snow, ice, or frost. Local

preheating of the joint area can be used to dry the

joint surfaces. If rain or snow is falling, the joint will

have to be sheltered so that the area will stay dry

during welding.

(2) Welding will not be done in windy or drafty

locations unless curtains or protective screens are

used. Most arc welding processes incorporate a

shield of gas or vaporized electrode coating to pro-

tect the arc and molten weld metal from the air. If

the welding is done in a windy or drafty location,

this shield can be blown away, and an unsatisfactory

weld will result.

(3) Welding should not be done if the tempera-

ture at the weld site is below 00 F. If the tempera-

ture is between O and 32°F, the joint area should be

2-3

TM 5-805-7

preheated to 70oF or higher for welding and kept at

this temperature throughout the welding operation.

preheating of structural steel must conform to AWS

D1.1.

e. The contractor must insure proper repair weld-

ing. Defective welds must be repaired by removing

the defects from the weld joint and rewelding the

joints. Defects may be removed mechanically by

grinding, chipping, or machining, or by arc or flame

gouging. A combination of methods is often

required. For example, if the defects are removed

by flame or arc gouging, the cut surface may need to

be cleaned mechanically and smoothed before the

repair weld is made.

(1) Flame- or arc-cut surfaces of stainless steel

and nickel steel have a heavy scale or oxide coating

that must be removed before welding to keep it

from affecting the quality of the repair weld. Also,

heat from the gouging operation can affect strength

by causing metallurgical changes in the weld metal

adjacent to the cut surfaces. Therefore, an addi-

tional 1/8 inch of metal should be mechanically

removed from these cut surfaces.

(2) Defects in aluminum alloys must be removed

only by mechanical means.

(3) Extra care must be used when removing

cracks from welds. Nondestructive inspection may

not indicate the true length of the crack, which may

be too narrow to be detected with the test method

being used. So, one should remove not only the weld

metal in the crack, but also some sound metal at

each end of the crack. The amount removed should

be twice the base metal thickness or 2 inches,

whichever is less at each end of the crack. After the

metal is taken out and before repairs, welds should

be inspected again to insure that the full length of

the crack has been removed.

(4) Repair welding must be done by a qualified

welder using only qualified welding procedures.

The repair work might be easier with a smaller

diameter electrode or filler wire than was used to

make the original weld.

f. On critical welds or when requested by inspec-

tors or the contracting officer, the contractor must

have a welder or welding operator apply a predeter-

mined identification mark to the completed weld

joint. This mark is normally made on the base metal

next to the weld metal. Materials may be marked by

any method acceptable to the inspector as long as it

does not cause notches or sharp discontinuities that

could fail under service loading. The identifying

mark must remain legible until acceptance of the

weld metals or the structure in which the weld is

contained. When requested, the welder should

apply a mark that will remain legible for the life of

the structure.

g. The contractor must set up procedures for

preheating, postheating, and stress relieving. The

conditions to which a weldment will be exposed dur-

ing service operations determine the thermal treat-

ment necessary. For a broad coverage of thermal

treatment, see the AWS Welding Handbook, Volume

1, “Fundamentals of Welding.” Since preheating

and post-weld heat treatment affect the physical

properties of the weld, the procedures must be set

up in detail by the contractor or fabricator and

included in the welding procedure qualification.

(1) Preheating is the application of heat to a

base metal before welding or cutting. Preheating

may be used during welding to help complete the

welded joint. The need for and temperature of

preheating depend on several factors, such as the

chemical analysis of the material, degree of restraint

of the parts being joined, physical properties at ele-

vated temperatures, material thickness, and ambient

temperature.

(a) Preheating may be required or recom-

mended for welding performed under codes or spec-

ifications such as those of AWS, ASME, or the

American Petroleum Institute (API). However,

preheating does not necessarily assure satisfactory

completion of the welded joint, and requirements

must be suited to the individual materials and

applications.

(b) Preheating may vary from a temperature

which is warm to the touch of the hand when weld-

ing outdoors in winter, to as high as 6000 F when

welding highly hardenable steels. When the ambient

temperature is less than 32 “F, local preheat of the

weld joint area to 700 F is recommended.

(2) Post-weld heat treatment (or postheating) is

a general term covering treatments done after weld-

ing to restore the properties of the base metal and to

produce the desired microstructure in the base and

filler metals. Post-weld heat treatment may require

normalizing, full annealing, quenching and temper-

ing, or solution and precipitation treatments.

(3) Stress relief heat treatment is the uniform

heating of a structure (or part of it) to a temperature

below the critical range, but high enough to relieve

most of the residual stresses; this is followed by uni-

form cooling. Stress relieving should not be con-

fused with other post-weld heat treatment

processes, which may or may not prevent the need

for stress relieving, depending on the maximum

temperature attained in the post-weld heat treat-

ment and the rate of cooling from this temperature.

2-4

TM 5-805-7

2-3. Inspection requirements

Inspection is done to meet contract quality specifi-

cations and to maintain quality control on the weld-

ers and welding operators. Effective inspection

requires cooperation between the welder or welding

operator and the inspector. Inspectors should always

encourage the welders and welding operator to

check their own work and to report questionable

welds or welding procedures. There must also be a

mutual understanding between contractor and gov-

ernment supervisory personnel. Inspection costs

money, but good inspection often saves more than it

costs by reducing expensive, time–consuming

rejects or repairs, and by detecting promptly unsat-

isfactory welding procedures or poor workmanship.

Most inspections are to be done by the contractors

(fabricators) since they will gain or lose from the

quality of the product. They can also take immediate

corrective action when defective weldments are

found. When contractors do their own inspections,

the inspection personnel should be organizationally

separate from the production personnel; inspection

personnel should answer not to the project superin-

tendent but to a quality control element of the orga-

nization. Contractors may employ independent

commercial inspection and testing laboratories to

perform these services, especially when the contrac-

tor’s production or quality requirements vary

widely. If the contractor has provided reliable

inspectors, the government can simply spot check to

make sure the inspection methods were adequate.

Government inspection can be done either by gov-

ernment personnel or by an independent commer-

cial inspection or testing laboratory. The choice will

depend on a number of factors, such as availability

of qualified personnel and equipment, length of the

project, cost of inspection, location of the project,

and criticality of inspection or testing requirements.

When qualified government personnel are available,

they should do the inspection and testing. This is

desirable from the standpoints of administrative con-

trol, maintenance of qualified government inspec-

tion personnel, and personal interest in the quality

of the product. When circumstances require work

by a commercial laboratory, these inspectors act as

agents for the government.

a. Contractual relations.

(1) Designers, contractors, inspectors, welders,

and welding operators should cooperate. The qual-

ity of the welding depends largely on the skill of the

contractor’s personnel, the proper choice of materi-

als, and the adequacy of the welding procedure. The

contractor depends on the inspectors for decisions

about whether the completed welds are acceptable.

(2) Inspectors should develop a clear under-

standing of the specified requirements, interpret

contract provisions consistently, and avoid either

favoring the contractor or making unreasonable

demands. In short, they should be absolutely fair to

both the government and the contractor.

(3) Although inspectors usually make the final

decision about the quality of a weld, they should not

take over the role of supervisors for the contractor.

Acceptability of welds should not be left to discre-

tion, but be based on meeting the specified require-

ments. Competent contractor supervision should be

provided to see that the welding procedures are

being followed and that the requests made by the

inspectors are carried out. As much as possible, the

inspector should ask the contractor’s supervisory

personnel to regulate operations, and should not

give orders directly to workmen.

(4) A thorough knowledge of the work is the

best assurance of a satisfactory job and a good work-

ing relationship between the government and the

contractor. The inexperienced inspector may unwit-

tingly penalize both contracting parties by unduly

emphasizing insignificant but costly details of the

work, thus imposing a needless hardship on the con-

tractor with little benefit to the government. At the

same time, the inspector might overlook other oper-

ations that may be vitally important to the job — for

example, overemphasis on the strength of the weld

when appearance is most important, and vice versa.

b. Inspection force. On a large project, govern-

ment inspection of welding operations is assigned to

an inspection section headed by an experienced

supervisor. This differs from an isolated job of weld-

ing where inspection may be the responsibility of

one or two individuals. On a large project where the

inspection of all welding is given to a specialized

team, assignments in the early stages of construction

may be arranged so that inexperienced inspectors

can watch the actions and decisions of experienced

personnel. This procedure will help train a compe-

tent team that will operate efficiently at a later stage

of work. This approach is not possible, however, on

small projects with only one inspector. Only exper-

ienced construction personnel should be assigned in

such cases.

c. Inspector’s duties. The inspector must examine

in detail each phase of the welding operation to

make sure the work is being done right. The inspec-

tor must observe such requirements as procedure

and welder qualifications, joint design and prepara-

tion, alignment, electrode size and type, welding

equipment, and technique. When an assignment is

rotated, a new inspector must learn about the proce-

dures being followed and the status of welding and

2-5

TM 5-805-7

inspection before assuming inspection

responsibility.

d. Supervision. Good supervision of inspectors is

important to satisfactory welding operations on a

large project. Even the most experienced inspector

can do little unless properly instructed in the work

and given the fullest support in dealings with weld-

ing personnel. The supervisor must clarify the

responsibilities of each part of the organization and

outline the limits of each inspector’s authority. The

supervisor should tell the inspector about all deci-

sions on acceptance requirements and other issues.

It is good supervisory practice to circulate memo-

randa outlining all project decisions made by those

in authority and summarizing matters which inspec-

tors can still decide with some flexibility. Before

decisions are made about construction methods, the

opinions of the inspectors assigned to the work

should be considered. Occasional meetings between

inspectors and supervisors to discuss any job

problems, practices, and requirements are helpful

and often necessary.

TM 5-805-7

CHAPTER 3

WELDING PROCESSES

3-1. General

This chapter contains general requirements for

welding processes that may be used for the applica-

tions covered in paragraph 1-2.

3-2. Processes

a. The welding processes covered by this design

manual are as follows:

(1) Shielded metal-arc (SMAW)

(2) Gas metal-arc (GMAW)

(a) Free-flight transfer

(b) Pulsed-current out-of-position welding

(3) Flux-cored arc welding (FCAW)

(4) Gas tungsten-arc (GTAW)

(5) Submerged-arc (SAW)

(6) Exothermic (Thermit)

(7) Arc stud (STUD)

b. Basically, in the electric welding processes, an

arc is produced between an electrode and the work

piece (base metal). The arc is formed by passing a-

current from the electrode to the work piece

through a gap. The current melts the base metal and

the electrode if it is a consumable type, creating a

molten pool. On solidifying, the weld is formed. An

alternate method employs a nonconsumable elec-

trode such as a tungsten rod. In this case, the weld is

formed by melting and solidifying the base metal at

the joint. In some instances, additional metal is

required and is added to the molten pool from a

filler rod.

c. Electrodes which become the deposited weld

metal are available in various diameters and lengths.

In welding, the molten pool must be protected from

the ambient atmosphere to prevent contamination.

There are three ways to do this. Two involve a flux;

in one, the flux is part of the electrode, either as a

coating on the wire or as the core of a hollow wire.

The second method uses a granulated flux that is

applied separately before welding. The third

method involves a gas such as helium, argon, or car-

bon dioxide. In addition to shielding, the flux may

3-1

TM 5-805-7

function as a deoxidizer to purify the deposited

metal or to form slag to protect the weld metal from

oxidation. The flux may contain ionizing elements to

provide smoother operation, alloying elements to

provide higher strength, and iron powder to

increase production rates. The selection of elec-

trodes for a specific job can be based on the follow-

ing eight factors:

(1) Base metal strength properties

(2) Base metal composition

(3) Welding position

(4) Welding current

(5) Joint design and fit-up

(6) Thickness and shape of base metal

(7) Service conditions and/or specifications

(8) Production efficiency and job conditions

The AWS publishes a group of specifications for fil-

ler metals (electrodes) and recommends the welding

process for which they are to be used. In addition,

AWS D1.1 describes the welding procedures to be

used with the various welding processes.

d. Welding material — electrodes, welding wire,

and fluxes — must produce satisfactory welds when

used by a qualified welder or welding operator using

qualified welding procedures. Welding materials

must comply with the applicable requirements of

AWS D1.1, ASME Boiler and Pressure Vessel Code,

Section II, or other requirements in the contract

specifications.

3-3. Shielded metal-arc (SMAW)

This is the most widely used method for general –

welding application; it may also be referred to as

metallic-arc, manual metal-arc, or stick-electrode

welding.

a. Advantages. The SMAW process can be used for

welding most structural and alloy steels. These

include low-carbon or mild steels; low-alloy, heat-

treatable steels; and high-alloy steels such as stain-

less steels. SMAW is used for joining common nickel

alloys and can be used for copper and aluminum

alloys. This welding process can be used in all posi-

tions — flat, vertical, horizontal, or overhead — and

requires only the simplest equipment. Thus, SMAW

lends itself very well to field work (fig 3-l).

b. Disadvantages. SMAW is clearly inferior to

GMAW if one compares the cost of the time and

materials needed to deposit the weld metal. SMAW

deposits the weld more slowly than does GMAW. In

addition, slag removal, unused electrode stubs, and

spatter add a lot to the cost of SMAW; the latter two

items account for about 44 percent of the consumed

electrodes. Another potential cost is the entrapment

of slag in the form of inclusions which may have to

be removed.

c. Process principles. The SMAW process pro-

duces an arc between the base metal and the elec-

trode. The electrode, put in a hand-held clamp, is

3-2

TM 5-805-7

“

3-3

3-4

TM5-805-7

3-5

TM 5-805-7

3-6

-26

TM 5-505-7

3-7

TM 5-805-7

3-8

TM 5-805-7

struck against the base metal and withdrawn to cre-

ate a gap. The molten portion of the electrode fuses

into the molten pool of the base metal, producing

the weld (fig 3-2). Since SMAW is a manual process,

the operator is primarily responsible for quality of

the weld. Most of the melted electrode metal is

transferred to the work piece; the rest is thrown free

of the weld as spatter or is vaporized. Of that

vaporized, some escapes into the surrounding air,

becomes oxidized, and appears as smoke or fumes.

The electrode used for SMAW has a special covering

which serves several purposes. Part of the covering

contains gas-producing compounds that, when

heated, produce a gaseous envelope around the arc

that displaces air and stabilizes the arc. The covering

also protects the molten weld metal from contamina-

tion by air. Without this stabilization, the arc would

be erratic, would often short out, and generally

would be hard to control. Different gas-producing

compounds are used in the coating, depending on

the type of current — alternating (AC) or direct

(DC). The covering also contains slag-forming mate-

rials that mix with the molten weld metal and pick

up impurities from the weld metal. This cleaning

action improves the quality of the weld. Most of the

electrode coating does not become vaporized but

instead is melted by the arc heat and forms a molten

slag cover over the top of the weld bead. This mol-

ten slag cover helps to control the shape of the weld

bead. It also helps to hold the molten weld metal in

place during out-of-position welding (i.e., welding in

the overhead, vertical, or horizontal positions).

Chapters 4 and 5 discuss the numbering system,

color coding, flux composition, and other data con-

cerning welding electrodes. In shielded metal-arc

welding, five distinct forces are responsible for the

transfer of molten filler metal and molten slag to the

base metal.

(1) Gravity. Gravity is the principal force which

accounts for the transfer of filler metal in flat posi-

tion welding. In other positions, the surface tension

is unable to retain much molten metal and slag in the

3-9

crater. Therefore, smaller electrodes must be used

to avoid excessive loss of weld metal and slag.

(2) Gas expansion. Gases are produced by the

burning and volatilization of the electrode coating

and are expanded by the heat of the boiling elec-

trode tip. The coating extending beyond the metal

tip of the electrode controls the direction of the

rapid gas expansion and directs the molten metal

globule into the weld metal pool formed in the base

metal.

(3) Electromagnetic forces. The electrode tip is

an electrical conductor, as is the molten metal glob-

ule at the tip. Therefore, the globule is affected by

magnetic forces acting at 90 degrees to the direction

of the current flow. These forces produce a pinching

effect on the metal globules and speed up the sepa-

ration of the molten metal from the end of the elec-

trode. This is particularly helpful in transferring

metal in horizontal, vertical, and overhead position

welding.

(4) Electrical forces. The force produced by the

voltage across the arc pulls the small, pinched-off

globule of metal, regardless of the position of weld-

ing. This force is especially helpful when one uses

direct-current, straight-polarity, mineral-coated

electrodes, which do not produce large volumes of

gas.

(5) Surface tension. The force which keeps the

filler metal and slag globules in contact with molten

base or weld metal in the crater is known as surface

tension. It helps to retain the molten metal in hori-

zontal, vertical, and overhead welding, and to deter-

mine the shape of weld contours.

d. Equipment, The equipment needed for

shielded metal-arc welding is much less complex

than that needed for other arc welding processes.

Manual welding equipment includes a power source

(transformer, DC generator, AC generator, or DC

rectifier), electrode holder, cables, connectors,

chipping hammer, wire brush, and electrodes.

e. Welding parameters. Welding voltage, current,

and travel speed are very important to the quality of

the deposited SMAW bead. Table 3-1 shows voltage

limits for some SMAW electrodes. The current limits

are shown in the appendix to AWS A5.1. Figures 3-3

through 3-9 show the travel speed limits for the

electrodes listed in table 3-1.

3-10

TM 5-805-7

WIRE DRIVE MAY BE LOCATED

IN WELDING GUN HANDLE

OR AT WIRE REEL

3-11

TM 5-805-7

“Note all electrodes 1/8-inch diameter except E8018, which is

5/32-inch diameter.

3-4. Gas metal-arc (GMAW)

GMAW is a process in which an electric arc is estab-

lished between a solid, consumable, spool-fed elec-

trode and the work piece. The arc, electrode tip,

and molten weld metal are shielded from the atmos-

phere by a gas. This welding process has been com-

monly called metal-inert-gas welding (MIG). There

are two main types of metal transfer: free flight and

short circuiting. Free-flight transfer can be pro-

jected or spray, repelled, and gravitational or globu-

lar. These three forms of free-flight transfer are

basically for flat position welding (fig 3-10). A modi-

fication of free-flight transfer is pulsed current,

which can be used in all welding positions. The

short-circuiting transfer, sometimes called short-arc,

uses a low current and is for welding thin materials

in all positions. All the GMAW processes use basi-

cally the same equipment, as shown in figure 3-11.

AWS D1.1 describes electrodes, shielding gas, and

welding procedures for GMAW using single

electrodes.

a. Free-flight transfer gas metal-arc welding.

(1) Advantages. The major advantage of free-

flight transfer welding is that high-quality welds can

be produced much faster than with SMAW or

GTAW. Since a flux is not used, there is no chance

for the entrapment of slag in the weld metal. The gas

shield protects the arc so that there is very little loss

of alloying elements as the metal transfers across the

arc. Only minor weld spatter is produced, and this is

easily removed. The free-flight process is versatile

and can be successfully used with a wide variety of

metals and alloys: aluminum, copper, magnesium,

nickel, and many of their alloys, as well as iron and

most of its alloys. The process can be operated in

several ways, including semi- and fully automatic.

GMAW is widely used by many industries for weld-

ing a broad variety of materials, parts, and

structures.

(2) Disadvantages. The major disadvantage of

free-flight transfer is that it cannot be used in verti-

cal or overhead welding due to the high heat input

and the fluidity of the weld puddle. In addition, the

3-12

equipment is complex compared with that for the

SMAW process.

(3) Process principles. In free-flight transfer, –

the liquid drops that form at the tip of the consuma-

ble electrode are detached and travel freely across

the space between the electrode and work piece

before plunging into the weld pool (fig 3-l0). When

the transfer is gravitational, the drops are detached

by gravity alone and fall slowly through the arc col-

umn, In the projected type of transfer, other forces

give the drop an initial acceleration and project it

independently of gravity toward the weld pool, Dur-

ing repelled transfer, forces act on the liquid drop

and give it an initial velocity directly away from the

weld pool. The gravitational and projected modes of

free-flight metal transfer may occur in the gas metal-

arc welding of steel, nickel alloys, or aluminum

alloys using a direct-current, electrode-positive

(reverse polarity) arc and properly selected types of

shielding gases. At low currents, wires of these

alloys melt slowly. A large spherical drop forms at

the tip and is detached when the force due to gravity

exceeds that of surface tension. As the current

increases, the electromagnetic force becomes signif-

icant and the total separating force increases. The

rate at which drops are formed and detached also

increases. At a certain current, a change occurs in

the character of the arc and metal transfer. The arc

column, previously bell-shaped or spherical and

having relatively low brightness, becomes narrower

and more conical and has a bright central core. The

droplets that form at the wire tip become elongated

due to magnetic pressure and are detached at a

much higher rate. When carbon dioxide is used as

the shielding gas, the type of metal transfer is much

different. At low and medium reversed-polarity cur-

rents, the drop appears to be repelled from the work

electrode and is eventually detached while moving

away from the work piece and weld pool, This

causes an excessive amount of spatter. At higher cur-

rents, the transfer is less irregular because other

forces, primarily electrical, overcome the repelling

forces. Direct current reversed-polarity is recom-

mended for the GMAW process. Straight polarity

and alternating current can be used, but require pre-

cautions such as a special coating on the electrode

wire or special shield gas mixtures.

(4) Equipment. The equipment needed for

solid-wire, free-flight transfer welding includes a

power supply, a welding gun, a mechanism for feed-

ing the electrode filler wire, and a set of controls (fig

3-11). Two types of power sources are used for free-

flight transfer welding –- constant current or con-

stant voltage. Motor generator or DC rectifier

power sources of either type may be used. Both

TM 5-805-7

3-13

TM 5-805-7

3-14

TM 5-805-7

3-15

3-16

TM 5-805-7

3-17

3-18

manual and automatic welding guns are available.

The manual welding guns have many designs. All the

manual guns have a nozzle for directing the shield-

ing gas around the arc and over the weld puddle.

The filler wire passes through a copper contact tube

in the gun, where it picks up the welding current.

Some manual welding guns contain the wire-driving

mechanism within the gun itself. other guns require

that the wire-feeding mechanism be located at the

spool of wire, which is some distance from the gun.

In this case, the wire is driven through a flexible

conduit to the welding gun. Another manual gun

design combines feed mechanisms within the gun

and at the wire supply itself’. Argon is the shielding

gas used most often. Small amounts of oxygen (2 to 5

percent) frequently are added to the shielding gas

when steel is welded. This stabilizes the arc and

promotes a better wetting action, producing a more

uniform weld bead and reducing undercut. Carbon

dioxide is also used as a shielding gas because it is

cheaper than argon and argon-oxygen mixtures.

Electrodes designed to be used with carbon dioxide

shielding gas require extra deoxidizers in their for-

mulation because in the heat of the arc, the carbon

dioxide dissociates to carbon monoxide and oxygen,

which can cause oxidation of the weld metal.

(5) Welding parameters. Figures 3-12 through

3-18 show the relationship between the voltage and

current levels, and the type of transfer across the

arcs.

b. Pulsed-current GMAW process.

(1) Advantages. This process is useful when low

heat input is required — when one is working with

thin materials or doing out-of-position welding, for

example. In the lower heat-input range, pulsed cur-

rent has the advantage of the continous projected

spray-transfer process. High-quality welds can be

produced in mild and low-alloy steels. In the weld-

ing of aluminum, larger diameter wires can be used;

welds with less porosity are produced because there

is less hydrogen and oxygen pickup on the wire

surface.

3-19

TM 5-805-7

(2) Disadvantages. The major disadvantage of

this process is the complex power supply required in

addition to the GMAW wire feeder and welding

torch.

(3) Process principles. Pulsed-current GMAW is

a modification of the process used to obtain spray-

type transfer with average current levels in the glob-

ular-transfer range. This process provides a higher

ratio of heat input to metal deposition rate than the

short-circuiting process. Pulsed-current GMAW

operates at heat inputs between those used for spray

transfer and short-circuiting transfer, with some

overlap in the ranges. In this process, the current is

pulsed back and forth between projected-transfer

and gravitational-transfer ranges by electronically

switching the current level back and forth between

them. Figure 3-19 shows the current output-wave

form and metal-transfer sequence. Pulsed-current

welding is also known by the trade name “pulsed-

arc. ”

(4) Equipment. The power sources for pulsed

current combine a three-phase, full-wave trans-

former-rectifier power supply, and a single-phase,

half-wave pulse unit. These units are connected in

parallel, but are electronically switched in operation

to give the output waveform shown in figure 3-19.

I 2 34

Standard GMAW

in this process.

wire feeder and torches are used

c. Short-circuiting transfer GMAW welding.

(1) Advantages. The short-circuiting process is

widely used for quickly welding thin materials (up to

1/4 inch) in all positions; it causes little distortion

and few metallurgical defects. This process is used

on carbon and low-alloy steels, and less often on

stainless steel and aluminum; it is also used for out-

of-position welding of thicker materials.

(2) Disadvantages. Generally, welds made with

the short-circuiting process are of slightly poorer

quality than those produced by the spray-transfer

method. This may not cause trouble if high-quality

welds are not required.

(3) Process principles. The short-circuiting

transfer variation of the GMAW process is generally

similar to spray-transfer welding. The main differ-

ence is the way the molten metal is transferred from

the end of the electrode wire to the weld puddle. In

spray-transfer welding, droplets are transferred

through the arc. With the short-circuiting process,

metal transfer occurs during repetitive short circuits

caused when the molten metal from the electrode

contacts the weld puddle. The welding current is

well below the transition level required for spray

TM 5-805-7

transfer. As the end of the filler wire melts, it forms

a ball (fig 3-20). This becomes larger until it touches

the weld puddle, extinguishing the arc and creating

a short circuit. The arc length is deliberately kept

short so that the metal ball touches the puddle

before it separates from the end of the filler wire.

When the short circuit occurs, the welding current

increases rapidly, causing the drop of molten metal

to be “pinched” from the end of the filler wire. The

arc is reinitiated and the process repeated. The

short-circuiting action is very rapid; as many as 200

short circuits per second may occur. This process is

also known as “short arc, ” dip-transfer, or fine wire

welding,

(4) Equipment. Short-circuiting transfer weld-

ing uses the same constant voltage equipment as

does spray transfer. The power source must have a

device that inserts a variable but controlled amount

of inductance into the electrical circuit. This induc-

tance controls the rate of current increase when the

short circuit occurs and permits the arc to restart

without weld-metal spatter.

(a) Short-circuiting welding requires a smaller

diameter filler wire (0.030-inch diameter, for exam-

ple) than is generally used for spray-transfer

welding.

(b) The shielding gas used for short-circuiting

welding depends on the metal being welded. Argon,

helium, or mixtures of these are used for welding

aluminum. Carbon dioxide, a mixture of carbon

dioxide and argon, or argon with a small oxygen

addition is used when welding mild or low-alloy

steel. For stainless steel, argon with oxygen or car-

bon dioxide additions is used.

3-5. Flux-cored arc welding (FCAW)

Flux-cored, tubular-electrode welding has evolved

from the GMAW process to improve arc action,

metal transfer, weld-metal properties, and weld

appearance.

a. Advantages. The major advantages of flux-cored

welding are reduced cost and higher deposition

rates than either SMAW or solid wire GMAW. The

cost is less for flux-cored electrodes because the

alloying agents are in the flux, not in the steel filler

wire as they are with solid electrodes. Flex-cored

welding is ideal where bead appearance is important

and no machining of the weld is required. Flex-

cored welding without carbon dioxide shielding can

be used for most mild steel construction applica-

tions, The resulting welds have higher strength but

less ductility than those for which carbon dioxide

shielding is used. There is less porosity and greater

penetration of the weld with carbon dioxide shield-

ing, The flux-cored process has increased tolerances

for scale and dirt; there is less weld spatter than with

solid-wire GMAW.

b. Disadvantages. Most low-alloy or mild-steel

electrodes of the flux-cored type are more sensitive

to changes in welding conditions than are SMAW

electrodes. This sensitivity, called voltage tolerance,

can be decreased if a shielding gas is used, or if the

slag-forming components of the core material are

increased. A constant-potential power source and

constant-speed electrode feeder are needed to main-

tain a constant arc voltage.

c. Process principles. The flux-core welding wire,

or electrode, is a hollow tube filled with a mixture of

deoxidizers, fluxing agents, metal powders, and

ferro alloys, as shown in figure 3-21. The closure

seam, which appears as a fine line, is the only visible

23456

3-21

TM 5-805-7

difference between flux-cored wires and solid cold-

drawn wire. Flux-cored electrode welding can be

done in two ways: carbon dioxide gas can be used

with the flux to provide additional shielding, or the

flux core alone can provide all the shielding gas and

slagging materials. The carbon dioxide gas shield

produces a deeply penetrating arc and usually pro-

vides better weld than is possible without an exter-

nal gas shield.

d. Equipment. The equipment and controls for the

flux-core process are similar to, and sometimes the

same as, those used in the stray-transfer method.

The unit consists of a constant-speed wire-drive sys-

tem, water- or air-cooled welding torch, and a con-

stant-potential DC unit with a 100-percent duty

cycle.

3-6. Gas tungsten-arc (GTAW)

The GTAW process uses a nonconsumable electrode

and an inert shielding gas. This process is also known

as TIG (tungsten inert gas) and by the trade name

“Heliarc.” GTAW is similar to other arc-welding

processes in that the heat is generated by an arc

between a nonconsumable electrode and the work

piece, but the equipment and the electrode type

distinguish GTAW from the other arc welding

processes.

a. Advantages. The GTAW process is the most

popular method for welding aluminum, stainless _

steel, and nickel base alloys. It produces top quality

welds in almost all metals and alloys used in indus-

try. The process provides more precise control of

the weld than any other arc welding method

because the arc heat and filler metal are indepen-

dently controlled, Visibility is excellent because no

smoke or fumes are produced during welding; there

is no slag or splatter that must be cleaned between

passes or on a completed weld, GTAW is usually

considered one of the most versatile processes

because it produces the highest quality welds in any

position or configuration, The final major advantage

is reduced distortion in the weld joint because of the

concentrated heat source. This is one of the best

precautions that can be taken to prevent weld crack-

ing or locked-up stresses.

b. Disadvantages. The GTAW process is expensive

because the arc travel speed and weld metal deposi-

tion rates are lower than with some other methods.

In addition, it is less advantageous to use GTAW on

heavy, thick materials.

c. Process principles. In the GTAW process, the

tungsten alloy electrode is mounted in a special

electrode holder designed to furnish a flow of inert

gas around the electrode and the arc. The arc is

CROSS-SECTIONS

OF FLUX-CORED WIRES

3-22

TM 5-805-7

struck between the base metal and the electrode by

one of two methods. In the first, called a scratch

start, the operator actually touches the work piece

with the tungsten and withdraws slightly. The sec-

ond method uses high-frequency discharge from the

electrode to the work piece to establish the arc. This

is better for welds that have to be very clean; a

scratch start could leave particles of tungsten in the

weld, causing brittle spots. After the arc is started,

the filler metal, if required, is fed into the weld pool

near the arc, as shown in figure 3-22. The molten

weld metal, the adjacent base metal, and the elec-

trodes are protected by a flowing gaseous envelope

of inert gas: generally argon, helium, or a mixture of

the two. Most GTAW is done manually, but for pro-

duction or assembly type welds such as long butt

welds, the system can be entirely automated. AC is

used generally for aluminum and magnesium, while

DC straight polarity is used for all other metals.

d. Equipment. The equipment includes an electri-

cal power source, electrode holder (torch), tungsten

or tungsten alloy electrodes, gas flow regulating

equipment, and usually a remote rheostat for off-on

switching and current control (fig 3-22).

(1) There are AC and DC power units with

built-in high frequency generators designed specifi-

cally for GTAW. These automatically control gas

and water flow when welding begins and ends. How-

ever, power supplies without these controls can also

be used.

(2) If the electrode holder (torch) is water-

cooled, a supply of cooling water is needed. Elec-

trode holders are made so that electrodes and gas

nozzles can be readily changed, either for different

sizes or for replacement.

(3) Mechanized GTAW equipment may include

electronic devices for checking and adjusting the

welding torch level, equipment for work handling,

provisions for initiating the arc and controlling gas

and water flow, and filler metal feed mechanisms.

3-7. Submerged arc (SAW)

In the SAW process, the arc is not visible, but is

submerged under a layer of granulated flux (fig 3-

23). This process can be used with either a single

electrode wire or many. AWS D1.1 describes the

procedure, equipment, electrodes, and flux used

with SAW.

a. Advantages. SAW is an efficient process that

can be used on nearly all ferrous metals. Welds of

very good quality are produced in a wide range of

metals thicker than 1/1 6 inch. Carbon, alloy, or

stainless steels up to l/2-inch thick are welded in

one pass, while thicker materials require more

passes. Weld metal deposition rates, arc travel

speeds, and weld completion rates are better than

those for other processes. There is no visible arc and

no weld spatter, and the deep penetrating effect of

concentrated heat allows narrow welding grooves.

Thus, it takes less filler metal to make a joint with

SAW than with other welding processes, The

unfused flux can be recovered and recycled when

the welding is finished.

b. Disadvantages. The basic limitation of SAW is

that it can only be used in the flat position and for

horizontal fillet welds. Welds can be made in the

horizontal position, but since the granular flux

needed to shield the weld metal must be in place in

front of the electrode, complicated dams and sup-

ports may be required to contain the flux. The

equipment used in this process can be hand-held,

but is usually mechanized, making it heavy and cum-

bersome and thereby limiting its use to fabrication

shops. The fused flux must be removed by chipping

and wire brushing.

c. Process principles. SAW takes place beneath

the flux covering without sparks, spatter, smoke, or

flash. The electrode and weld pool are completely

covered at all times during welding. The flux makes

possible these special operating conditions, which

distinguish SAW from other processes. When cold,

the flux does not conduct electricity; therefore, the

welder must establish a conductive path for starting

the arc. This can be done by scratch starting where

the electrode touches the base plate or by burying

some steel wool in the flux at the starting point. In

the molten state, the flux becomes highly conduc-

tive. Once the arc is started, the heat produced by

the current causes the surrounding flux to become

molten. This forms a conductive path, which is kept

molten by the continued flow of welding current.

The buried part of the flux is melted; the visible part

remains unchanged in both appearance and proper-

ties, and can be reused. All currents and polarities

are used, depending on the desired penetration and

bead shape, Reverse polarity provides the best bead

shape and penetration, while straight polarity gives

higher deposition rates but less penetration. Alter-

nating current provides penetration somewhere

between the two and is preferred for multi-wire

welding. The fused flux is chipped off the weld and

discarded.

(1) The welding electrodes must be positioned

properly. Flux is fed in front of and around the elec-

trode by a hopper. The arc is struck and the elec-

trodes moved along the weld. The operator watches

the ammeter and voltmeter readings to control cur-

rent and voltage adjustments. A variable-speed

motor controls the electrode feed; a power-operated

3-23

TM 5-805-7

3-24

carriage controls the travel rate. Unused flux is fed

back into the hopper.

(2) Moderately thick sections of material (up to

1 inch) with a carbon content up to 0.35 percent can

be welded without precautions such as preheating

and postweld heat treatment. Preheating is gener-

ally needed when the carbon content is over 0.35

percent.

(3) Low-alloy steels maybe welded if the weld

area is preheated to slow the rate of cooling. This

must be done to avoid cracking in the weld and heat-

affected zone.

(4) When certain quenched and tempered struc-

tural steels (ASTM A 514 and A 517) are welded,

the heat input must be closely controlled to make

sure strength and notch toughness are retained in

the heat-affected zone. To keep a high level of

strength and notch toughness, heat must dissipate

rapidly so that desirable microstructure form. Any-

thing that delays cooling, such as preheating or high

welding heat inputs, should be avoided.

d. Equipment. Both semi-automatic and automatic

SAW equipment is available; the type used generally

depends on the work to be done, and on economic

factors. Semi-automatic equipment is better for

repair welding and for welding that cannot be done

automatically because of the geometry of the part.

Figure 3-24 shows the equipment needed for auto-

matic SAW; included are a power source, wire feed-

ing system, flux feeding system, and a welding torch.

(1) The power supply may be DC constant cur-

rent, DC constant voltage, or AC. The power supply

and wire-drive mechanism must be designed to

operate together so that the arc length can be con-

trolled effectively. SAW generally is done at higher

currents (500 to 1000 amperes) than other types of

arc welding, so the power supply must have a high

current rating at high duty cycles.

3-25

TM 5-805-7

(2) The electrodes used with SAW are generally

bare rods or wire in coils. The choice of electrode

depends on the way the alloying elements are intro-

duced into the weld. One method is to use mild-

steel electrodes with fluxes containing the alloy.

Another method often used requires special alloy

steel electrodes and neutral flux, and includes low-

carbon steel, low-carbon alloy steel, special alloy

steels, high-carbon steels, stainless steels, and non-

ferrous alloys.

(3) The fluxes are granulated, fusible mineral

materials of various compositions and particle sizes.

The choice of flux depends on the welding proce-

dure, joint configuration, and composition of the

base metal to be welded. The flux may include

alloying elements.

3-8. Exothermic welding

In exothermic welding, heat is generated by the

chemical reaction between a combination of alumi-

num and iron oxide. This mixture is placed in a hop-

per above a mold which surrounds the joint, and is

then ignited. A chemical reaction occurs, and the

molten metal and slag drop through the hopper.

Since the molten metal is heavier than the slag, it

settles to the bottom of the mold and touches the

3-26

steel joint. The molten metal melts the surface of the

metal and fuses with it, forming the weld. This pro-

cess, commonly referred to as “thermit welding, ” is

used for joining reinforcing rods, rails, large castings

or forgings, and for repairing large structural shapes.

Historically, thermit welding was largely confined to

structures made of iron and steel. But recently, the

substitution of a copper oxide for iron oxide has led

to many applications within the electrical industry

such as joining or repairing electrical connectors,

cables, bus bars, and bus tubes. Thermit welding is

also used for welding pipe. In this application the

thermit does not mix with the pipe metal, but

merely furnishes the heat to melt the pipe ends,

which are then butted together as they melt.

a. Advantages.

(1) The welder needs very little instruction or

experience to produce good welds rapidly.

(2) Large sections may be fusion welded, and

large quantities of filler metal may be deposited

quickly. Thermit welding can be roughly compared

to a foundry casting operation. The one difference is

that the metal being poured is considerably hotter

than when melted in a furnace. The completed weld

left in the mold cools slowly, reducing residual

stress.

TM 5-805-7

b. Disadvantages. Molds are needed to hold the

molten metal around the weld joint. For one-of-a-

kind jobs, such as repairs, the molds must be con-

structed individually, and a suitable wax or plastic

form filler materials must be inserted in the gap to

insure

proper clearance between the parts.

Preformed permanent molds are used for repetitive

jobs — welding rails or reinforcing rods, for

example.

c. Process principles. Thermit welding is based on

the fundamental principle that aluminum is more

chemically active than iron. The welding process

consists of mixing the iron oxide and aluminum, both

in powder form, and placing them in a hopper or

crucible above a mold which surrounds the joint

area. (The joint to be welded must be cleaned, prop-

erly spaced, and preheated. ) An ignition powder,

such as a mixture of barium peroxide and aluminum

powder, is placed on top of the thermit, and a fuse is

inserted into the powder. The reaction starts after

the fuse ignites the mixture; this happens at about

2000 “F. The reaction is nonexplosive and takes

about 30 seconds; once the mixture starts to burn, it

is self-propagating. When the reaction is complete,

the molten metal has reached a temperature of

approximately 4500oF, which is nearly 1600oF

higher than the temperature of ordinary molten

steel. The metal is poured into the mold to form the

weld (fig 3-25). The mold is allowed to remain in

position for several hours to permit solidification

and to anneal the weld. The deposited metal cools

uniformly and is comparatively free from stresses.

The mold is then removed and the gates and risers

are cut away, Excess weld can be ground or

machined. Although the principal application of

thermit welding has been with the aluminum and

iron oxide mixture on steel structures, other metals

or their oxides may be included in the thermit mix-

ture. Chromium, nickel, manganese, tungsten, tita-

nium, molybdenum, and cobalt can be used. These

3-27

TM 5-805-7

elements alloy with iron and are used when higher

strength, ductility, or hardness is required. They

also permit control of the temperature and time of

the reaction. Cast iron can be welded with a special

thermit mixture.

d. Equipment. Thermit welding kits are available.

They consist of a permanent mold, prepackaged

thermit charges, consumable tapping discs, charges

of ignition powder, and fuses. An individually con-

structed mold requires wax or foam filler, sand mold

(a special mixture of silica sand and plastic clay), and

gates, risers, pouring gates, and a slag basin (fig 3-

25).

3-9. Arc-stud welding

Arc-stud welding is an arc welding process in which

an electric arc is struck between a metal stud and

another piece of metal. When the surfaces to be

jointed are properly heated, they are brought

together under pressure. A ceramic ferrule sur-

rounding the stud can provide partial shielding. The

process is generally referred to as “stud welding. ”

AWS D1.1 describes stud welding procedures,

equipment, workmanship, quality control, and

inspection requirements.

a. Advantages. Arc-stud welding has many advan-

tages and uses. With this process, there is no need to

drill or punch holes, nor to fasten an object mechan-

ically to a main structure with bolts, rivets, or

screws. Arc-stud welding is widely accepted by all

the metal-working industries. Since virtually every

phase of the operation is automatic, no previous

welding experience is necessary. Inexperienced

operators can be trained quickly, and once the

equipment is set for a particular job, high-quality

welds are quickly and easily made. The welding gun

b. Trigger is depressed

3-28

TM 5-805-7

CONTROL

3-29

TM 5-805-7

is light and easy to handle, making the equipment

very portable.

b. Disadvantages. Since this is a versatile process,

there are no real disadvantages; however, there are

some limitations on its use. Stud welding is approved

for use on low-pressure heating boilers built under

the ASME Boiler and Pressure Vessel Code for all

applications except stay bolts. This includes cover

plates, clean-out or access doors, and studded open-

ings for boiler-tubing water-heater coils. Stud weld-

ing is approved for use on nonpressure parts on

power boilers and unfired vessels.

c. Process principles. In the arc-stud welding pro-

cess, the flux-coated stud is inserted into a collet or

chuck which is an integral part of the gun. A porce-

lain ferrule surrounds each stud to shield the arc,

hold the molten pool in place, and help form an

acceptable fillet shape. The flux on the end of the

stud helps the operator control the arc and make

stud welds in any position. The operator places the

gun in the proper position, and spring pressure from

the gun holds the stud against the work piece. When

the trigger is depressed, it completes an electric cir-

cuit, causing the collet to withdraw the stud from

the work piece a preset distance, creating a gap and

an electric arc. At the end of an automatically timed

interval, the molten end of the stud is plunged into

the molten pool which has formed on the surface of

the plate. The process is similar to conventional

metallic-arc welding because, in effect, the stud

serves as a consumable electrode while the current

is flowing. The molten metal quickly solidifies and

the collet releases the stud (fig 3-26). The operator

removes the gun and is ready for the next welding

operation, all within seconds. Stainless steel, magne-

sium, and aluminum can be welded with basically

the same equipment as that used for steel — except

inert gas must be fed through the gun to protect the

weld.

(2) Low-alloy steels may be satisfactorily stud

welded without preheating if the carbon content is

held to 0.15 percent maximum. To prevent cracking

in the heat-affected zone, preheating is necessary

when the carbon content exceeds 0.15 percent.

(3) The heat-treatable, high-strength, low-alloy

structural steels require more attention since they

usually are hardenable enough to form martensite in

the heat-affected zone. These steels are quite sensi-

tive to underbead cracking, and the weld area is

usually low in ductility. Preheating to about 700°F

is recommended when steels of this category are

stud welded.

d. Equipment. The equipment for stud welding

consists of a DC power source; stud welding gun;

welding cables; ferrules for shielding the arc; and

controls, including timing devices. The equipment is

usually portable, but stationary equipment for large-

scale operations is used widely.

(1) The power source is a normal welding

machine adapted for stud welding. The cables are

made the same way as standard welding cables. The

gun is designed to assure correct alignment and hold

the stud. This gun has a trigger to start current flow

and a timing device that withdraws the stud at the

proper time to create the arc, moves the stud into

the molten pool, and holds it until the molten pool

solidifies (fig 3-27).

(2) A ferrule is used with each stud. It shields ‘--

the arc, protects the welder, and eliminates the need

for a full face helmet. The ferrule concentrates heat

during welding and confines molten metal to the

weld area. It helps prevent both oxidation of the

molten metal during the arcing cycle and charring of

the work piece.

(3) Studs are available in a variety of shapes,

sizes, and diameters. Some are designed for thread-

ing or riveting, others serve as nails. Studs are avail-

able as straight and bent shapes, hooks, or eyebolts.

(1) In practice, the same restrictions apply both

to the metal-arc welding of carbon steels and to stud 3-10. Process selection

welding. Carbon steels with a carbon content up to Table 3-2 is a selection guide for the welding pro-

0.30 percent may be welded without preheating. cesses discussed in this chapter. This table is based

When the carbon content exceeds 0.30 percent, on the particular applications encountered in field

particularly in heavy sections, preheating is advisa- welding.

ble to prevent cracking in the heat-affected zone. In

some cases, a combination of preheating and post-

heating has proven helpful.

3-30

TM 5-805-7

Table 3-2. Summary of welding processes and application

Conditions

Materials

commonly

welded

3-31

TM 5-805-7

CHAPTER 4

WELDING OF STAINLESS STEEL

4-1. General

Stainless steels were originally developed because of

their outstanding resistance to corrosion. They also

exhibit good mechanical properties, which can be as

important to the life of the structure as the corrosion

resistance. There are four types of stainless steel:

martensitic, ferritic, austenitic, and precipitation

hardened. These steels exhibit a wide range of

mechanical properties both at room temperatures

and at cryogenic temperatures (below – 150

degrees F). The stainless steels commonly used are

covered in specifications of ASTM, the American

Iron and Steel Institute (AISI), the Society of Auto-

motive Engineers (SAE), ASME, API, and the mili-

tary or other Federal agencies. Commonly used

stainless steels are the austenitic class that meet

specifications for AISI grades in the 200 and 300

series. Martensitic stainless steels in the AISI 400

series are also used. When designing for 400 series

stainless steels, one must use extra care because of

their sensitivity in heat treating. Stainless steels that

conform to other specifications can be used where

particular requirements must be met. Stainless steel

welding electrodes are specified by AWS or military

documents. Commonly used welding electrodes for

fabrication meet specifications AWS A5.4, A5.9,

A5.11, A5.14, and A5.22.

4-2. Weldability of stainless steels

The austenitic chromium-nickel steels are often

used for cryogenic and vacuum systems. These steels

are characterized by their corrosion resistance, low-

magnetic permeability, good high-temperature

strength, and excellent low-temperature ductility

and notch toughness. Some of the austenitic steels,

however, do have characteristics that restrict their

use in cryogenic applications (table 4-1). But the

austenitic steels are considered the most weldable of

the high alloy steels. Three basic factors affect the

weldability of stainless steels: (1) the chemical com-

position of the base metal and the weld metal, (2)

the microstructure of the base metal and the weld

metal, and (3) the use of the correct welding proce-

dures and techniques

a. Chemical composition. The major constituents

in stainless steels are iron,carbon, manganese,

silicon, chromium, and nickel. The chromium is pri-

marily responsible for the stain and corrosion resis-

tance of these steels. It has an affinity for oxygen and

forms a thin, impervious, protective, oxide layer.

Chromium also has an affinity for carbon and forms

chromium-carbides rapidly between 800 and

1600°F.

(1) When chromium-carbides are formed, they

tie up much of the chromium and severely reduce

the corrosion resistance of the steel. Typically, this

can happen in a zone next to and on either side of

the weld joint. This phenomenon, known as sensiti-

zation, occurs because a region next to the weld is

heated to between 800 and 1600 “F by the welding

arc. If the weld joint is subjected to a corrosive

environment, knife-line attack results. Three tech-

niques are used to mitigate sensitization. These

methods can be expensive and should be used only

when sensitization is a problem.

(a) Extra-low carbon (less than 0.03 percent

carbon) grades of steel can be used. This carbon

content is the maximum amount that is soluble in

stainless steels and does not easily come out of

solution.

(b) Stabilizing elements such as columbium

and tantalum can be used. These form carbides pref-

erentially over chromium, thereby tying up the

carbon.

The most common heat treatment technique is to

solution anneal at 1900°F, then water quench. This

technique puts all the carbon in solution and keeps it

there by rapidly cooling through the 1600 to 800oF

range.

(2) In a fully austenitic stainless steel weld (such

as a type 310), the ductility and soundness of the

weld depend on the carbon to silicon ratio. Ideally,

this ratio should be about 1:2. An increase in silicon

above this ratio causes fissuring (microcracking) in

the weld metal and a rapid loss of ductility. An

increase in the carbon ratio causes a less severe

decrease in ductility without affecting weld sound-

ness. With fully austenitic stainless steels, the car-

bon to silicon ratio must be closely controlled. This

tends to limit the use of such steels when weld joints

with the best quality and ductility are required.

b. Microstructural effects. Two microstructural

factors affect the quality of austenitic stainless steel

4-1

TM 5-805-7

weld joints: ferrite content in weld metal and base

metal, and grain growth in weld metal and the heat-

affected zone. The following discussion describes

methods of controlling these factors. Designers can

use this information to specify the proper base mate-

rials, and welding procedures and materials.

(1) Ferrite content.

(a) Fully austenitic weld joints often tend to

develop microcracks and fissures during welding. To

prevent this, designers should select filler metals or

electrodes that will form an austenitic weld deposit

containing a small percentage of ferrite. Such welds

are highly resistant to cracking. However, if the fer-

rite content becomes too high in cryogenic applica-

tions, the weld metal’s impact strength at service

temperatures can be seriously reduced. For these

applications. the ferrite content of the weld metal

should be within the range of 4 to 10 percent.

(b) The actual ferrite content depends on the

compositions of the base metal and filler metal or

electrode, and the extent to which the weld metal

deposit is diluted by the welded parent metal. A

Schaeffler diagram (fig 4-1) can help designers esti-

mate both the percentage of ferrite in the weld

deposit and the filler metal composition necessary to

form the required ferrite in the weld metal. This

diagram is used to predict the amount of ferrite in

stainless steel weld metal on the basis of weld metal

composition. The diagram shows how the micro-

structure of the weld deposit is affected by the alloy

elements in stainless steel that act like nickel, and

those that act like chromium. The nickel equivalent

group which is the austenite former includes nickel,

carbon, and manganese; an allowance is also made

for the nitrogen content. The chromium equivalent

group which is the ferrite former includes chro-

mium, molybdenum, silicon, and columbium. The

nickel equivalent is the ordinate of the diagram, and

the chromium is the abscissa.

metal, the designer uses the following formulas to

calculate the nickel and chromium equivalents:

nickel equivalent = % nickel + 30 X %

carbon + 0.5 X %

manganese

chromium equivalent = 70 chromium + %

molybdenum + 1.5

X % silicon + 0.5

X % columbium.

The nickel and chromium equivalents are calculated

for both the base and weld metal. The values

obtained are then plotted on the Schaeffler diagram,

and a line is drawn between the two points to indi-

cate the possible ferrite percentages that could be in

the weld metal because of base metal dilution. For

example, if type 302 stainless steel is welded using

type 308 electrode, then the nickel equivalent for

the 302 stainless is 12, and the chromium equivalent

is 18.25. When this point is plotted, it is totally in

the austenitic region, so there will be no ferrite. The

type 308 electrode will have a nickel equivalent of

12, and a chromium equivalent of 21, thus putting it

close to the 10 percent ferrite line.

(d) The Schaeffler diagram can predict not

only the amount of ferrite in the microstructure, but

also the electrode composition that will prevent

excessive ferrite or martensite content in stainless

steel weld metal. In addition, the diagram is helpful

in estimating the trend of the microstructure devel-

oped when dissimilar steels are welded. If pieces of

carbon steel and stainless steel are to be welded

together, the compositions of the two can be marked

on the diagram; the tie line drawn between them

indicates the microstructure that may be

encountered.

(2) Grain growth. The toughness and ductility of

the heat-affected zone and the weld metal may be

reduced somewhat because of grain growth caused

by the welding heat. However, unless extremely

high welding heats are used or very heavy weld

passes are deposited, the problem of decreased

toughness and ductility resulting from grain growth

is not serious. If impact testing of sample weld joints

indicates that the notch toughness of the weld metal

or heat-affected zone has suffered, the welding pro-

cess should be modified to decrease the heat input

to the joint and thus restrict the amount of grain

growth.

c. Preweld and postweld heat treating. Weld

joints in stainless steel are neither preheated nor

postheated. These techniques make the joints cool

slowly and could cause sensitization, with a resulting

loss of notch toughness. However, rapid cooling

after welding prevents sensitization of the weld

metal and heat-affected zone. In multipass welds,

the maximum interpass temperature should be

300 “F. Stress relieving of austenitic stainless steel

weld joints also should be avoided because it seldom

works and sensitization can occur easily.

d. Weld cracking.

(1) Weld cracking in austenitic stainless steels

can be divided into four types: crater cracks, star

cracks, hot cracks or microfissures, and root cracks.

All four types of cracking are believed to be mani-

festations of the same basic kind of cracking —

namely hot cracking, or in its earliest stage, microfis-

suring. Hot cracking presented many difficulties

some years ago, but now it can be prevented in

4-2

TM 5-805-7

weldments. Hot cracks occur intergranularly; appar-

ently, the segregation of low melting constituents in

the grain boundaries induces fissuring susceptibility.

(a) The formation of microfissures seems to

depend on five factors: the microstructure of the

weld metal; the composition of the weld metal, par-

ticularly the level of residual elements; the amount

of stress imposed on the weld as it cools through the

high temperature range; the ductility of the weld

metal at high temperatures; and the presence of

notches that form incipient cracks at the edge of the

weld.

(b) For many years,

it was believed that

microfissures only developed in the as-deposited

weld metal shortly after solidification. However,

more recent work has clearly shown that microfis-

sures can occur in the heat-affected zones of previ-

ously deposited sound weld beads.

(2) The microstructure of the weld metal

strongly affects microfissuring susceptibility. Weld

metal having a wholly austenitic micro-structure is a

lot more sensitive to conditions that promote

microfissuring than weld metal containing some

delta or free ferrite in the austenitic matrix. As dis-

cussed in a above, the chemical composition —— both

alloy content and residual element content —

strongly influences rnicrofissuring susceptibility of

the wholly austenitic stainless steel weld metals.

Microfissuring is reduced by a small increase in car-

bon content, a substantial increase in manganese, or

an increase in the nitrogen content. The residual

elements that influence cracking most often are

boron, phosphorus, sulfur, selenium, silicon, colum-

bium, and tantalum.

(3) In welding austenitic stainless steels, two dif-

ferent practices are now used, depending on the

microstructure expected in the weld metal.

(a) Whenever possible, ferrite-containing aus-

tenitic weld structure is used. The filler metal must

be selected carefully and the welding procedure

planned in detail to secure the small, but important,

amount of delta ferrite. The Schaeffler diagram, dis-

cussed in b above, has been used frequently for

determining whether a specified weld composition

will contain enough ferrite.

(b) When a wholly austenitic weld structure

must be used, welding materials containing the low-

est possible amount of recognized crack promoters

should be selected. In addition, the amount of alloy

elements known to improve crack resistance should

be increased. Even with the best materials and the

most favorable welding procedure, wholly austenitic

deposits are more crack sensitive than the ferrite-

containing types. Therefore, all phases of welding

and inspection need greater care.

(4) Base metal heat-affected zone cracking in

welded austenitic stainless steels can be a problem

in heavier sections (more than 1-inch thick). Such

cracking can have two causes. One is an intergranu-

lar form of hot shortness in a heat-affected zone

during welding. The weld metal cracks because of

grain boundary liquation or embrittlement at or near

welding temperatures. The other cause for cracking

is a complex phenomenon involving strain-induced

precipitation in the heat-affected zone during post-

weld heat treatments or service at high tempera-

tures (above 450oF). A change in mechanical

properties thus results in stress-rupture failure

under certain conditions. In this form of failure, the

key to the problem is the precipitation of colum-

bium carbides in the stressed heat-affected zones. As

little as 0.1 percent columbium as a residual element

can produce strain-induced precipitation and cause

welded heavy sections to fail by cracking during ser-

vice at high temperatures. A titanium-stabilized

stainless steel, such as type 347, can be used to help

keep a nonstabilized stainless steel from cracking.

e. Other weld defects. Defects besides cracking

occur in the weld metal if an incorrect weld process

or technique is used. These defects include porosity,

slag inclusions, incomplete fusion, inadequate joint

penetration, and undercutting.

(1) Porosity is a cavity-type discontinuity

formed by gas entrapped during solidification. The

gases that form porosity are either driven from solu-

tion in the weld metal because of low volubility at

lower temperatures, or are produced by chemical

reactions in the molten weld pool. These gases are

trapped in the weld metal because solidification

occurs before the gases have time to rise to the sur-

face of the pool. Porosity will form less often if very

high currents or long arc lengths are avoided. The

welding contractor must make sure these variables

are taken into account when the procedure is devel-

oped and the welder qualification tests are con-

ducted. This is especially true for the SMAW

process because high currents and long arc lengths

consume large amounts of deoxidants in the elec-

trode covering, leaving little to combine with the

excess gases in the weld pool. Moreover, the type

and distribution of porosity will give some indica-

tions of its cause. The types of porosity arc classified

in the acceptance standards of the various codes

(ASME, API, or AWS, as applicable). Generally, the

types of porosity depend on the distance between

individual pores or groups of pores.

(a) Uniforrnly scattered porosity can be found

in many weldments and is of little concern because

there is usually enough sound metal between the

pores.

4-4

TM 5-805-7

(b) Clustered porosity is often associated with

changes in arc conditions. For instance, areas where

the arc has been started or stopped frequently con-

tain cluster porosity.

pass and is considered a special case of inadequate

joint penetration.

(2) Slag inclusions are oxides or nonmetallic

solids that become trapped in solidifying metal. The

inclusions either can be completely surrounded by

weld metal or can be between the weld metal and

the base plate. In the SMAW process, chemical reac-

tions between the weld metal and the coating mate-

rials produce a nonmetallic slag that has low

volubility in the weld metal and generally will float

to the surface. Sometimes, the slag is forced into the

weld metal by the stirring action of the arc, or flows

ahead of the arc and is covered by the weld metal.

Proper cleaning and preparation of the weld joint or

proper manipulation of the electrode will reduce the

number of slag inclusions. The welding contractor

can make sure these precautions are included when

welding procedures are developed and welder quali-

fication tests are conducted.

(3) Incomplete fusion occurs when two weld

beads, or the base metal and a weld bead, have not

fused together. This is caused by failure to raise the

adjoining material to the fusion temperature or fail-

ure to dissolve any oxides or other foreign material

on the surface to which the new weld bead must

fuse. Incomplete fusion can be prevented by follow-

ing the approved welding procedure, which should

include cleaning of the preceding bead and contigu-

ous base metal in the weld joint. Particular care

should be used in welding stainless steel because the

high temperature increases the amount of chromium

oxide formed and the steel becomes hard to weld

with the increased oxide layer.

(4) Inadequate joint penetration occurs when

the fusion of the weld and the base metal at the root

of the joint is less than specified by design. Poor

penetration affects weld joints that will be stressed

in service; the root forms a notch that acts as a stress

concentrator, which leads to early failure of the

joint. Although a poorly cleaned joint may cause

inadequate penetration, poor heat transfer condi-

tions in the joint are more often at fault. Heat trans-

fer can be increased by using wider angles for V-

grooves or a larger root opening.

(5) Undercutting refers to either a sharp recess

in the side wall of a weld joint or reduced thickness

of the base plate at the toe of the last weld bead on

high voltages, as well as low current and fast travel

speeds, may increase the tendency to undercut. If

undercutting is a sharp recess in the joint side wall,

it should be smoothed out by grinding or chipping

before the next weld bead is placed. AWS specifica-

tions and the ASME Boiler and Pressure Vessel Code

impose limitations on undercutting.

4-3. Joint design

Weld joints are prepared either by plasma-arc cut-

ting or by machining or grinding, depending on the

alloy. Before welding, the joint surfaces must be

cleaned of all foreign material, such as paint, dirt,

scale, or oxides. Cleaning may be done with suitable

solvents (e. g., acetone or alcohol) or light grinding.

Care should be taken to avoid nicking or gouging

the joint surface since such flaws can interfere with

the welding operation.

4-4. Methods of welding stainless steels

Stainless steels are readily weldable in the field by

SMAW, GMAW, FCAW, and SAW processes.

GTAW can be used for field fabrication, but it is a

slow process. SMAW is used most often because the

equipment is portable and easy to use. GMAW,

FCAW, and SAW are being used more often in the

field because they are economical and produce high-

quality welds. Manufacturers’ recommendations for

welding stainless steel should be followed. These

include recommendations on joint designs, preheat

temperatures, any associated post-weld heat treat-

ment, and shielding gas.

4-5. Shielded metal-arc (SMAW)

SMAW has been the preferred method of welding

because of its versatility, simplicity of equipment,

and wide selection of electrodes available — all of

which are important for field welding applications.

AWS A5.4 is the specification for stainless steel

SMAW electrodes.

a. Electrode classification system. The SMAW

electrode classification code contains an E and three

numbers, followed by a dash and either a 15 or 16

(EXXX-15), The E designates that the material is an

electrode, and the three digits indicate composition.

Sometimes there are letters following the three dig-

its; these letters indicate a modification of the stan-

dard composition. The 15 or 16 specify the type of

current with which these electrodes may be used.

Both designations indicate that the electrode is usa-

ble in all positions: flat, horizontal, overhead, and

vertical.

(1) The 15 indicates that the covering of this

electrodes are usable with DC reverse-polarity only.

4-5

TM 5-805-7

(2) The designation 16 indicates electrodes that

have a lime- or titania-type covering with a large

proportion of titanium-bearing minerals. The cover-

ings of these electrodes also contain readily ionizing

elements — such as potassium — to stabilize the arc

for AC welding.

b. Chemical requirements. The SMAW electrode

requirements for the nickel-chromium austenitic

stainless steels are included in AWS A5.4. The

chemical requirements are based on the as-depos-

ited weld metal chemistry. Chemical requirements

do not change when a 15 or 16 electrode is used.

c. Weld metal mechanical properties. The AWS

requires the deposited weld metal to have a mini-

mum tensile strength of 60,000 to 100,000 psi, with

minimum elongations of 20 to 35 percent. The

detailed requirements are in AWS A5.4.

d. Recommended filler metals for austenitic stain-

less steels. The Welding Handbook, section 4, “Met-

als and Their Weldability, ” chapter 64, “The 4-10

Percent Chromium-Molybdenum Steels and the

Straight Chromium Stainless Steels, ” has a table giv-

ing a complete list of base metals by AISI number

and recommended filler metals to join the base met-

als. This table lists not only the chromium stainless

steels, but also heat-resisting stainless steels and all

the austenitic stainless steels. If the type of stainless

steel is not listed, then manufacturers’ recommenda-

tions should be followed. An appendix to AWS A5.4

describes the intended uses of the electrodes.

4-6. Gas metal-arc (GMAW)

GMAW is being used more often for shop and field

Applications because it offers much less downtime

for electrode changes, less loss resulting from stub

ends and spatter, and minimal interpass cleaning

compared to the SMAW process. GMAW can be

done in all positions by using either short-circuiting

transfer or a pulsed voltage power supply. GMAW

has slightly less versatility than SMAW because the

welding gun is bulkier than the electrode holder for

the SMAW; furthermore, the equipment is more

complex and expensive, and requires somewhat

more skill by the operator,

a. Electrode classification system. The classifica-

tion code for GMAW electrode wire consists of an E,

an R, and three digits: ERXXX. The letter E indi-

cates that this is an electrode material, and the R

indicates that it is a welding rod. Since these filler

metals are used for the atomic hydrogen and GTAW

method as well as for SAW and GMAW, both letters

are used. The three-digit number, such as 308 in

ER308, designates the chemical composition of the

filler metal. An “Si” after the classification indicates

that the rod or electrode contains between 0.5 and 1

percent silicon rather than the standard 0.25 to 0.60

percent silicon. An “L” indicates that this electrode

has a carbon content not exceeding 0.03 percent.

The specifications for these electrodes are contained

in AWS A5.9.

b. Chemical requirements. The chemical require-

ments for the GMAW electrodes are in AWS A5.9.

The proportions of elements are similar in elec-

trodes and base metal with the same designation. All

chemical analyses are based on the as-manufactured

electrode wire.

c. Weld metal mechanical properties. The all-weld

metal tensile properties for the chromium-nickel

austenitic stainless steel electrodes are presented in

the appendix of AWS A5.9. These mechanical

properties are the same as those required for the

SMAW electrodes.

d. Shielding gas. Two types of shield gas are used

with the GMAW process: pure argon and argon plus

2 percent oxygen. The minimum thickness which

can be welded using this process is about 1/8 to 3/16

inch.

e. Recommended filler metals for chromium-

nickel stainless steels. The austenitic stainless steels

are listed by AISI specification numbers in the table

“Covered Electrodes Recommended for Welds

Between Stainless and Heat-Resisting Steels” in the

Welding Handbook, section 4, chapter 64. If steels

other than those listed are used, then the manufac-

turer’s recommendation for weld metals and preheat

temperatures should be followed. An appendix to

AWS A5.9 describes the intended uses of the elec-

trode types.

4-7, Flux-cored arc welding (FCAW)

FCAW uses equipment similar to that of GMAW,

and offers the advantages of high deposition and

fluxing ingredients. This process is used primarily in

the flat and horizontal positions, but can be used in

other positions if the proper electrode diameter and

welding currents are selected. Flux-cored, corro-

sion-resisting chromium and chromium-nickel steel

electrodes are specified by AWS A5.22.

a. Electrode classification system. The FCAW

electrodes are classified similarly to the GMAW

electrodes. In the code EXXXT-Y, the EXXX desig-

nation is the same as for the GMAW electrodes and

can be any of the material classification numbers

previously noted. The letter T indicates a continu-

ous tubular electrode with a powdered flux within

the tube. The suffix Y can be any number from 1 to 3

or the letter G. The numbers indicate the external

shielding medium to be used during welding. A “ 1”

4-6

designates an electrode using carbon dioxide shield-

ing gas. A “ 2“ designates an electrode using a mix-

ture of argon plus 2 percent oxygen. A “3”

designates an electrode using no external shielding

gas because the shielding is provided by the core

material. The “G” indicates an electrode with an

unspecified method of shielding; no requirements

are imposed on it.

b. Chemical requirements. A table in AWS A5.22

presents the deposited weld metal’s chemical analy-

sis for austenitic chromium-nickel stainless steel

FCAW electrodes. All classifications of the FCAW

electrodes have chemical requirements except the G

classification, and those requirements are only as

agreed on between the supplier and the purchaser.

c. Weld metal mechanical properties. The

all–weld metal tensile requirements for the austen-

itic chromium-nickel stainless steel FCAW elec-

trodes are presented in a table in AWS A5.22. The

tensile strength minimums vary from 60,000 to

80,000 psi, with a minimum elongation between 20

and 35 percent. The G classification of the elec-

trodes does not have any requirements except those

the supplier and purchaser agree on.

d. Shielding gas. The FCAW electrodes can use

three types of shielding: carbon dioxide, argon plus

2 percent oxygen, or inner shield. The inner shield

method uses gas-producing materials within the core

of the electrode. The shielding gas for the G desig-

nation electrode is not specified.

e. Recommended filler metals for austenitic chro-

mium-nickel stainless steeIs. The recommended fil-

ler metal/base metal combinations for the AISI-

designated stainless steels are in a table in the Weld-

ing Handbook, section 4, chapter 64. If stainless

steels other than those listed are to be used, then

manufacturers’ recommendations for weld metal

should be followed. An appendix to AWS A5.22 for

FCAW electrodes lists the intended uses of the

electrodes.

4-8. Submerged arc (SAW)

The SAW process is limited to flat position and hori-

zontal fillet welds because a granulated flux is used

to protect the arc and the molten weld metal. SAW

electrodes are specified by AWS A5.9. This is the

same specification for the GMAW electrodes. For

SAW, DC reverse polarity or AC may be used. Basic

fluxes are generally recommended to minimize

silicon pickup and the oxidation of chromium and

other elements. In general, electrodes having a

silicon content of 0.6 percent or less are desirable

for submerged arc welding since the fluxes usually

result in some silicon pickup. The material classifica-

tion, chemical requirements, and mechanical prop-

erty requirements are the same as those for the

GMAW electrodes in the as-welded condition. The

recommended filler metals for the austenitic chro-

mium-nickel stainless steel are the same as those for

the GMAW electrode and are listed in the table in

the Welding Handbook, section 4, chapter 64, as

noted in the above discussion of the recommended

filler metals for other processes.

4-9. Special considerations in welding

stainless steels

a. Effects of thermal properties of stainless steel

on welding conditions and distortion. The thermal

properties (coefficients of thermal conductivity and

expansion, and melting point) of stainless steel differ

somewhat from those of carbon steels. The differ-

ences affect the welding operations, and steps must

be taken to compensate for the effects of these ther-

mal properties. These steps are discussed in para-

graph 7-5.

b. Welding characteristics.

(1) Generally, austenitic stainless steel can be

welded with about 20 percent less heat input than

carbon steels. There are several reasons for this.

Stainless steels have a higher electrical resistivity

than do carbon steels. As a result, stainless steels get

hotter than carbon steels when the same welding

current is used. Thus, a given amount of stainless

steel can be melted with less current than the same

amount of carbon steel. In addition, less heat or cur-

rent is needed to melt austenitic stainless steels

because they have lower melting points than carbon

steel. Finally, the heat conductivity y of these stainless

steels is lower than that of other steels. Therefore,

the heat built up in the metal from the welding

operation flows away from the weld at a slower rate.

The result is that during welding, higher tempera-

tures are reached in a shorter time.

(2) When welded, austenitic stainless steels

tend to warp and buckle more than carbon steel.

This is because the coefficient of thermal expansion

of austenitic stainless steel is about 1-1/2 times as

large as that of carbon steel. This problem is further

aggravated by stainless steel’s lower thermal con-

ductivity, which tends to concentrate welding heat

in a smaller area. To keep warping and buckling to a

minimum, jigs and fixtures, carefully selected weld-

ing sequences, and accurate fitup generally have to

be used. Preheating to reduce distortion should be

avoided when welding austenitic stainless steel since

this could lead to sensitization of portions of the

weld joint.

4-7

TM 5-805-7

(3) Special precautions are required if tack of the weld. It should be inspected to ensure that it

welding is used to control distortion and maintain is sound and does not contain tiny cracks or porosity,

joint alignment. If these precautions are not taken, The surface of the tack weld should be ground to a

tack welds can be a source of weldmetal cracking, smooth, concave contour so that it will be com-

porosity, incomplete penetration, or lack of fusion. pletely melted into the final weld.

A tack weld must be of the same quality as the rest

Table 4-1. Austenitic stainless steels most commonly used for cryogenic and uacuurn environmcnt equipment

4--8

CHAPTER 5

WELDING CARBON STEEL AND LOW-ALLOY STEELS

5-1. General

The steels commonly used in constructing buildings,

bridges, and piping systems are covered in specifica-

tions of ASTM, AISI, ASME, SAE, and APL These

specifications often refer to the same types of steels,

although they put different restrictions on the chem-

ical analysis and mechanical properties. Commonly

used materials for welded construction in buildings

and bridges meet specifications ASTM A 36, A 203,

A 242, A 440, A 441, A 514, A 517, A 572, or

A 588; and for piping systems, specifications ASTM

A 53, A 106, A 134, A 139, A 671, A 672 or A 691

or API 5L, 5LX, or 2H. Carbon or low-alloy steels

which conform to any of many other specifications

(including military and Federal) can be used where

particular requirements must be met. Welding elec-

trodes for steel are specified by MIL-E-22200. Com-

monly used welding electrodes for construction

meet specifications AWS A5.1, A5.5, A5.17, A5.18,

and A5.20, and A5.23.

5-2. Weldability of carbon and low-alloy

steels

The AWS defines weldability as “the capacity of a

metal to be welded under the fabrication conditions

imposed into a specific, suitably designed structure

and to perform satisfactorily in the intended ser-

vice” (AWS A3.0, p. 55). Given this definition, it is

clear that many things affect the weldability of a

specific steel, including joint design, welding pro-

cess, base metal chemistry, weld metal chemistry,

mechanical properties, and impact properties. Gen-

erally, steels specified for welded building and

bridge construction and for piping systems are weld-

able, with good mechanical properties obtained by

proper attention to welding procedures and elec-

trode selection. AWS D1.1 contains a selection

guide in the Technique section that matches elec-

trode types with various ASTM and API steels. Man-

ufacturers’ recommendations should be followed in

developing welding procedures, including heat

treatment and stress relief for high-strength/low-

alloy steels conforming to ASTM A 514, A 517, or

A 710.

a. Welding procedures The welding procedure to

use is governed by the base plate, the structure

being welded, the position of the weld (i.e., flat,

overhead, horizontal, or vertical), and the chemical

composition of the metal. Carbon levels in the base

metal govern the level of preheat temperature used.

As a rule, the higher the carbon level, the higher the

preheat temperature used. Recommended preheat

practices are given in AWS D1.1. Improper welding

can introduce into the weld joint defects such as

porosity, slag inclusions, incomplete fusion, inade-

quate joint penetration, undercutting, and cracking.

Limitations on these various defects are governed by

AWS D1.1, the ASME Boiler and Pressure Vessel

Code, or MIL-R-11468, where the acceptance level

depends on the application.

b. Cracking. Cracking is one of the flaws that

occurs most often in weldments. Cracks occur when

the temperature of the cooling weld and base plate

is within either of two ranges. One is at or slightly

below the solidification temperature of the weld

metal, and the other is from about 4000 F to ambient

temperature. The high temperature cracking is

called hot tearing and occurs because the metal is

weak and has limited plasticity at this temperature.

Fillet welds, weld craters, and the heat-affected

zone display this type of cracking. Low-temperature

cracking, or cold cracking, occurs in root passes of

butt welds and in the heat-affected zone, and is

invariably associated with the presence of hydrogen

as a dissolved impurity.

(1) Hot tearing. High-temperature cracks are

intercrystalline tears that occur at or near the range

of solidification for the metal. They are attributed to

the presence of low-freezing compounds such as

iron sulfide, or solid impurities that have little or no

tensile strength or plasticity at high temperatures.

These tears are in the metal that is last to freeze in

the weld deposit. Sulfur contributes significantly to

hot tearing, while silicon, phosphorus, carbon, cop-

per, and nickel have a lesser role. Manganese, on the

other hand, has a beneficial effect on hot ductility

because it has a greater affinity to sulfur than iron

does. Manganese sulfides form; these have a higher

melting temperature than steel and produce globu-

lar inclusions rather than the intergranular film that

iron sulfide forms. If the ratio of manganese to sulfur

in steel is 60 or greater, then hot tearing is not likely

to occur. Electrodes recommended by AWS D1.1 or

the ASME Boiler and Pressure Vessel Code, as

5-1

TM 5-805-7

appropriate, will produce a weld deposit with mini-

mum hot cracking tendencies. Preheating, control-

ling interpass temperature, and welding with as little

restraint as possible are other ways to control hot

cracking, particularly in a section thickness greater

than 1/2 inch.

(2) Cold cracking.

(a) Cold cracking occurs in the heat-affected

zone and weld metal. This may be caused by

mechanical effects, alloy content, or hydrogen

pickup from moisture in the electrode flux or on

surfaces of the weld joint. Mechanically, high

shrinkage stresses are induced in the weld metal by

the cooling weld and the restraining action of the

base metal. These stresses act in directions parallel

and perpendicular to the weld and their magnitude

may be great enough to cause cracking.

(b) In any thickness of steel, cold cracking

may also occur ‘in the heat-affected zone because of

alloy content. This is called underbead cracking.

The higher the alloy content, the greater the ten-

dency. Susceptibility to underbead cracking maybe

estimated from a steel’s “carbon equivalent, ” which

is determined from the formula:

As the C.E. increases, so does the susceptibility of

the steel to cold cracking. As a steel’s alloy content,

or C. E., increases, its capability to form a hardened

microstructure such as martensite when cooled rap-

idly also increases. Certain areas of the weld joint,

particularly those next to the base metal heat-

affected zone, may cool rapidly enough to produce a

hardened structure which becomes a “metallurgical

notch. ” This hardened zone may be brittle, with a

characteristic low notch toughness. Increasing the

heat input or the preheat/interpass temperature will

slow the cooling rate. However, high-strength, low-

alloy steels should be preheated carefully so the

steel in the heat-affected zone will not be weakened.

This precaution also applies to the use of interpass

temperature, air-arc gouging, post weld heating, and

heat input during welding. Removal of defects,

when repair is permitted, should be by grinding or

air-arc gouging followed by grinding to limit the

heat input effects of the gouging. Steel manufactur-

ers should be consulted for recommendations about

weld repairs. Few of the steels used in bridge or

building construction and piping systems have

enough alloying elements to create a problem with

hardening in the heat-affected zone. Occasionally,

however, a designer might specify a steel that can

harden quickly enough to require preheating.

Preheat temperatures for many of the steels are

listed in the following documents: structural steels

— AWS D1.1; piping materials — ANSI B31.1; fer-

rous materials — ASME Boiler and Pressure Vessel

Code, section HI, appendix III, “Other Applica-

tions, ” and the text Weldability of Steels, edited by

Stout and Doty (1971).

ing. Three factors act simultaneously in hydrogen-

induced cracking: dissolved hydrogen, tensile

stresses, and a low-ductility microstructure such as

martensite. The source of hydrogen is the shield gas,

flux, or surface contamination. The hydrogen is car-

ried as a diatomic molecule to the arc and is con-

verted to the monatomic or ionized state. The

monatomic hydrogen readily dissolves in the molten

weld metal. The exact mechanism by which hydro-

gen causes cold cracking has not been fully

explained. But many investigators believe that as the

weld metal cools, it becomes supersaturated, and

the hydrogen diffuses to a highly stressed area such

as the heat-affected zone or the atmosphere. Once

in the heat-affected zone, it is theorized that the

hydrogen embrittles the metal. Some low-alloy

steels, such as ASTM A 514 or A 517, will transform

to martensite under rapid cooling conditions, and at

the same time will entrap some or all of the hydro-

gen present. However, hydrogen has low volubility

in the martensitic structure and tends to migrate to

any neighboring discontinuities. Along with external

forces, the hydrogen enlarges these flaws to a criti-

cal size. Regardless of the mechanism by which

hydrogen embrittles the carbon and low-alloy steels,

however, precautions should be taken against its

entrainment. Joint design and attention to joint fit-

up can reduce the chances of cold cracking. To con-

trol hydrogen-induced cracking, a post-weld tem-

perature of 300 to 400 “F for up to 10 hours

(depending on weld thickness) is recommended.

This technique should be specified with caution

because of the risks noted in (3) below. Cleaning

joints to remove hydrogen-containing materials such

as oil and grease, and using of low hydrogen elec-

trodes are also recommended to limit the source of

hydrogen.

(3) Reheat cracking. Reheat cracking occurs in

steels containing carbide-forming alloy elements

such as vanadium or molybdenum. When a post-

weld heat treatment is used, these materials often

exhibit precipitation of alloy carbides that make the

grains of the heat-affected zone stronger than the

grain boundaries. If there are stresses, the grain

5-2

TM 5-805-7

boundary region must adjust to relieve them. Exten-

sive deformation in the grain boundary region may

induce cracking, especially in the heat-affected

zone. The risk of reheat cracking can be reduced by

using electrodes that do not have yield strengths

much higher than that of the base plate, by avoiding

highly rigid joint details in thick plate, by grinding

butt welds flush, and by smoothing the contour of

fillet welds, especially the toe of the weld. The AWS

D1.1 section “Workmanship — Stress Relief Heat

Treatment,” and ASME Boiler and Pressure Vessel

Code, section VIII, “Procedures on Post-Weld Heat

Treatment” contain recommended practices for

heat-treating welds for stress relief. The stress-relief

heat treatment of quenched and tempered ASTM A

514 and A 517 steels is not usually recommended

but may be required to maintain dimensional stabil-

ity during machining.

c. Other defects. Other defects can be introduced

into the weld metal if the proper weld process or

technique is not used. These defects include poros-

ity, slag inclusions, incomplete fusion, inadequate

joint penetration, and undercut. Each of these is

described in paragraph 4-2e.

5-3. Joint design

Weld joints are prepared either by flame cutting or

mechanically by machining or grinding, depending

on the joint details. Before welding, the joint sur-

faces must be cleared of all foreign materials such as

paint, dirt, scale, or rust. Suitable solvents or light

grinding can be used for cleaning. The joint surface

should not be nicked or gouged since they can inter-

fere with the welding operation.

5-4. Methods of welding carbon steels

and low-alloy steels

Carbon and low-alloy steels are readily welded in

the field by SMAW, GMAW, FCAW or SAW.

SMAW is used most often because the equipment is

simple and portable. GMAW, FCAW, and SAW are

being used more often in the field because of weld

quality and economics. Standard joint designs for

these processes are in the AWS D1.1 section

“Design of Welded Connections,” and ASME Boiler

and Pressure Vessel Code, subsection B, “Joint

Details for Pressure Vessels. ” Recommended

preheat temperatures for commonly used steels are

also given in the codes; these figures are based on

plate thickness and the ambient temperature. Rec-

ommended preheat temperatures for

are listed in the AWS D1.1 section,

and appendix R of the ASME Boiler

Vessel Code.

various steels

“Technique,”

and Pressure

5-5. Shielded metal-arc (SMAW)

SMAW has been the preferred method of welding

because of its versatility, the simplicity of its equip-

ment, and the wide selection of electrodes, All of

these characteristics are important for field weld

applications. AWS A5.1 and A5.5 specify mild steel

and low-alloy steel SMAW electrodes.

a. Electrode classification system. The AWS has

developed a classification system which describes

some of the characteristics of steel welding elec-

trodes. The SMAW classification codes are made up

of an E and four and five numbers (EXXYZ). The E

indicates that the material is an electrode. The first

two digits, xX, give the minimum tensile strength of

the weld deposit in 1000 pounds per square inch

(psi); that is, an electrode with an E70YZ classifica-

tion would have a minimum tensile strength of

70,000 psi. The tensile strength designation starts at

60 and increases by 10 to 120. The number repre-

sented by Y can be either 1 or 2 and designates the

proper welding positions for this electrode type. A 1

means that the electrode can be used in all positions:

flat, horizontal, vertical, and overhead; a 2 indicates

that it can be used only on flat or horizontal fillet

welds, The last term in the classification, Z, can be

any number from O through 8. These numbers, iden-

tified in AWS A5.1, indicate major coating constitu-

ents and welding current types.

b. Chemical requirements. The AWS divides

SMAW electrodes into two groups: mild steel (AWS

A5.1) and low-alloy steel (AWS A5.5). The E60XX

and E70XX electrodes are in the mild steel specifi-

cation. The chemical requirements for E70XX elec-

trodes are listed in AWS A5.1 and allow for wide

variations of composition of the deposited weld

metal. There are no specified chemical require-

ments for the E60XX electrodes. The low-alloy

specification contains electrode classifications

E70XX through El 20XX. These codes have a suffix

indicating the chemical requirements of the class of

electrodes — for example, E7010-A1 or E8018-C1.

The composition of low-alloy E70XX electrodes is

controlled much more closely than that of mild steel

E70XX electrodes. Low-alloy electrodes of the low-

hydrogen classification (EXX15, EXX16, EXX18)

require special handling to help the coatings from

picking up water. Manufacturers’ recommendations

about storage and rebaking must be followed for

these electrodes. AWS A5.5 provides a specific list-

ing of chemical requirements.

c. Weld metal mechanical property requirements.

The AWS requires the deposited weld metal to have

minimum tensile and impact strengths. The detailed

requirements for mild steel electrodes are listed in

5-3

TM 5-805-7

AWS A5.1, and for low-alloy steel electrodes in

AWS A5.5.

d. Recommended filler metals for commonly used

steels. Commonly used ASTM and API steels, and

matching filler metal requirements are listed in the

table “Matching Filler Metal Requirements” of AWS

D1.1. This document lists the steel and minimum

preheat and interpass temperatures for different

plate thicknesses and welding processes. If a steel is

not listed, manufacturers’ recommendations should

be followed. AWS A5.1 contains the intended use of

the electrodes as an appendix. Chemical composi-

tion also should be considered when low-alloy elec-

trodes are specified.

5-6. Gas metal-arc (GMAW)

GMAW is being used more often for shop and field

applications because it is more economical than

SMAW. With GMAW, there is much less downtime

for electrode changes, much less loss due to stub

ends and spatter, and much less interpass cleaning

required. GMAW is also slightly less versatile

because the welding gun is bulkier than the elec-

trode holder for SMAW. However, GMAW can be

used in all positions with either short-circuiting

transfer or a pulsed voltage power supply. The

equipment is more complex and more expensive

than that for SMAW, and requires more skill on the

part of the operator.

a. Electrode classification system. The classifica-

tion codes for GMAW electrode wire consist of an E

and four digits in the configuration EXXY-Z. As with

SMAW, the E indicates an electrode, and XX gives

the deposited tensile strength in 10,000-psi incre-

ments. The tensile strength designations range from

70 to 110. The next digit, Y, can be either an S or a

U. The S indicates a solid bare wire, while U means

that the solid wire has an emissive coating that

allows the use of DC straight polarity. The final

digit, Z, can be any number from 1 through 6 or the

letter G. The numbers indicate chemical analysis,

particularly carbon and silicon. The G classification

has no chemical requirements. The letter B at the

end of the code, such as E70S-1B, indicates a low-

alloy steel electrode. Only the E70S-X and E70U-1

electrodes are specified by AWS AS.18.

b. Chemical requirements. The chemical require-

ments for the GMAW electrodes are presented in

AWS AS. 18. The E70S-G and E70S-GB electrodes

have no chemical requirements, except that no addi-

tions of nickel, chromium, molybdenum, or vana-

dium are allowed. Chemical requirements for the

higher-strength low-alloy electrodes are in MIL-E-

18193, MIL-E-19822, MIL-E-23765/1, and MIL-E-

23765/2. All chemical analyses are based on the as-

manufactured electrode wire.

c. Weld metal mechanical properties. The all-weld

metal tensile properties for the E70 electrodes are

presented in AWS A5.18.

d. Shielding gas. Two shield gasses are used with

GMAW—carbon dioxide, and argon plus 1 to 5 per-

cent oxygen addition. Carbon dioxide is used for

short-circuiting transfer and for flat-position weld-

ing. Argon-oxygen shield gas is used with pulsed

voltage out-of-position welding and spray transfer

welding. The GMAW electrodes and recommended

shield gases are listed in AWS A5.18.

e. Recommended filler metals for commonly used

steels. The table “Matching Filler Metal Require-

ments” in AWS D1.1 lists commonly used steels by

ASTM and API specification numbers, and gives

matching filler metal requirements and classifica-

tions. In addition, AWS D1.1 lists the steels and the

minimum preheat and interpass temperatures for

different plate thicknesses and welding processes. If

steels other than those listed are used, manufactur-

ers’ recommendations for weld metals and preheat

temperature should be followed. The intended uses

of the electrode types are indicated in an appendix

to AWS A5.18.

5-7. Flux-cored arc welding (FCAW)

FCAW which uses equipment similar to that of

GMAW, is advantageous because it provides high

deposition and fluxing ingredients. This process is

primarily for flat and horizontal welds, but can be

used in other positions if the proper electrode diam-

eter and welding currents are selected. Mild steel

FCAW electrodes are specified by AWS A5.20.

Low-alloy FCAW electrodes are available; manufac-

turers’ recommendations for their use should be

followed.

a. Electrode classification system. The FCAW

electrodes are classified similarly to the GMAW

electrodes. In the code EXXT-Y, the EXX designa-

tion is the same as for SMAW and GMAW electrodes

and can be either E60T-Y or E70T-Y. The letter T

indicates a continuous tubular electrode with a pow-

dered flux filling the tube. The suffix Y, which can

be any number from 1 through 8 or the letter G,

indicates the deposited weld metal chemistry and

shielding gas used.

b. Chemical requirements. The deposited weld

metal chemical analysis for mild steel FCAW elec-

trodes is in AWS A5.20. There are no chemical

requirements for E70T-2, E70T-3, and E70T-G

electrodes.

c. Weld metal mechanical properties. The all-weld —

metal tensile and impact requirements for the mild

5-4

TM 5-805-7

steel FCAW electrodes are presented in AWS

A5.20.

d. Shielding gas. The FCAW electrodes use car-

bon dioxide for shielding gas or contain in the flux

gas-producing compounds that protect the arc from

atmospheric contamination. The E60T-7, E60T-8,

E70T-4, and E70T-6 electrodes need no external

shield gas. The E70T-1 and E70T-2 electrodes need

additional shielding from carbon dioxide. The E70T-

5 electrode can be used with or without carbon

dioxide as a separate shield gas. The shielding gas

for the E70T-G electrode is not specified.

e. Recommended filler metals for commonly used

steels. Commonly used steels are listed by ASTM

and API specification numbers in the table “Match-

ing Filler Metal Requirements” of AWS D1.1. This

specification also gives the matching filler metal

requirements and the electrode classifications that

meet those requirements. Electrodes E70T-2 and

E70T-3 are not recommended by the AWS Code.

The table “Minimum Preheat and Interpass Temper-

ature” in AWS D1.1 categorizes commonly used

steels, plate thicknesses, and welding processes with

their associated preheat and interpass temperatures.

If steels other than those listed are to be used, manu-

facturer’s recommendations for weld metal and

preheat temperatures should be followed. AWS

A5.20 for FCAW electrodes contains an appendix

that lists the intended use of the electrodes.

5-8. Submerged arc (SAW)

SAW is limited to flat and horizontal fillet welding

because a granulated flux is used to protect the arc

and the molten weld metal. SAW electrodes and flux

for mild steel are specifed by AWS A5.17. Low-alloy

weld metal is specified in AWS A5.23.

a. Material classification. The classification system

for submerged arc electrodes and fluxes has two

parts; the first refers to the flux and the second to

the electrode. Thus, the classification has the follow-

ing: FXX-EXXX. The F indicates that the material is

a flux. The first number indicates the minimum

deposited weld metal tensile strength in l0,000-psi

increments. This digit can be any number from 6 to

12. The last number of this part indicates the impact

requirements of the deposited weld metal. Examples

of flux designations are F61, F86, or F128. The next

part of the classification begins with an E and

designates an electrode. For mild steel, a three- to

five-digit code is used. The first digit, either an L,

M, or H, indicates the relative manganese content of

the electrode wire. The next one or two digits give

the nominal carbon content of the electrode wire.

The code may be followed by a K, which shows the

wire was made from a silicon-killed heat of steel.

Examples of mild steel codes would be EL8K or

EM 12. Low-alloy electrodes have similar coding sys-

tems, with the E again indicating an electrode. The

next two or three digits indicate the as-manufac-

tured wire chemistry. The final part indicates the

deposited weld metal chemistry. This part of the

coding system applies to low-alloy classification

only; the suffix N indicates the material is nuclear

grade. Examples of SAW classifications are F70-

EL12-Al, combination for carbon-molybdenum

low-alloy steels; F86-EB2-B2, combination for chro-

mium-molybdenum low-alloy steels; or F61-

EM12K, combination for mild steel.

b. Chemical requirements. The electrode chemi-

cal composition requirements are presented in AWS

A5.17 for mild steel and AWS A5.23 for low-alloy

steels. The deposited weld metal chemical require-

ments are presented in AWS A5.23 for alloy steels.

The only chemical composition requirement for

fluxes is that the combination of a flux and low-alloy

steel electrode produce a specified deposited weld

metal chemistry.

c. Weld metal mechanical properties. The all-weld

metal tensile and impact requirements for mild and

low-alloy steel welds are presented in AWS A5.17

and A5.23, respectively. The EXXX after the flux

designation means that the flux will produce these

strengths when used in combination with any

electrode.

d. Recommended filler metal for commonly used

steels. The table “Matching Filler Metal Require-

ments” in AWS D1.1 lists the ASTM and API classifi-

cations of commonly used steels, the matching filler

metal requirements, and the electrode classifications

that meet these requirements. The table “Minimum

Preheat and Interpass” in AWS D1.1 lists the steels,

the minimum preheat and interpass temperatures

for a range of plate thicknesses, and the various

welding processes. If steels other than those listed

are to be used, then manufacturer’s recommenda-

tions for weld metals and preheat temperatures

should be followed. The appendices of AWS A5.17

and A5.23 list usages and choice of fluxes for the

SAW process.

5-5

TM 5-805-7

CHAPTER 6

WELDING ALUMINUM ALLOYS

6-1. General

The aluminum alloys commonly used in constructing

pressure vessels, cryogenic vessels, piping systems,

and accessories are specified by the Aluminum Asso-

ciation, Inc. (AA), ASTM, and military or other Fed-

eral specifications.Aluminum welding electrodes

and filler rods are specified in AWS A5.10 or mili-

tary documents.

6-2. Weldability of aluminum alloys

a. Introduction. Most aluminum alloys can be

joined by either GMAW or the GTAW processes.

The weldability of aluminum alloys is essentially the

same for both processes. The most easily welded

alloys are those of the non-heat-treatable lXXX,

3XXX, and 5XXX series, and the heat-treatable

6XXX series; of the 7XXX series, only two alloys

(7005 and 7039) were developed specifically for

welding.

(1) Non-heat-treatable alloys. The composition

of non-heat-treatable aluminum alloys determines

their relative mechanical strength, which increases

with cold work (H temper) or strain hardening.

Alloys in the annealed (O temper) condition have the

weakest mechanical properties. Magnesium-contain-

ing alloys (5XXX) are typically given a low-tempera-

ture stabilization treatment. This lowers the

strength slightly but increases ductility and pro-

duces some precipitation. Reheating or annealing

weakens strain-hardened material.

(2) Heat-treatable alloys. Appropriate solution,

quenching, and precipitation reactions produce

heat-treatable alloys with maximum strength. This

age-hardening mechanism requires an alloying ele-

ment with appreciable solid volubility in aluminum

at elevated temperatures, but with limited solubili-

ties at lower temperatures. Typically, thermal treat-

ments first involve solution heat treatment; that is,

heating to the 900 to 1000oF range but below the

eutectic melting temperature. At these tempera-

tures, the maximum amount of solute is taken into

solution (W temper). By quenching from the solu-

tion treating temperature, a nonequilibrium, super-

saturated solid solution is obtained. Quenching rate

is critical for some alloy compositions, particularly

through the 550 to 750 ‘F range. The degree of

quench sensitivity depends on alloy composition.

Some precipitation from the supersaturated solid

solution at room temperature strengthens the alloy.

However, this natural aging will approach a maxi-

mum strength in time (T4 temper). Of course, the

rate of natural aging and the strengths produced

vary with alloy composition. Holding at reduced

temperatures will slow precipitation of the material

undergoing natural aging. If the material which has

been solution heat treated and quenched is heated

typically to the 300 to 500oF range, desirable pre-

cipitation occurs. This markedly increases the alloy’s

mechanical properties (T6 temper). Heating at

higher temperatures (500 to 800 “F) results in non-

strengthening precipitation of the solute element.

This annealing treatment tends to produce an equi-

librium structure with high ductility and low

strength (O temper).

b. Welding procedures. Welding procedures

should be qualified before work proceeds on the

structure (chapter 2). The welding procedures

depend on the base plate, the structure being

welded, the position of the weld (i.e., flat, overhead,

horizontal, or vertical), and the chemical composi-

tion of the metal. For proper welding, aluminum

must be clean. All foreign matter must be removed

from the joint area so that the contaminants do not

become fluid from the heat of welding and flow into

the joint. Cleaning is most effective just before

welding; however, the welding supervisor can set a

suitable time limit based on shop conditions and

requirements of the product. Three methods are

commonly used to clean aluminum: solvent decreas-

ing, mechanical cleaning, and chemical etch

cleaning.

(1) Solvent decreasing to remove grease, oil,

dirt, and loose particles is most effective when the

metal surface is smooth and when contaminants are

not tightly adhered. Solvents include a wide range of

commercial products — e.g., acetone and cloro-

thene NU. But one should not use hydrocarbons

such as carbon tetrachloride and trichloroethylene;

these break down in the presence of the welding arc

to form highly toxic gases such as phosgene. Safety

precautions should be observed when using all

solvents.

(2) Mechanical methods of cleaning include

wire brushing, scraping, filing, planing, grinding,

and rubbing with steel wool. Because these methods

are costly, they should be used only for the weld

6-1

TM 5-805-7

areas. wire brushing may be done with a hard brush

or power rotary brush. Both types should have stain-

less steel bristles. These brushes must be kept clean;

when the bristles become dirty, they must be

degreased with solvents like those discussed above.

Before brushing, the joint area should be degreased.

If this is done, the brush will stay clean and will not

drive contaminants into the aluminum surface. Bur

nishing the aluminum surface can also entrap con-

taminants; therefore, only light pressure should be

used for power brushing. Cleaning by grinding is

best done with an open-coat aluminum oxide disk

(80 grit). This process is especially useful for remov

ing the heavy oxide film associated with water stain-

ing; wire brushing and chemical etching are not

effective. After mechanical cleaning, the metal

should be degreased.

(3) Chemical etching, which is useful for batch

cleaning, produces a surface free from contaminants

and heavy oxide films. However, etched surfaces

tend to be more absorptive than before. Thus, they

can be recontaminated if not protected and should

be cleaned just before welding.

(4) Following improper procedures — particu-

larly when cleaning — can produce defects in the

weld joint. These include porosity, tungsten inclu-

sions, incomplete fusion, inadequate joint penetra-

tion, undercutting, and cracking. Limitations on

various defects are governed by the ASME Boiler

and Pressure Vessel Code or military specifications;

whether a defect is severe enough to be unaccept-

able depends on the function of the finished

product.

c. Cracking. Sensitivity to weld cracking largely

depends on the weld metal’s composition. Both base

metal and filler alloy composition affect the result-

ing weld bead composition, and the welding heat

input affects the relative percentages of base metal

and filler metal in the weld bead. Furthermore, joint

design can significantly influence the relative per-

centage of base metal melted. In most alloy systems,

there are one or more regions of maximum crack

sensitivity. If the base metal composition has a high

cracking sensitivity, then filler alloys containing

high percentages of magnesium are used. This

changes the composition so that the weld metal is

less sensitive to cracking. Minor alloying elements

also change weld crack sensitivity. In particular,

grain-refining elements such as Titanium and Zirco-

nium are frequently added to reduce the cracking

tendencies of filler alloys. Minor amounts of copper

in an aluminum-magnesium-zinc alloy greatly

increase crack sensitivity. The copper contributes to

the formation of low-melting phases that segregate

at grain boundaries. Shrinkage stresses during weld

solidification can then cause boundary separation

before this low-melting phase solidifies.

(1) Crater cracks. Crater cracks are most often

encountered in aluminum welding. These are small

checks or crow’s foot defects which occur during

solidification after the welding arc has been broken

Such cracks may be small but are very serious since

they are usually at the end of a weld, where stress

concentration or “end effect” is most pronounced.

The number of crater cracks can be limited with

good welding practice. This usually involves proper

manipulation of the torch or filler, or both. The

technique most often used is to break and restart the

arc several times so that the shrinkage pipe in the

center is filled. In addition, run-out tabs are often

used to prevent crater cracks. The welder should

check carefully for these cracks, and should remove

them before rewelding. It is very hard to remove a

crater crack by remelting the weld.

(2) Longitudinal cracking. Cold longitudinal

cracks are not usually found in aluminum welds, but

hot cracks can sometimes occur when the metal is

passing between the liquidus and solidus tempera-

tures. These cracks usually are caused by incorrect

filler alloy, too low or too high a welding rate, and

incorrect edge preparation or joint spacing. Cold

cracks which occur below the solidus temperature

usually result w-hen too small a weld bead is laid

down. Cold cracks can be eliminated by a weld bead

large enough to withstand the cooling stresses

encountered during solidification.

d. Other defects. Other defects can be introduced

into the weld metal if an improper weld process or

technique is used. These defects include porosity,

tungsten inclusions, incomplete fusion, inadequate

joint penetration, and undercut. Paragraph 4-2e dis-

cusses incomplete fusion, inadequate joint penetra-

tion, and undercutting. This information applies to

aluminum as well as stainless steel.

(1) Porosity. Shrinkage porosity, associated with

overheating, and gas porosity are common defects in

welds. Spherical gas pores are found most often:

hydrogen is accepted as the major cause of porosity

in aluminum welds. Hydrogen usually results from

water or hydrocarbon contamination of the base

plate, filler wire, shielding gas, or arc column. The

size and number of gas pores for an existing hydro-

gen concentration vary with the weld metal’s solidi-

fication rate. Porosity formation is a nucleation and

growth process. At fast solidification rates, there is

not enough time for the nucleation step, and no

pores can be seen -- even at high hydrogen concen-

trations. At slower solidification rates, pore nuclea-

tion and some growth occur, but the bubbles are

trapped in the freezing metal before escaping. At

6-2

TM 5-805-7

slower and slower solidification rates, more time is

available for pores to grow and for gas to escape

from the molten pool. When solidification rates are

slow enough, all gas escapes and no porosity remains

in the weld bead. Random, scattered porosity that is

usually detected radiographically has little effect on

the mechanical properties. Of course, larger

amounts of gross porosity reduce the metal’s cross-

sectional area and lower the weld’s strength.

Aligned or layered porosity has a greater effect on

mechanical properties. Microporosity, too small to

be detected by standard radiographic techniques,

typically occurs in layers along the weld fusion line.

This defect lowers mechanical properties

considerably.

(2) Tungsten inclusions. Tungsten inclusions

occur only when the GTAW process is used. The

tungsten becomes trapped in the molten weld metal

because of two transfer processes. If the electrode’s

diameter is too small, the welding current melts too

much of the end, and any mechanical jostling of the

torch will cause a droplet of tungsten to be trans-

ferred to the weld puddle. Tungsten also can be

transferred if the electrode is touched to the weld

metal. To prevent tungsten inclusions, electrodes

with the correct diameter and with the proper taper

ground on the end should be used.

6-3. Joint design

Weld joints are prepared mechanically by machin-

ing, grinding, or plasma cutting. Before welding, the

joint surfaces must be cleared of all foreign materials

such as paint, dirt, scale, or oxide; solvent cleaning,

light grinding, or etching can be used. The joint

surfaces should not be nicked or gouged since this

can hinder welding. The AWS Welding Handbook,

Chapter 69, “Aluminum and Aluminum Alloys” has

a section on designing joints for welding. The theory

and practice of designing aluminum structures are

discussed; joint accessibility, edge preparation, and

stress distribution are covered.

6-4. Methods of welding aluminum alloys

The best welds result from careful cleaning of the

joint, proper selection of filler wire, and good weld-

ing practice. Aluminum alloys can be welded by sev-

eral processes. The choice depends on conditions

such as thickness and size of parts, location and posi-

tion of weld, number of similar welds, production

rate required, finish and appearance desired, and

type of aluminum alloy. The welding processes

which have been successful are gas, carbon arc,

atomic hydrogen, GTAW, and GMAW. The inert

shielded-arc welding process can be used in all posi-

tions, including overhead. Aluminum alloys for cryo-

genic applications are welded by either the GTAW

or the GMAW processes. This manual discusses only

the inert shielded-arc welding processes, the most

versatile and commonly used for field fabrication.

Preheating the weld joint before welding is not rec-

ommended. But if ambient temperatures are low, a

preheat of not more than 300 “F can be applied to

the joint before welding. The properties and metal-

lurgy of aluminum alloys are almost always affected

adversely by elevated temperatures, Therefore

preheating is not recommended, and welding heat

should be applied as briefly as possible.

6-5. Gas metal-arc (GMAW)

Use of GMAW is increasing for shop and field appli-

cations because of the economics of the process.

There is less downtime for electrode changes, much

less loss due to stub ends and spatter, and much less

interpass cleaning required. GMAW can be used in

all positions, with either short circuiting transfer or a

pulsed voltage power supply. No flux is required for

welding aluminum with the GMAW process. This

eliminates costly flux removal and the possibility of

post-weld corrosion due to flux residue. Another

outstanding characteristic of the GMAW process is

its use of high welding current densities. Current

densities on the wire commonly range from 60,000

to 300,000 amperes per square inch. These high

current densities, coupled with a very efficient heat

transfer in the arc, result in higher welding speeds,

less distortion, lower welding costs, better mechani-

cal strength, and better corrosion resistance than

can be obtained with any other arc welding process

on aluminum. High current densities and the effi-

cient heat transfer in the arc also produce deep pen-

etration. This makes the process good for fillet welds

and reduces the need for edge preparation. For

more details, refer to chapter 3.

a. Electrode classification system. The classifica-

tion codes for GMAW electrode wire consist of an E,

an R, and four digits in the configuration ERXXXX.

The prefix R indicates that the material is suitable

for use as a welding rod, and the prefix E indicates

suitability as an electrode. These filler metals can be

used as electrodes in GMAW and as welding rods in

GTAW; both letters (ER) indicate suitability either

as a welding rod or an electrode. So, an electrode

which meets the test prescribed in AWS A5.10

always can be used as either an electrode or a weld-

ing rod. The four numbers in the electrode classifi-

cation system refer to the alloy chemistry of the rod

or electrode. For example, an ER1100 classification

6-3

TM 5-805-7

would be an electrode or rod having a chemical

make-up equivalent to the 1100 alloy of aluminum.

b. Chemical requirements. AWS A5.10 contains

the chemical requirements for GMAW electrodes.

The proportions - of elements are similar in elec-

trodes and base metals with the same designation.

All chemical analyses are based on the as-manufac-

tured electrode wire.

c. Weld metal mechanical properties. For alumi-

num weld metal, AWS A5.10 specifies only ductility

as measured by the bend test, but not strength or

impact resistance levels.

d. Shielding gas. Helium and argon are the shield

gases for the CMAW process. Argon is used more

often now, but the availability and use of helium are

increasing rapidly. Because of helium’s low density,

a greater volume is required to produce the neces-

sary shielding. But deeper weld penetration is possi-

ble because of helium’s higher ionization potential.

Argon is better for manual welding because of the

arc instability y with pure helium. Helium/argon mix-

tures are being used more for semiautomatic weld-

ing, while both mixtures and pure helium are widely

used for automatic welding. To obtain adequate

weld penetration, helium alone — or a mixture of

helium and argon — may be preferred for welding

very heavy sections (more than 2 inches), This mix-

ture, 75 percent helium and 25 percent argon, is

commonly used and is available premixed.

e. Recommended filler metals for aluminum alloy

welding. The aluminum alloys are listed by the AA

specification numbers in the table entitled “Guide to

the Choice of Filler Metal for General Purpose

Welding,” appendix 1 of AWS A5.10. They are also

in the AWS Welding Handbook, Chapter 69, “Alu-

minum and Aluminum Alloys” and ASM Metals

Handbook, Volume 6, Arc Welding of Aluminum

Alloys.

6-6. Gas tungsten-arc (GTAW)

GTAW of aluminum is done with AC and superim-

posed high frequency in an atmosphere of argon gas.

In some industries, GTAW with DC straight polarity

and helium gas is receiving increased attention. DC

GTAW is done only with very low currents because

of overheating in the electrode. However, this pro-

cess is seldom used because of the accumulation of

tungsten inclusions noted in paragraph 6-2. As with

the GMAW process, GTAW does not use fluxes; the

welding arc in argon gas removes the aluminum

oxide film from the surface of the metal, and the

argon shield prevents it from reforming. GTAW

welds have good appearance and require little, if

any, grinding or finishing. The GTAW process can

produce X-ray quality welds in all the weldable alu-

minum alloys. Under proper conditions, GTAW

welds may have a sounder structure than welds

made with most other processes. Excellent penetra-

tion is easily obtained on butt welds that have been

properly prepared. However, care and experience

are required to obtain adequate penetration on fillet

and lap welds since there is a tendency to bridge the

root unless adequate current and a short arc are

maintained, AC GTAW is usually confined to thick-

nesses below 1/4 inch. The GMAW process or DC

straight polarity GTAW is generally for thicker sec-

tions. GTAW welding is normally used for most pipe

welding, for joints where abrupt changes in direc-

tion of the weld are encountered, and almost always

for welding aluminum less than 1/16-inch thick.

High quality welds can be made in all positions. For

additional information on welding process, see chap-

ter 3.

a. Electrode classification system. The classifica-

tion code for the GTAW filler rod consists of an E,

an R, and four digits in the configuration ERXXXX.

The letter E indicates that this is an electrode mate-

rial, and the R indicates that it is a welding rod.

Since these filler metals can be used as GMAW elec-

trodes as well as filler rods for GTAW, both letters

are used. The four-digit number, such as 1100 in

ER1100, designates the chemical composition of the

filler metal. The specification for these electrodes is

in AWS A5.10.

b. Chemical requirements. The chemical composi-

tions for GTAW welding rods are listed in AWS

A5.10. The proportions of elements are similar in

electrodes and base metals with the same four-digit

designation. All chemical analyses are based on the

as-manufactured welding rod.

c. Weld metal mechanical properties. For alumi-

num weld metal, AWS A5.10 specifies only ductility

as measured by the bend test, but not strength or

impact resistance levels.

d. Shielding gas. Two shield gases are used with

the GTAW process: pure argon and pure helium.

Argon is for thicknesses of 1/4 inch and less. Pure

helium is for thicker material when DC straight

polarity is used, and for machine welds.

e. Recommended filler metals for aluminum

alloys. The aluminum alloys are listed by AA specifi-

cation numbers in the table entitled “Guide to the

Choice of Filler Metal for General Purpose Weld-

ing” in AWS A5.10, Appendix 1. A comprehensive

list is also in the AWS Welding Handbook, Chapter

69, “Aluminum and Aluminum Alloys” and ASM

Handbook, Volume 6, “Arc Welding of Aluminum

Alloys.”

6-4

TM 5-805-7

CHAPTER 7

WELDING FOR SPECIAL APPLICATIONS

7-1. General

This chapter discusses welding applications for con-

crete reinforcing steel bars, railroad and crane rails,

castings, and composite materials. For these applica-

tions welding procedures must be qualified by suit-

able tests (appendix B), and persons skilled in the

specific process being used must do the welding.

7-2. Reinforcing steel bars

The widespread use of large-diameter and high-

strength reinforcing bars has made welded splices

very important. Welding is required where it is hard

or impractical to overlap bars and rely on the sur-

rounding concrete to transmit the load from one bar

to the other. Yet many of the reinforcing steels are

classified as hard to weld because of unfavorable

chemical composition (a high carbon equivalent).

Some specifications prohibit arc welding of reinforc-

ing steels whose carbon contents exceed 0.50

-- percent.

a. Procedures. Welded splices in reinforcing steel

bars have been used successfully since the middle

1930s. SMAW and thermit welding have been the

most popular methods of joining reinforcing bars for

field construction; the pressure gas and SAW pro-

cesses are for shop welding. GMAW and FCAW also

have been used successfully in the past few years,

(1) When reinforcing bars for concrete are to be

welded, one must determine the steel’s composition

and matching welding procedures, However, it is

hard to positively identify new and used reinforcing

bars, especially those to which splices are being

made so that a structure can be enlarged or modi-

fied. Even after positive identification of the rein-

forcing bar, the question of steel chemistry may

remain; reinforcing bars usually conform to ASTM

standards, which base the requirements on physical

properties and often do not specify steel chemistry.

(2) Welding should conform to AWS D12.1.

This specification deals with permissible stresses,

including unit stresses in welds; effective weld areas,

lengths, and throat thicknesses; structural details for

welding transitions in bar sizes, splice qualifications,

indirect butt splice details, and lap welded splice

details; and interconnections of precast members.

AWS D12.1 also discusses workmanship, technique,

qualification, and inspection of the joints.

b. Strength requirement, The strength of welded

splices in reinforcing steel bars can be determined

by the ultimate strength method or the working

stress method. AWS D12.1, table 2-2, describes the

type of joint and weld, the base metal used, and the

two methods of determining strength for both direct

and indirect butt splices. The requirement for transi-

tion strength levels is also discussed in American

Concrete Institute (ACI) 318.

c. Welding processes. Joints in reinforcing steel

bars can be made in several ways: SMAW, GMAW,

FCAW, thermit welding, or pressure gas welding.

AWS D12.1, section 5, details the procedures to be

used with the various welding processes. AWS

D12.1, table 5.1, shows the various types of elec-

trode materials to be used with the three arc weld-

ing processes. Thermit and pressure gas welding do

not require these filler metals. AWS D12.1, table

5.2, shows the preheat temperatures to be used for

various carbon equivalents for reinforcing bars of

different sizes.

d. Mechanical butt splices. Butt splices in rein-

forcing steel bars can also be made mechanically. A

splicing method has been developed which uses the

exothermic process; molten filler metal is put in the

annular space between the bar and high-strength

steel sleeve with an inside diameter larger than the

overall diameter of the bar. Since the strength of the

joint does not depend on fusion of the filler metal to

the reinforcing steel or the sleeve, this is classified as

a mechanical joint rather than a welded splice,

e. Contract specifications. Contract specifications

should include requirements for procedure qualifi-

cation, welder or welding operator qualification, and

inspection. The inspection should cover the materi-

als, the equipment necessary to conduct the welding

procedure, the qualifications of the welder or weld-

ing operator, and the completed work and records,

The qualification tests must be conducted on the

same material that will be used in the actual con-

struction. Requirements for the welding procedure

should cover the material specification, the welding

process to be used, the position of the weld, the

filler metal classification, and the type of pass (sin-

gle- or multi-pass). The procedure should also

include requirements for a preheat-interpass tem-

perature and a post-weld heat treatment, if

required.

7-1

TM 5-805-7

7-3. Rail intervals along the track, allow 3/8-inch movement

a. Advantages of welding. Welding railroad and of each rail end without bending the joint bolts.

These buffer rails make adjustments easier when ‘-

crane rail joints offers several advantages. Continu-

ous rails need less maintenance and wear less than continuously welded rail is laid at temperatures

rails that have joint ends with bolted connections. above or below the mean.

Loads roll smoothly from joint to joint. Most railroad

rail is welded in-shop in l/4-mile lengths by either

pressure gas welding or flash welding. Welding in

the field can be done using the exothermic process

described in the AWS Welding Handbook, section 2.

b. Exothermic welding. Exothermic welding is the

only rail welding process covered in this manual,

since the other processes are primarily limited to

shop welding. For exothermic welding, the ends of

the rails must be clean; the joint faces parallel, prop-

erly gapped, and aligned; and the joint preheated.

However, production joints made in the shop or in

the field do not necessarily produce consistent

strength, so the following precautions should be

taken.

(1) Detailed welding procedures must be pre-

pared. All procedures for production welding must

be qualified before welding starts. Completed welds

should be visually inspected. If there are blowouts

or voids, the welded joint should be replaced.

(2) Visual inspection must not be used for

acceptance of the completed weld. Internal defects

such as lack of fusion, slag inclusion, porosity, and

cracks might not be visible. Unfortunately, no meth-

ods are entirely suitable for inspecting rail welds

made by the exothermic process.

(3) Radiographic and ultrasonic inspection must

be included in contract specifications. However,

these approaches are not completely satisfactory. In

radiographic examination, excess metal must be

removed from the web of the rail and the joint

ground smooth. However, since varying thicknesses

are still involved, this method is hard to use and

results may be inconclusive. portable ultrasonic

inspection equipment is commercially available; but

it is very sensitive if improperly set up and may

indicate nonexistent or insignificant defects. Mag-

netic particle inspection is used for gas-pressure-

welded and flash-welded rail but is not as suitable

for rail welds made by the exothermic process. Rail-

road personnel generally use Sperry Rail Detector

cars to inspect rails when the track is being used.

(4) Room for thermal expansion must be pro-

vided when continuously welded rail is designed and

constructed. This is normally done by restraining

the rail by joint-bar friction at the ends and then

subjecting it to accumulated restraint from succes-

sive ties. Rails are usually laid so as to give zero

restraint at the anticipated mean temperature. Short

buffer rails, which are frequently installed at regular

7-4. Steel castings

Generally, the weldability of steel castings is compa-

rable to that of wrought steels. Cast steels are usu-

ally welded in order to join one cast item to another

or to a wrought steel item, and to repair defects in

damaged castings. The weldability of steels is pri-

marily a function of composition and heat treatment.

Therefore, the procedures and precautions required

for welding wrought steel also apply to cast steels of

similar composition, heat treatment, and strength.

Welding cast steels can sometimes be simplified by

first considering the load in the area being welded

and the actual strength needed in the weld. Castings

are often complex; a specific analysis may be

required only for part of the entire structure. When

welding a section of steel casting that does not

require the full strength of the casting, one can

sometimes use lower-strength weld rods or wires, or

the part being welded to the casting can be of lower

strength and leaner analysis than the cast steel part.

Under such conditions, the deposited weld metal

usually has to match only the strength of the lower-

strength member. With heat-treatable electrodes,

the necessary welding sometimes can be done

before final heat-treating. After being subjected to

an austenitizing treatment (heating above the upper

critical temperature), weld deposits with carbon

contents less than 0.12 percent usually have lower

mechanical properties than they have in the as-

welded or stress-relieved condition.

a. Weld joint design for structural welds. Joint

designs for cast steel weldments are similar to those

used for wrought steel. AWS D1.1, Section 2 con-

tains design criteria for welded connections and a

list of prequalified joint designs. Any other type of

joint design must be qualified before being used in

the structure. When designing a welded connection,

one should consider the type of weld process that

will be used, the strength of the filler metal, and the

welder’s access to the joint,

b. Recommended filler metals. The choice of elec-

trode filler metal is based on the type of cast steel

being used, the strength needs of the joint, and the

post-weld heat treatment. When welding carbon or

low-alloy cast steels, the electrodes recommended

for comparable wrought steel plate should be used,

When cast austenitic stainless steels are joined to

either cast or wrought ferritic materials, the proper

filler metal depends on the service conditions. If the

7-2

TM 5-805-7

service temperature is low (below 600oF) and the

stresses are moderate, a high-alloy austenitic stain-

less steel, such as Type 309 or 310, is generally

used. For service conditions under higher tempera-

tures and stress, the high-nickel welding materials

(70 percent Nickel-15 percent Chromium) are bet-

ter because their thermal expansion is closer to that

of the ferritic materials. High-nickel weld metal

retards carbon migration; and this weld metal should

be used with a technique to reduce nickel’s dilution

of the ferritic material.

7-5. Dissimilar combinations

Fabrication procedures often combine cast austen-

itic and ferritic steels, or cast austenitic materials

and wrought ferritic materials. Each combination

presents distinct problems. Dissimilar metals are

often used for surfacing cast carbon steels. Here the

problem is to select a process and technique causing

minimum dilution. This insures freedom from

underbead and weld cracking and improves the

quality of the surfacing deposit. The proper tech-

niques and materials are similar to those for wrought

materials. AWS, sources of welding equipment, and

metal suppliers can provide more information about

the successful welding and satisfactory services of

weldments of many of these combinations. Data not

available from these sources may have to be

obtained by testing.

7-6. Coated and clad materials

a. Composite materials. Composite materials are

often used in structures to obtain special properties.

Generally, a thick supporting layer of base metal is

bonded to a thin layer of another metal, often more

expensive, which has the desirable properties.

These may include corrosion resistance, thermal or

electrical conductivity, abrasion resistance, or deco-

rative appeal. The composites may be obtained by

several processes, such as plating, cladding, lining,

and weld overlay. When welding before coating,

one must consider how the weld metal and coating

metal can affect each other. For example, the weld-

ing operation may damage the coating, or the coat-

ing may adversely affect the weld. When welding

cladplate and applied-liner construction, the opera-

tor must control the dilution of weld metal where

the two metals meet. Joint penetration, electrode

selection, welding process, and welding techniques

are important considerations in welding clad materi-

als and applied liners. Detailed information is in the

AWS Welding Handbook, section 5.

b. Galvanized steel. When possible, welding

should be done first, since galvanizing over welds is

easy. Steel already galvanized can be welded with

either the electric arc or gas welding processes, but

the zinc coating next to the weld maybe damaged so

much that it will not protect the steel. Thus, a coat-

ing must be applied to the welded joint to protect it

from corrosion. The joint might be designed so that

the galvanized steel is subjected to tensile stresses

during welding or upon cooling. The stressed metal

could fracture when the molten zinc or zinc vapor

penetrates into the welded joint. Before welding,

therefore, the zinc should be removed from all joints

and surfaces of strength members. This should be

done far enough from the expected toes of the weld

to prevent such embrittlement. Light-gauge galva-

nized sheet metal may be welded by GMAW with-

out substantially damaging the galvanized coating;

this can be done with phosphor-bronze filler metal,

or the carbon arc process can be used with or with-

out silicon-bronze filler metal. More information on

welding zinc-coated steel is in AWS D19.0.

7-3

CHAPTER 8

INSPECTION PROCEDURES

8-1. General

Weld joints are inspected for two reasons. First,

inspection is used to determine the quality of spe-

cific joints and to insure this quality meets the appli-

cable specifications. Weld defects are detected and

their location noted, so the unacceptable part of the

weld can be removed and replaced with sound weld

metal. The second need for weld inspection is just as

important but is less frequently recognized. Weld

inspection serves as a quality control on the welding

operators or welding procedures. Records of how

often various types of defects occur can show when

changes in welding procedures are needed, when

poor welding practices are being used, or when the

welders or welding operators should be requalified.

A responsible fabricator will depend on inspection

records to provide advance notice that the welding

operations need attention. The fabricator will be

able to correct problems soon enough to prevent the

lost time and high costs of frequent repairs.

8-2. Qualification of personnel

Personnel doing nondestructive testing must be

qualified according to the current requirements of

the ASNT SNT-TC-1A. If applicable, nondestructive

testing personnel can be certified under MIL-STD-

410, or MIL-STD-271.

8-3. Inspectors

The inspector must uphold all quality criteria as

defined in applicable specifications and standards

and must judge whether the weldments inspected

conform in all respects to the specifications. The

inspector must know the limitations of the testing

methods, the material, and the welding process. Ide-

ally, the inspector also must have integrity and be

willing to accept the responsibilities of the position.

8-4. Inspection

Virtually every inspection method available has

been used to examine welds: visual, magnetic parti-

cle, liquid penetrant and ultrasonic, destructive,

leak testing, and radiographic --- X-rays and radio-

isotopes. Acoustic emission and eddy current

inspection have been used in production testing, but

are not yet being used in field inspections. Table 8-1

lists the advantages and disadvantages of various

inspection techniques. The method and extent of the

inspection vary with the nature of the work and the

criticality of certain joints. The following factors

should be considered in selecting nondestructive

test methods for weldments:

—Material to be tested.

—Joining process.

—Geometry of material.

—Possible or expected defects and their

orientation,

—Economic considerations.

Some weldments may require combinations of two

or more inspection methods to provide adequate

evaluation. Questionable results from one method

often may be verified by another method. Destruc-

tive testing is used primarily for the qualification of

welding procedures,welders, welding operators,

and sometimes for quality control.

a. Inspection procedures. The quality, integrity,

properties, and dimensions of materials and compo-

nents can be inspected with methods that do not

cause damage. The following are nondestructive test

methods:

—Visual inspection.

—Penetrant inspection.

—Magnetic particle inspection.

—Radiographic inspection.

—Ultrasonic inspection.

—Leak testing.

It is particularly important to inspect tank welds and

root passes of multi-pass welds before more weld

metal is deposited. These welds are thinner than the

subsequent weld passes and therefore more likely to

crack. If there is a crack, it may propagate with

subsequent passes. If this happens, the entire weld

must be removed and the joint rewelded. It is less

expensive and quicker to replace defective tack

welds and root passes before more weld metal is

added. Thus, these welds should be inspected as

soon as they are made. Follow-up inspection of root

passes is important because subsequent passes may

seal a crack so tightly that it cannot be detected by

visual inspection. Inspection of the completed weld

would indicate it is sound.

8-1

TM 5-805-7

b. Repair of defective welds. When a defective

weld is removed and the joint rewelded, the repair

weld should be inspected in the same way as the

original weld. The surfaces of the joint from which

the defective metal was removed should be

inspected to make sure the defect is completely

gone. Cracks should be checked very carefully. If

part of a crack is allowed to remain, it may propa-

gate through a repair weld; this must be avoided. A

series of inspections and metal removals may be

needed.

8-5. Visual inspection

Visual inspection, which is the most widely used

inspection method, is also the quickest, easiest, and

cheapest. The only equipment commonly used is a

magnifying glass (1 OX or less) and a flashlight or

extension. Other tools, such as a borescope and den-

tal mirrors, are useful for inspection inside vessels,

pipe, or confined areas. Visual inspection is always

required in weld evaluation. However, it will not

reveal interval defects or minute surface defects.

a. Examination prior to welding. Before welding,

the faces and edges should be examined for lamina-

tions, blisters, scabs, and seams. Heavy scale, oxide

films, grease, paint, oil, and dirt should be removed.

8-2

Edge preparation, alignment of parts, and fit-up

should be checked. Welding specifications should

be specific and state that all weld joints must be

inspected for compliance with requirements for

preparation, placement of consumable inserts, align-

ment, fit-up, and cleanliness.

b. Examination of welds during welding. Specifi-

cations should state that welds must be examined for

conformance to the qualified welding procedure,

detection of cracks in root pass, weld bead thick-

ness, slag and flux removal, and preheat and

interpass temperatures, where applicable.

c. Examination of welds after welding. Specifica-

tions should state that welds must ‘be examined for

cracks, contour and finish, bead reinforcement,

undercutting, overlap, and size of fillet welds. A

weld is considered acceptable by visual inspection

if:

(1) The weld has no surface flaws such as cracks,

porosity, unfilled craters, and crater cracks, particu-

larly at the end of welds.

(2) The weld metal and base metal are fused.

The edges of the weld metal should blend smoothly

and gradually into the adjacent base metal. There

should be no unacceptable overlap or undercut. —

(3) The weld profiles conform to referenced

standards and specifications. The faces of fillet welds

may be slightly convex, flat, or slightly concave, as

determined by use of suitable gages or templates (fig

8-1). The minimium size of each fillet leg is speci-

fied on the applicable drawings or welding proce-

dure. For butt welds, the amount of weld bead

reinforcement or the height of the surface of the

weld above the base metal surface should be no

greater than the welding specification allows (fig

8-2). (These standards should be developed early in

a job, and should represent acceptable, borderline,

and rejectable conditions. When there are several

critical joints, a separate standard may be prepared

for each.) The objective of all inspection methods is

to reveal any flaws or defects that may affect a part’s

service performance. Therefore, a joint should be

cleaned to remove anything that would hinder

inspection; e.g., slag and oxide films. Care should be

taken when a cleaning method such as shot-blasting

is used. Fine cracks and similar imperfections may

be sealed on the surface and made invisible. In vis-

ual inspection, it is essential to correctly interpret

and evaluate discrepancies in the appearance of

welds. Thus, the inspector needs to understand the

welding process in order to evaluate the quality of a

weld.

8-6. Magnetic particle inspection

Magnetic particle inspection is a nondestructive

method of detecting cracks, seams, inclusions, segre-

gations, porosity, lack of fusion, and similar flaws in

ferromagnetic materials such as steels and some

stainless steel alloys. This method of inspection can

detect discontinuities which may be too fine to be

seen with the naked eye; it can also detect some

subsurface defects, depending on the depth of flaw

cle inspection is advantageous because it can be

used on any magnetic material and is a rapid, inex-

pensive, and very reliable method when used by

trained inspectors. The main disadvantage is that it

applies only to magnetic materials and is not suited

for very small, deep-seated defects. The deeper the

defect is, the larger it must be for detection. Subsur-

face defects are easier to find when they have a

crack-like shape, such as lack of fusion in welds.

Welds with rough surfaces may present difficulties.

The process’ sensitivity is decreased by this rough-

ness, which mechanically interferes with the pattern

formed by iron oxide particles (see a below).

a. Principles of magnetic particle inspection. The

part to be inspected is magnetized by passing

through it a low-voltage, high-amperage electric

current, or by placing it in a magnetic field. Any

discontinuities such as cracks or lack of fusion dis-

rupt the magnetic field that has been established.

Electrical poles form at the ends of the flaws (fig

8-3). Fine magnetic particles applied to the surface

of the part are attracted to these electrical poles.

The concentration of particles can be seen and the

flaw located.

(1) The ease with which a magnetic flux can be

developed in a material is known as its permeability.

The property of any magnetic material to keep or

retain a magnetic field after the magnetizing current

is removed is called retentivity. Metals which lose

most of their magnetism as soon as the magnetizing

current is removed have low retentivity. Usually a

magnetized metal that has high permeability has low

retentivity, while a metal with a low permeability

has high retentivity. Construction steels generally

have low retentivity.

TM 5-805-7

TOE

(SIZE

8-4

TM 5-805-7

MAGNETIC

LINES

FORCE

(2) DC, AC, and half-wave rectified current

may be used for magnetization. High-amperage,

low-voltage current is usually employed. If only sur-

face defects are to reinspected, AC can be used.

DC isused for the detection of subsurface disconti-

nuities because the current penetrates throughout

the part. Maximum sensitivity is provided by using

half-wave rectified, single-phase current. The pul-

sating field increases the particle mobility and

enables the particles to lineup more readily in weak

(3) The magnetic particles may be applied to

the weld either as a dry powder or as a suspension in

a light oil. The particles used are carefully selected

iron oxide particles of the proper size, shape, mag-

netic permeability, and retentivity. Dry particles are

in powder form and may be obtained in gray, red, or

black for contrast. These particles are applied using

hand shakers, spray bulbs, shaking screens, or an

airstream. Wet particles consist of particles sus-

pended in a light petroleum oil or kerosene. They

leakage fields. The pulse peaks also produce a can be applied- by

higher magnetizing force, which is needed in the from aerosol cans.

inspection of welds.

dipping, immersing, or spraying

The particles can be colored or

8-5

TM 5-805-7

have a fluorescent coating for viewing with ultravio-

let light. Wet particles provide better control and

standardization of the concentration of magnetic

particles through control of the concentration of sus-

pension. The wet procedure is more sensitive for the

detection of extremely small discontinuities below

the surface. Excess powder should be removed with

a stream of air of just enough force to carry the

excess away without disturbing lightly held powder

patterns.

(4) A method of applying the bath or particles

after the magnetizing current has been turned off is

called the “residual method. ” This method of apply-

ing the particles is effective on materials that will

retain their magnetism, i.e., those having high reten-

tivity. Steel that is relatively high in carbon and

other alloys responds most favorably to this method.

Most construction steels, however, have low reten-

tivity and will not hold a strong enough magnetic

field for this method. The recommended method for

construction steels is the “continuous method”; mag-

netizing is done at the same time the inspection

medium or particles are applied. This method is par-

ticularly useful when inspecting low carbon or alloy

steels. Because of their low retentivity, the parts

cannot maintain enough residual magnetism to hold

the particles needed to indicate a defect. Whether

wet or dry continuous methods are used, the inspec-

tor must be careful not to wash or shake off the

magnetic particle indications. Excessive current

must not be used during magnetizing because this

may produce irrelevant indications. Because of the

strong field produced, the continuous method is

especially useful in locating subsurface defects.

(5) When current is passed through a coil which

is wrapped around a material, a magnetic field is

produced in that material. This is called longitudinal

magnetization. When clamps or prods are used to

pass the current through the material, the procedure

is called circular magnetization. The two methods

produce magnetic fields in different directions,

thereby permitting the inspector to examine a mate-

rial for discontinuities in all directions.

b. Equipment. Various types of magnetizing

equipment are available. Units with electromagnets

and permanent magnets are commonly used, but are

designed for locating surface cracks. Although such

a unit can locate some subsurface defects, its depth

of penetration is severely limited. Direct current

equipment provides the great depth of penetration

needed to detect subsurface flaws. Some equipment

has both full-wave and half-wave rectified direct

current (HWDC). HWDC is particularly suitable for

use with dry particles because the pulsating field

provides excellent mobility to the powder particles,

Since most construction steels have low retentivity,

demagnetization is generally not required; however,

most magnetic particle inspection units can demag-

netize after inspection.

c. Inspection procedures. The procedures

decribed substantially conform to ASTM E 138 and

ASTM E 709. MIL-I-6868 and the ASME Boiler and

Pressure Vessel Code, section V, also outline inspec-

tion procedures. The surface of the weld usually

does not require grinding or smoothing before test-

ing. However, if the edges of the weld are undercut

or-if the bead surface is extremely rough, the weld

should be ground smooth and the edges blended

into the base metal surface before magnetic particle

inspection. The surface should be cleaned of all

grease, oil, loose rust, or water because such materi-

als interfere with the particles which indicate

defects.

(1) The “prod method” of weld inspection is

widely used. Portable prod-type electrical contacts

are pressed against the surface of the material next

to the weld, as shown in figure 8-4. The prods

should not be spaced more than 8 inches apart. A

shorter prod spacing with a minimum of 3 inches

may be used to increase sensitivity. When the prods

are positioned, the operator turns the current on

and applies the magnetic particle powders. The cur-

rent is turned off before the prods are removed in

order to prevent arcing. At least two separate exami-

nations should be done for each area. The prods are

repositioned so that the lines of flux from one opera-

tion are approximately perpendicular to the lines of

flux from the previous operation. Contact clamps

sometimes can be used instead of prods.

(2) The weld must be examined immediately

after the excess powder has been removed and

before the position of the prods is changed. Surface

defects appear as sharp indications, while subsurface

indications are broad, diffuse patterns.

(3) Acceptance standards are written based on

the object’s intended use. Standards vary, but most

specify similar limits for possible defects.

8-7. Penetrant inspection

Penetrant inspection is a sensitive, nondestructive

method of locating minute flaws open to the surface

— for example, cracks, pores, and leaks. It is partic-

ularly valuable for examining nonmagnetic materi-

als, on which magnetic particle inspection cannot be

used. Penetrant inspection is used extensively for

exposing surface defects in aluminum, magnesium,

and austenitic stainless steel weldments, and for

locating leaks in all welds. Dye penetrant proce-

dures usually require ground surfaces, although

some “as-welded” surfaces can be inspected. —

8-6

TM 5-805-7

(Improper grinding can smear the surface and close

surface openings of the defects.) The efficiency of

the method depends on the inspector’s ability to

recognize and evaluate the visual indications of

flaws.

a. Principles of liquid penetrant inspection. In liq-

uid penetrant inspection, both visible and fluores-

cent, the surface of a material is coated with a film of

penetrating liquid (fig 8-5). The liquid is allowed to

seep into any flaws that are open to the surface, and

the excess surface film is removed. A developer is

then applied; it draws the penetrant from a disconti-

nuity to the surface so the inspector can see the

flaw.(1) Liquid penetrant inspection can be done

quickly and easily; it costs less per foot of weld

inspected than any other nondestructive method

except visual inspection. The initial cost of training,

equipment, materials, and supplies is much less than

that of any other inspection method. However, sur-

face porosity and improper surface cleanliness

reduce the sensitivity of the inspection technique;

contaminants such as water, oil, and grease can

cover or fill discontinuities so the penetrant does not

enter. Penetrant inspection methods are used to

check nonporous materials for defects open to the

surface. The following surface defects can be found

with penetrant inspection: all types of cracks in con-

nection with welding, grinding, fatigue, forging,

etc.; porosity; seams; laps; cold shuts; or lack of

bond between two metals. Since penetrant methods

can locate only surface defects, cleanliness is

extremely important.

(2) penetrant inspection is equally applicable to

both large and small weldments. In the petrochemi-

cal industries, pressure vessels and piping, which are

often made of nonmagnetic materials, can be

inspected for surface cracks and porosity by this

method. Penetrant inspection can be used to detect

cracks, pores, and leaks through the lining in clad

vessels. This method can be applied to all types of

welded linings. Shallow cracks and porosity can be

distinguished from those that extend through the

lining (leakers). The indications for all cracks and

porosity bleed out rapidly or spread upon applica-

tion of dry developer.

b. Equipment. The equipment used in penetrant

inspection is portable: aerosol cans of cleaner, dye,

and developer. When fluorescent penetrant is used,

a black light source in the 36-angstrom unit range

and a hood or dark area are required. Portable

inspection kits for field use are commercially

available.

Inspection procedures. The procedure

described substantially conforms to ASTM E 165.

(1) Either the visible or fluorescent dye pene-

trant method can be used between a series of

stringer welds or on a completed weld. There are

three types of penetrant: water washable, post emul-

sifying, and solvent removable. Intermixing these

penetrant materials is not permitted. Procedures for

inspection depend on the specific type of penetrant

and the method used; therefore, only a general

approach is outlined in this manual.

8-7

TM 5-805-7

(2) The surface must be clean and dry. The dis-

continuity must be free of oil, water, or other con-

taminants so that the void is open and the penetrant

can enter. The method of cleaning the weld area is

unimportant part of the test procedure.

(3) The penetrant is applied to the surface by

spraying or brushing. The inspector must allow

enough time for the penetrant to enter all disconti-

nuities. A minimum time of 10 minutes at a tempera-

ture of 60 to 125 degrees F is normally

recommended. The smaller the defect or the higher

the sensitivity required, the longer the penetrating

time must be.

(4) Excess penetrant can be removed from the

surface by wiping with an absorbent cloth, either

dry or moistened with a solvent. Removing the sur-

face penetrant by spraying with solvents gives a

clean surface; however, penetrant can be washed

out of defects if the spraying is not done very care-

fully. Therefore, this technique is not

recommended.

(5) The developer should be applied carefully

so it does not produce a coat so thick that indications

are masked. The developer acts as a blotter to draw

the penetrant to the surface, where it can be seen

with the naked eye or viewed under an ultraviolet

light (in fluorescent penetrant inspection). The

developer must be applied as soon as possible after

the penetrant removal operation; the time between

the application of the developer and interpretation

should be controlled ((6) below). The true size and

type of defect are difficult to appraise if the dye

diffuses too much in the developer. The recom-

mended practice is to observe the surface during the

application of the developer in order to see certain

indications which might tend to bleed out quickly. —

(6) Interpretation must be done within a speci-

fied time. The specification might indicate, for

example, that interpretation must be done no sooner

than 7 minutes and no later than 30 minutes after

application of the developer.

(7) Most acceptance standards specify similar

limits on cracks and linear indications, rounded indi-

cations of a specific size and quantity, or number of

indications in a given area.

8-8. Radiographic inspection

Radiographic inspection is a nondestructive testing

technique which involves taking a picture of the

internal condition of a material. This picture is pro-

duced by directing a beam of short wave-length

radiation (X-rays or gamma rays) through a material

that would be opaque to ordinary light. This radia-

tion exposes a film which is placed on the opposite

side of the material. When developed, the film

(called a radiograph) shows the presence or absence

of internal defects. Radiographic inspection is called

for in many specifications because it provides a per-

manent record. Different types of internal defects

can be identified, and flaws such as cracks, porosity,

lack of fusion, and entrapped slag can be differenti-

ated. Radiographic inspection has its limitations,

8-8

however. These include high initial cost, radiation

hazards, the need for highly trained technicians, and

the requirement that certain defects, particularly

cracks and lack of fusion, be correctly oriented with

respect to the beam of radiation (if the orientation is

incorrect, the defects will not be recorded on the

film).

a. Principles of radiographic inspection. Radiogra-

phy uses the penetrating power of radiation to

reveal the interior of a material. Radiation from a

source passes through an object and causes a change

in the film emulsion when the film is developed. The

amount of darkening of the film, referred to as den-

sity, depends on the amount of film exposure caused

by radiation penetrating the thick or thin sections of

the object. The procedure for radiographic testing is

shown schematically

TM 5-805-7

in figure 8-6. The cone of radi-

—

ation could also represent a gamma-ray capsule con-

taining radioactive material such as those listed in

table 8-2. Not all of the radiation penetrates the

weld. Some is absorbed, the amount depending on

the density and thickness of the weld and on the

material being inspected. A cavity, such as a blow-

hole in the weld interior, leaves less metal for the

radiation to pass through, so that the amount

absorbed by the weld will vary in the defective

region. These variations, if measured or recorded on

a radiation-sensitive film, produce an image that will

indicate the presence of the defect. In applying radi-

ographic inspection, care is required to insure that

the procedure is carried out properly. Inadequate

technique can result in poor sensitivity, irrelevant

indications, or other problems.

Table 8-2. Characteristics of Radioisotope Sources

b. Equipment. The equipment required for radio-

graphic inspection is either an X-ray machine or

gamma source, film, penetrameters, film developing

equipment, and viewing equipment, as described

below. In ASTM E 94, the table “Type of Industrial

Radiographic Film” lists film characteristics; the

table “Guide for Selection of Film” lists recommen-

dations for radiation sources and film types to be

used with a variety of alloys in different section

thicknesses.

(1) X-ray machines are available in a wide range

of sizes and voltage ratings. The kilovoltage rating

required depends on the thickness and type of metal

to be radiographed.

(2) Radioactive sources and x-radiation have

similar effects on radiation-sensitive film. The differ-

ence between the rays is the origin. X-ray radiation

is generated in an X-ray tube, while gamma radia-

tion is emitted from a radioactive isotope. Table 8-2

gives some of the more important characteristics of

radioisotopes. These figures are rough estimates,

but do show the relative positions of the sources in

order of their energy.

(3) Gamma radiography is used frequently in

construction work because no external power is

required, which makes it suitable for inspection in

remote areas; the cost of the equipment and source

is much less than that of X-ray equipment with a

comparable kilovolt range; the isotope equipment is

more easily transported; the equipment is rugged

8-9

TM 5-805-7

SOURCE OF X-RAYS

Figure 8-6. Radiographic setup.

and simple to operate and maintain; and confined

spaces can reinspected because of the small source

size. However, there are several disadvantages to

isotope sources. Among these is a severe radiation

hazard. These sources must be stored in locked,

shielded cases, and handled very carefully when

used. Personnel performing radiography must be

highly trained and must relicensed by the Nuclear

Regulatory Commission. The radiographs generally

have considerably less contrast than films exposed

by X-radiation. The cost and trouble of replacing

isotopes with short half-lives can be a factor in

deciding whether to use X-ray or gamma radiogra-

phy on a project.

(4) The image quality of a radiograph can be

shown by using a penetrameter. This is a piece of

metal similar to that being inspected. It is placed

near the weld on the source side during radiography

to determine the degree of sensitivity disclosed in a

radiograph. For example, if a penetrameter with a

thickness of 2 percent of the material to be

inspected can be seen on the radiograph, it means

that the radiograph contrast sensitivity is 2 percent

or better, since the radiographic technique

employed can show an object thickness difference of

2 percent or more. In most cases, 2 percent contrast

sensitivity is considered satisfactory. However, for

critical purposes such as nuclear components, pres-

sure vessels, and piping for compressed gasses and

8-10

TM 5-805-7

bridges, a lower percentage is desired. In other clas-

ses of work, a higher percentage maybe acceptable.

To demonstrate detail sensitivity, holes in the pene-

trameter are used; their diameters are, in terms of

effect, artificial flaws of known dimensions. The

holes are usually expressed in the thickness of the

penetrameter. Construction details of penetrame-

ters are shown in figure 8-7.

(5) The radiographic film must be Class 1, extra

fine grain, and Class 2, fine grain. Both classes of

film give high contrast. Extra fine grain film has

greater sensitivity than fine grain (i.e., reveal

smaller discontinuities). However, exposure times

may be as much as 50 percent longer since more

exposure to radiation is needed to develop an image.

Film holders must be flexible, and intensification

screens must be made of lead. Front screens should

be 0.005 inch and back screens 0.010 inch.

(6) Film processing equipment can be either

manual or automatic. Processing systems should con-

tain separate tanks for developing, short stop or

washing, fixing, and final washing. Film driers must

not cause processing defects.

(7) A densitometer or a density strip is needed

to make sure film density requirements have been

met. Density, a measure of the degree of blackness,

is a function of exposure time and intensity of the

radiation to which film is subjected. The radiogra-

pher controls these variables.

c. Inspection procedure. The procedure described

substantially conforms to ASTM E 94, ASTM E 142,

and AWS D1.1. Procedures are also outlined in

MIL-R-11470, MIL-STD-453, and the ASME Boiler

and Pressure Vessel Code, section V.

(1) Radiographs must be made by either the X-

ray or isotope radiation methods. If the level 2-2T

radiography- is required, all radiographs should

reveal discontinuities with thicknesses equal to or

greater than 2 percent of the thickness of the thin-

ner part joined by the weld being examined. In the

“2-2T” designation, the first digit 2 means 2 percent

sensitivity and 2T the diameter of the hole in the

penetrameter which must be clearly visible in the

radiograph. Class 1 or 2 film must be used. The film

must be clean and free of processing defects. It must

have a density of not less than 1.5 nor more than

4.0, although densities within the range of 2.5 to 3.5

are preferred. Radiographs will show:

(a) The smallest hole in each penetrameter as

specified in the specification.

(b) The radiograph identification and

location.

(2) Welds that are to be radiographed need not

be ground or otherwise smoothed for radiographic

testing unless the surface irregularities interfere

with the desired radiographic image. When weld

reinforcement or backing is not removed, shims of

the material being radiographed must be placed _

under the penetrameter. These shims must make the

total thickness of material between the penetrame-

ter and the film at least equal to the average thick-

ness of the weld measured through its reinforcement

and backing.

(3 Pnetrameters must be placed on the side of

the work near the radiation source adjacent and par-

allel to the weld, A radiograph identification mark

and two location identification marks, all of which

are to show in the radiograph, must be placed on the

material at each radiograph location.

(4) Film holders must be placed tightly against

the test item whenever possible. Shielding beyond

the film holder should be provided when practical.

The operator must use radiation detection devices,

including survey meters, film badges, and

dosimeters.

(5) Film must be processed so that the radi-

ographs are of high quality. Films containing

mechanical, chemical, or other processing defects

that could interfere with proper interpretation of

the radiograph are not acceptable.

(6) Radiographs are viewed using a high-inten-

sity light source that has adjustable levels from dim

to a brightness that penetrates without difficulty

radiographs with a density of 4.0. Radiographs must

be checked for proper placement of identification

numbers and penetrameters. All indications must be

interpreted and marked.

(7) The interpreter must be familiar with the

standards for acceptance or rejection. Most stan-

dards agree about the types of discontinuities which

are not acceptable, but there are some differences.

Defects such as cracks or zones of incomplete fusion

or penetration would be cause for rejection. Poros-

ity of one size or aggregate lengths might also be

cause for rejection, while other sizes or lengths

would be acceptable. Reference radiographs are

indicated in ASTM E 94, MIL-STD-779, and MIL-R-

45774.

8-9. Ultrasonic inspection

Ultrasonic inspection is a rapid, efficient, nonde-

structive method of detecting, locating, and measur-

ing both surface and subsurface defects in

weldments and/or base materials. An ultrasonic is an

energy wave form with frequencies above 20,000

Hertz. The ultrasonic wave is introduced into the

material being tested by a piezoelectric transducer

placed in contact with the test specimen. The ultra-

sound enters the specimen and is reflected back to

the transducer when it encounters an interface that

8-12

Table 8-3. Comparison of Ultrasonics With Other Techniques

Radiography

Porosity

2. Inclusions 2.

3. Large cracks 3.

4. Lack of fusion 4.

5. Lack of penetration 5.

6. Small cracks

could be a flaw or the back surface of the material.

These vibrations are converted to electric signals,

amplified, and displayed on a cathode ray tube

(CRT) screen as indications. Because of the high fre-

quency (above the range for the human ear), the

short wave-length allows small flaws to be detected.

Ultrasonics is one of the most commonly used tech-

niques for subsurface flaw detection in weldments.

Ultrasonic inspection is specified to detect both

internal and surface flaws in all types of welded

joints. Defects such as slag inclusions, porosity, lack

of fusion (cold shuts), lack of penetration (root

defects), and longitudinal and transverse cracks can

be detected. Since only one inspection surface is

usually required, many types of welded joints can be

satisfactorily inspected. When a flaw is found, it can

be measured and evaluated. Dimensions such as

depth, width, and length can be measured if one

surface is accessible.

a. Principles of ultrasonic inspection. Most

ultrasonic testing is performed with a single straight

or angle beam transducer depending on the design

of the weld joint to be inspected. The transducer,

sometimes referred to as a crystal or search unit, can

transform electrical voltage generated by the

ultrasonic unit into mechanical vibrations or ultra-

sound. The transducer also can convert the

returning vibrations from a test specimen into elec-

trical energy; they are displayed in this form on the

ultrasonic unit’s CRT. This capability to convert

from electrical energy to mechanical vibrations and

back again is called the piezoelectric effect. The

electrical signal striking the transducer, usually not

more than 1 microsecond in duration, makes the

transducer vibrate during the driving period. The

duration of the pulse is short, so that returning or

reflected echoes from defects or boundaries lying

close to the surface will appear as a separate indica-

tion, as shown in figure 8-8. Such a presentation is

called an A-scan and is a “time versus amplitude

display.” From the pip or pulse location on the CRT

time line and its height of amplitude, the relative

depth and size of the discontinuity can be estimated.

(1) Ultrasonic inspection has many advantages

over other methods. It is fast, and the equipment is

compact and portable. Unlike radiographic inspec-

tion, it involves no time delay while film is being

processed and poses no radiation hazard to persons

working in the inspection area. Indications of flaws

can be seen immediately on the CRT. Both internal

and surface flaws can be detected (though shallow

surface cracks are more easily and reliably detected

with magnetic particle or liquid penetrant). Since

there are no expandable materials, the inspection

can be performed faster and at a lower cost than

radiography. Certain types of defects not readily

detectable by other inspection methods can be

found by ultrasonics. By using calibrated standards

and a few calculations, the inspector can classify he

indications as irrelevant, acceptable, or unaccept-

able. Ultrasonic inspection has a higher sensitivity

level than does radiographic inspection. Ultrasonic

inspection is more sensitive to crack detection as the

material thickness increases; for radiographic

inspection, the opposite is true. Table 8-3 compares

ultrasonics and radiographic, magnetic particle, and

liquid penetrant inspection.

(2) Ultrasonic inspection has some limitations

that have restricted its use. Chief among these are

the difficulty in interpreting the oscilloscope pat-

terns and the need for standards to calibrate the

instrument. This procedure produces no permanent

records showing flaws and their location. A high

degree of operator skill and training is required to

interpret the oscilloscope patterns reliably. Flaws,

such as cracks, oriented parallel to the sound beam

may not be detected. This means a different

ultrasonic inspection technique must be used. The

8-13

TM 5-805-7

INITIAL

PULSE

8-14

TM 5-805-7

surface of the material must be free from weld spat-

ter and must be smooth enough to allow effective

coupling between the transducer and the material.

Surface roughness can cause scattering and absorp-

tion of the sound. Also, a rough surface will create

undue wear on the crystal surface of the transducer,

causing premature failure. A viscous coupling agent

such as glycerine is necessary to eliminate the com-

pressible air which prevents sound (mechanical

vibrations) from entering the material from the

transducer. The coupling agent can be any liquid,

grease, or paste which fills surface depressions or

pits.

(3) Two important considerations in selecting a

transducer are its diameter and operating frequency.

The higher the frequency, the greater the sensitivity

will be. This advantage may be offset if lower fre-

quencies are needed to penetrate coarse-grained or

very thick materials. Table 8-4 shows the ultrasonic

frequency ranges that may be used on various

applications.

(4) Transducers generally fall into three groups:

straight beam, angle beam, and surface wave.

(a) Longitudinal wave, sometimes called

straight beam, directs the sound waves into the

material in a direction perpendicular to the surface

of the part. This method is used mainly to detect

subsurface defects in base metals, but should be

specified for some weld inspection, as shown in fig-

ure 8-9.

(b) The angle beam method, sometimes called

shear wave, is usually the required procedure for

weld inspection. The vibrational wave is introduced

into the material at an angle of 30 to 80 degrees

from the perpendicular to the material surface. This

angle will vary with the material’s thickness. A lon-

gitudinal transducer is mounted on plastic wedges

cut at specific angles, usually 70, 60, or 45 degrees.

By varying the position of the angle beam search

unit with respect to the weld, flaws at any location in

the weld joint can be detected, as shown in figure

8-10.

version so that the refracted wave will travel along

the surface. Surface waves follow curved surfaces

and detect surface and near-surface defects. This

technique has many applications in industry, but is

seldom used for weld inspection.

b. Equipment. The equipment for ultrasonic weld

inspection is a pulse-echo-type ultrasonic test unit

that can generate, receive, and present on a CRT

screen pulses in the frequency range from 0.2 to 10

megahertz.

8-15

INSPECTION

ZONE

8-16

(1) Transducers will consist of straight beam and

angle beam types in the frequency range of 2 to 2.4

megahertz. Angle beam transducer angles of 70, 60,

and 45 degrees are to be used.

(2) A coupling material is needed to exclude air.

Typical coupling materials include water, oil,

grease, pastes, and glycerine. Generally, the

rougher the surface, the more viscous the coupling

agent required.

(3) Ultrasonic reference blocks are usually

needed to check the sensitivity and performance of

ultrasonic instrumentation and transducers for

inspecting critical welds. Most standards are manu-

factured with artificial defects in the form of drilled

holes with flat, round, or conical bottoms or slots

machined into the surface. AWS D1.1 recommends

several standards, the most common being the Inter-

national Institute of Welding (IIW) reference block

shown in figure 8-11.

Inspection procedures. The procedures

described conform to ASTM E 164 and AWS D1.1.

Ultrasonic inspection procedures are also outlined in

appendix U to the ASME Boiler and Pressure Vessel

Code, Section VIII, Division 1, and in Section V,

Article 5. In ultrasonic inspection, the most impor-

tant phase is the interpretation of indications. In

preparing for an ultrasonic inspection, an operator

must consider certain parameters: type and size of

transducer, couplant, scanning procedures, peaking

techniques, frequency, pulse length, linearity of

indications, distance/time relationship, and sensitiv-

ity/time relationship. Other parameters are speci-

men properties, such as material sound/velocity;

specific acoustic impedance; part geometry; mate-

rial attenuation; and noise level. Each signal peak

along the scan line represents a place in time where

the acoustic energy has encountered an interface or

a multiple of a previously generated signal. By

knowing the beam path and spread, the operator can

interpret the signal and separate relevant from irrel-

evant indications. The operator must consider

amplitude/distance response and amplitude/area

response when determining flaw size. The shape and

orientation of the flaw also affect the signal ampli-

tude. In attempting to determine flaw size, an opera-

tor must watch both the flaw signal amplitude and

the loss of amplitude of the back reflection.

(1) Before any inspection, the ultrasonic unit

must be calibrated for sensitivity and horizontal

sweep (distance); a calibration block or other recog-

nized method must be used.

(2) The surface of the weld area to be inspected

must be free of weld spatter (which will cause rapid

wear of the transducer), grease, dirt, oil, and loose

scale (which will cause scattering and attenuation).

Tight layers of paint need not be removed unless the

thickness exceeds 10 roils.

(3) A coupling agent must be used between the

search unit and the metal. The base metal is first

examined for lamella flaws using a straight beam

search unit, and then is inspected using the angle

8-18

TM 5-805-7

beam. Where possible, all welds should be scanned

from both sides on the beam face for longitudinal

and transverse discontinuities. The search unit must

be placed on the surface with the sound beam aimed

about 90 degrees to the weld and manipulated later-

ally and longitudinally so that the ultrasonic beam

passes through all of the weld metal.

(4) For welds not ground flush (fig 8-12), shear

wave is used in four different scans. For longitudinal

flaws, sound is directed into the weld from each

side. The transducer is oscillated to the left and right

with an included angle of about 30 degrees. To

detect transverse defects, the transducer is placed

on the base metal at the edge of the weld. It is then

positioned so that the sound beam makes about a 15-

degree angle to the longitudinal axis of the weld. To

scan, the search is moved along the weld edge from

both sides. For welds ground flush (fig 8-13), scan-

ning is done similarly. However, to detect longitudi-

nal flaws the transducer is moved across the weld.

And for transverse defects, the transducer is oscil-

lated left and right through a 30-degree angle while

continuously advancing along the top of the weld.

(5) When an indication of a flaw appears on the

CRT, the location and position of the transducer are

recorded. By using graphs, calculators, or guides,

the operator can accurately locate the position of

the defect in the weld. By using applicable charts

and attenuation factors, the weld discontinuity can

be accepted or rejected.

8-10. Destructive testing

In procedure qualification testing and welding

development work, metallographic specimens are

sometimes removed from a structure to check the

quality of the weldment. These tests are used to

determine visually the characteristics of the welds.

Metallographic test samples are sections cut through

the welds in any desired plane, then polished and

etched to reveal the structure. These specimens may

be examined with the naked eye or with various

magnifications,

including microscopic, Among the

characteristics that can be checked are the sound-

ness, location, and depth of penetration of the

welds; the metallurgical structures of the weld,

fusion zone, and heat affected zone; the extent and

distribution of undesirable inclusions in the weld;

hardness gradients; and the number of weld passes.

When metallographic specimens are removed from

any part of a structure, repairs must be made by

qualified welders or welding operators

using

accepted welding procedures. Peening or heat treat

ment may be required to develop the full strength of

a. Test methods. There are three categories of

destructive tests: chemical, hardness, and mechani-

cal tests.

(1) Chemical tests. Chemical tests are generally

used to validate the chemical composition or the

corrosion resistance of the base and weld metals.

Particular compositions of the metals involved, for

example, may be examined for conformance to

specifications. In addition, chemical analysis of the

weld metal can show whether welding produced the

expected results, or whether it introduced undesir-

able constituents into the weld metal. corrosion

tests demonstrate a weldment’s capability to with-

stand the corrosive environment to be encountered in

service. Because of the cost and time involved, a

weldment usually cannot be tested for corrosion

resistance by actual use under service conditions.

Therefore, accelerated corrosion tests that can be

conducted under laboratory conditions have been

developed.

(2) Hardness tests. Hardness tests measure the

resistance of materials to wear. For most metals,

ductility and corrosion resistance decrease as the

hardness increases. Since each operation during

welding has metallurgical effects, some specifica-

tions call for an upper limit to the acceptable hard-

ness of various areas of weld. Hardness testing is

done with equipment which, under a specific load,

forces a small hardened steel ball or diamond point

into the. surface of the metal. The depth of penetra-

tion is either measured directly by the machine, or

inferred from the dimensions of the impression. By

associating a number with each possible impression

depth, the inspector can develop a hardness scale.

This testing approach is used by the three most com-

mon hardness measuring devices: the Brinell,

Rockwell, and Vickers hardness testers. Hardness

numbers may vary from method to method because

of differences in the formulas used to define hard-

ness numbers, in the material type and shape used to

make the impression, and in the imposed load. How-

ever, tables of approximately equivalent hardness

numbers have been constructed.

(3) Mechanical tests. Mechanical tests (exclusive

of hardness) have been designed to test several weld

properties.

(a) Tensile tests are conducted on specimens

machined from a test weld and are used to measure

the strength of the weld joint. Specimens are usually

taken perpendicular to the weld, which is centered

in the specimen (fig 8-14). However, specimens are

sometimes taken along the weld and consist entirely

of weld metal. Specimens may have round or rectan-

gular cross sections, depending on the requirements

of the applicable welding code. The testing machine

TM 5-805-7

applies a tensile force until the specimen ruptures.

From readings on the machine and measurements of

the specimen before and after the test, properties

such as yield point or yield strength, ultimate

strength, and ductility are calculated. The primary

purpose of the test is to demonstrate that the weld

metal deposited by the selected procedures meets

or exceeds the minimum values specified in the

applicable code or specifications.

(b) Guided bend tests indicate a weld’s ductil-

ity. Test specimens are described as root-bend, face-

bend, or side-bend, depending on the surface

stretched in bending. Rectangular test specimens

similar to those prepared for tensile tests are

machined or ground to remove any weld reinforce-

ment. A test jig, such as that shown in figure 8-15, is

used to make the bend. with the plunger removed,

the specimen is placed across the shoulders of the

jig with the weld centered. The plunger is then

forced down until the specimen is bent into a U-

shape. The elongation of the tension surface is

determined by the relationship between the thick-

ness of the specimen and the radius of the die. The

specimen fails if it has cracks or other open defects

greater than a specified number and size, or if it

fractures.

specimens similar to those for guided bend tests.

Before the test, gage lines are inscribed across the

width of the sample of deposited weld metal. These

lines mark off a distance about 1/8 inch less than the

width of the weld. The sample is given an initial

bend (fig 8-1 6) by supporting the ends or shoulders

on rollers, then forcing the center down until the

specimen takes a permanent set. Next, a testing

machine or device (fig 8-16) is used to compress the

sample longitudinally until a crack or depression

appears on the convex face of the specimen, or until

the specimen is bent double. The load is removed

immediately if a defect appears before the specimen

is bent double. Percent elongation is calculated from

the initial and final distances between the gage

marks.

(d) Shear tests of fillet welds are conducted by

pulling specimens apart in a testing machine. The

dimensions of the specimens make it easy to use the

8-20

TM 5-805-7

FORCE

test results to obtain shear strength in pounds per

linear inch of weld. Figure 8-17 shows the shear test

specimen and indicates where to machine specimens

from test weldment.

(e) Nick-break tests are required in some

welding codes to detect weld defects. The nick-

break test specimens similar to a rectangular ten-

sile-test specimen, except that notches are cut at the

center of the weld. The specimen is then broken

either by pulling in tension or by bending. The spec-

imen is forced to break in the weld metal because of

the notches. After the specimen has been broken,

the fracture surfaces are examined for weld-metal

defects. If there are more than the minimum

allowed, the weld is rejected.

(f) Various types of impact tests are some-

times used to test the fracture toughness of the weld

metal when low-alloy, high-strength steels are being

welded. These tests measure the weld metal’s capa-

bility to resist crack propagation under low stress.

b. Sampling technique, Removal of samples by

sectioning is an accepted method of weld inspection

approved by various pressure-vessel codes. Because

the cavity must later be repaired by rewelding, the

method is sometimes considered a destructive test.

Samples may be taken for chemical analysis, etch

tests, subsize tension, or impact tests. The specific

method of removing samples depends on the size of

specimen needed; hole saws, bolt cutters, cold

chisels, or trepanning tools — a special power tool

with a hemispherical saw — are often used for sam-

ple removal. The samples must be carefully selected

to be representative of the weld or base metal being

checked.

8-21

TM 5-805-7

1 INITIAL SET

8-22

1/2”

TM 5-805-7

8-11. Leak testing

Leak tests are similar to proof tests for closed pres-

sure vessels; the container being tested is filled with

a fluid at a specified pressure. The choice of liquid

or gas depends on the purpose of the container and

the leakage that can be tolerated. For example, con-

tainers that are watertight may not be oiltight or

gastight. Leaks can be detected in several ways. For

oil or water, visual inspection of the outside of the

pressure vessel may suffice. Leaking air or gas can

be detected by the sound of the escaping gas, by use

of a soap film that forms bubbles as gas escapes

beneath it, or by immersion in a liquid in which the

escaping gas forms bubbles. For hydrostatic or gas

tests, a pressure gage attached to the vessel indicates

leaks by the drop in pressure after the tests begin.

Dyes introduced into liquids and tracers introduced

into gases can also indicate leakage. Weld defects

that cause leakage are not always detected by the

usual nondestructive testing methods. A tight crack

or fissure may not appear on a radiograph, yet will

form a leak path. A production operation, such as

forming or a proof test, may make leaks develop in

an otherwise acceptable weld joint. A leak test is

usually done on the completed vessel if all of the

weld joints can be inspected; at this stage there will

be no more fabricating operations after the inspec-

tion. Inspection is easier if the vessel is empty, The

most common types of leak testing are discussed

below.

a. The pressure-rise test method is used to see

whether any leaks exist. In this test, the part being

inspected is attached to a vacuum pump and evacu-

ated to a pressure of ().5 psi absolute. when this

pressure is reached, the connections to the vacuum

pump are sealed off, and the internal pressure of the

part is measured immediately. The pressure is mea-

sured again after at least 5 minutes (with the item

still sealed off from the vacuum pump). If the pres-

sure in the evacuated space remains essentially con-

stant, the welds are free of leaks. If there is a

pressure rise, at least one leak is present, and the

helium-leak test described in b below must be used,

b. The helium-leak test is more precise than the

pressure-rise method and is used to find the exact

location of these leaks. Helium-leak testing is slow,

however, so it normally is not used to inspect large

items unless a leak definitely exists. This inspection

method requires the use of a helium mass spectrom-

eter to detect the presence of helium gas. The mass

spectrometer is connected to the pumping system

between the vacuum pump and the item being

inspected. Then the item is evacuated by a vacuum

pump to a pressure of less than 50 microns of mer-

cury. The mass spectrometer can detect helium in

the evacuated

directed at the

atmosphere. If

space. A small jet of helium gas is

side of the weld joint exposed to the

there is a leak, some of the helium is

sucked through it into the evacuated space, and the

mass spectrometer immediately indicates the pres-

ence of helium. Of course, if no leak is present, no

helium will enter the evacuated space and no indica-

tion will appear on the mass spectrometer. To deter-

mine the exact location of leaks, the jet of helium is

moved along the surface of the weld joint. At the

same time, an inspector carefully watches the mass

spectrometer. If there is an indication, the leak is at

the point where the helium jet is hitting the surface

of the weld joint.

c. To detect leaks, the ultrasonic translator detec-

tor uses the ultrasonic sounds of gas molecules

escaping from a vessel under pressure or vacuum.

The sound created is in the frequency range of

35,000 and 45,000 Hertz, which is above the range

of human hearing and is therefore classified as

ultrasonic. Certain characteristics of these frequen-

cies are useful for detections. They are outside the

range of most plant and machine noise, and the short

wave length of these frequencies permits the use of

highly directional microphones. Any system or ves-

sel that can be pressurized or evacuated to a pres-

sure of 3 psi can be inspected. The operator simply

listens to the translated ultrasonic sounds while

moving a hand-held probe along the weld (in the

same way that a flashlight. is used to illuminate the

suspected leak locations). The detectors are simple

to operate and require minimum operator training.

d. Some of the following tests — particularly the

air-soap solution test — can be conducted on a ves-

sel during or after assembly. The inspector can

locate large defects in order to reduce the time

needed for final leak testing. After testing, vessels

should be thoroughly cleaned to remove all traces of

soap solution.

(1) Hydrostatic test. This test should conform to

the applicable requirements of a particular vessel or

system. only distilled or deionized (demineralized)

water having a pH of 6 to 8 and an impurity content

not greater than 5 ppm is used. Traces of water

should be removed from the inside before final leak

testing is begun.

(2) Water submersion test. In this test, the ves-

sel is completely submerged in clean water. The

interior is pressurized with gas, but the design pres-

sure must not be exceeded. The size and number of

any gas bubbles indicates the size of leaks,

(3) Soap solution test, In this test, the vessel is

subjected to an internal gas pressure not exceeding

the design pressure. A soap or equivalent solution is

8-24

applied so that connections and welded joints can be

examined for leaks.

(4) Air-ammonia test. This test involves intro-

ducing air into the vessel until so percent of the

design pressure is needed. Anhydrous ammonia is

then introduced into the vessel until 55 percent of

the design pressure is reached; air is then reintro-

duced until the design pressure is reached. Each

joint is carefully examined by using as a probe either

a swab wetted with 10N solution of muriatic acid

(HCL), a sulphur candle, or sulphur dioxide. A wisp

of white smoke indicates a leak.

(5) Halide torch test. In this test, the vessel is

pressurized to a value not exceeding the design

pressure; a mixture of SO percent Freon and carbon

dioxide or 50 percent Freon and nitrogen is used.

Each joint is carefully probed with a halide torch to

detect leaks, which are indicated by a change in the

color of the flame.

(6) Halogen snifter test. A Freon inert gas mix-

ture is introduced into the vessel until the design

pressure is reached. About 1 ounce of Freon for

every 30 cubic feet of vessel volume is required.

The inspector passes the probe of a halogen vapor

analyzer over the area to be explored. This probe is

held about 1/2 inch from the surface being tested

and is moved at about 1/2 inch per second. Since the

instrument is responsive to cigarette smoke and

vapor from newly dry-cleaned clothing, the air

should be kept clean where the test is being done. In

addition, the test should be done in a substantially

draft-free enclosure.

8-25

CHAPTER 9

SAFETY

9-1. General

The safety of the welding operators, foreman, and

inspectors at the construction job site is a primary

consideration. All precautions must be taken to

ensure the safe completion of the construction proj-

ect. The Occupational Safety and Health Adminis-

tration (OSHA) of the U.S. Department of Labor has

issued Health and Safety Standards covering such

topics as radiation protection, welding, cutting and

heating, use of ladders and scaffolds, steel erection,

and hearing and head protection. Most of the stan-

dards for welding are in Code of Federal Regula-

tions, Title 29, Chapter XVII, Part 1910.

9-2. Hazards

a. Welding and cutting. When welding and cutting

is being done, three major safety hazards must be

considered and adequate precautions taken. First,

the eyes and exposed skin must be protected from

the intense light radiation and the heat of the weld-

ing arc and flames. Second, welding, cutting, and

grinding operations must be prevented from causing

fires. Third, care must be taken in handling, weld-

ing, and cutting containers that have held combusti-

ble or toxic materials. Cutting or welding also must

be done carefully if materials in the fluxes, coatings,

and base metals produce explosive or toxic fumes

when heated. There are other safety considerations

for welding and cutting operations; all personnel

involved should be familiar with the requirements of

the OSHA safety standards. The AWS also publishes

and distributes information on safe welding and cut-

ting practices.

b. Radiographic inspection. Radiographic inspec-

tion involves ionizing radiation. Individuals can be

protected from this radiation primarily by shielding

and distance. For information on safe procedures

and practices for radiography, refer to Title 10,

Code of Federal Regulations; the American Society

for Non-Destructive Testing; and AWS.

c. Noise levels. Hearing loss, either partial or

total, is a direct result of working without proper ear

protection at steel construction sites. Contractors

must conform to OSHA standards for permissible

noise levels and time durations.

d. Air quality. Welding and cutting operations

increase dust and ozone levels near the construc-

tion. Welding galvanized steel also releases zinc

oxide, which can be very hazardous to welding oper-

ators and their assistants. Therefore, proper ventila-

tion should be provided for all personnel at the

welding site. Particular attention should be paid to

safety when personnel are welding inside large

tanks. There should always be ventilation for such an

operation.

9-1

TM 5-805-7

APPENDIX A

REFERENCES

‘----

Government Publications

Department of Defense.

MIL-C-15726E Copper-Nickel Alloy, Rod, Flat Products (Flat Wire, Strip, Sheet, Bar and Plate),

and Forgings.

MIL-E-22200F General Specification for Electrodes, Welding Covers.

MIL-E-18193 Electrode, Welding, Carbon Steel and Alloy Steel, Bare, Coiled.

MIL-E-19822A Electrodes, Welding, Bare, High-Yield Steel.

MIL-E-23765/lD Electrodes and Rods-Welding, Bare, Solid, Mild and Alloy Steel.

MIL-E-23765/2B Electrode and Rod-Welding, Bare, Solid, Low Alloy Steel.

MIL-I-6868 Inspection Process, Magnetic Particle.

MIL-R-11468 Radiographic Inspection, Soundness Requirements for Arc and Gas Welds in Steel,

MIL-R-11470 Radiographic Inspection, Qualification of Equipment, Operators and Procedures.

MIL-R-45774(2) Radiographic Inspection, Soundness Requirements for Fusion Welds in Aluminum

and Magnesium Missile Components.

MIL-STD-00453B Radiographic Inspection.

MIL-STD-271E Nondestructive Testing Requirement for Metals.

MIL-STD-410D Nondestructive Testing Personnel Qualification and Certification (Eddy Current,

Liquid Penetrant, Magnetic Particle, Radiographic and Ultrasonic).

MIL-STD-779 Reference Radiographic for Steel Fusion Welds, Vol. I, Vol. II, Vol. III.

Department of the Army.

TM 9-237 Welding Theory and Application.

Nuclear Regulatory Commission.

1717 H St., NW, Washington, D.C. 20555

General Services Administration (GSA).

18th and F Streets, NW, Washington, D.C. 20405 Code of Federal Regulations, Title 10, Chapter I, Parts

20 and 34, and Title 29, Chapter XVII, Part 1910, published by the Office of the Federal Register,

National Archives and Records Service (Updated Annually)

Occupational Safety and Health Administration (OSHA),

Bureau of National Affairs, 1231 25th St., NW, Washington, D.C. 20037

Nongovernment Publications

Aerospace Materials Specification (AMS), Society of Automotive Engineers, 400 Commonwealth Drive,

Warrendale, PA 15096

AMS 2635B Radiographic Inspection (updated periodically).

AMS 2640H Magnetic Particle Inspection (updated periodically).

AMS 2645G Fluorescent Penetrant Inspection (updated periodically).

AMS 2646B Contrast Dye Penetrant Inspection (updated periodically).

American Institute of Steel Construction (AISC), 400 N. Michigan Ave., 8th Floor, Chicago, IL 60611

Manual of Steel Construction

Aluminum Association, inc. (AA), 818 Connecticut Avenue, NW Washington, DC 20006

American Concrete Institute (ACI), P.O. Box 19150, Detroit, MI 48219

ACI 318-77 Building Code Requirements for Reinforced Concrete.

American Iron and Steel Institute (AISI), 1000 16th Street, NW, Washington, DC 20036

Industry Practices for Ultrasonic Nondestructive Testing of Steel Tubular Products.

Ultrasonic Inspection of Steel Products.

American National Standards institute (ANSI,, 1430 Broadway, New York, NY 10018

ANSI B31.1-80 Power Piping.

A-1

TM 5-805-7

American Petroleum Institute (API), 1801 K Street, Washington, DC 20006

API-STD-1104 API Specification for Field Welding of Pipelines.

American Society for Metals (ASM), Metals park, OH 44073

Metals Handbook, ASM Handbook Committee, Volume 6: Welding and Brazing (9th

Ed., 1983).

American Society for Nondestructive Testing (ASNT), 3200 Riverside Drive, Columbus, OH 43221

ASNT-TC-lA Recommended Practice Nondestructive Testing Personnel Qualification and

Certification (updated periodically).

Nondestructive Testing Handbook, Vols. I and II, Robert McMaster, cd., The Ronald

Press Co.

American Society for Testing and Materials (ASTM), 1916 Race Street, Philadelphia, PA 19103

ASTM A514-82

ASTM A517/

A517M-82

ASTM A36-81

ASTM A242-81

ASTM A441-81

ASTM A572-82

ASTM A53-82

ASTM A106-82

ASTM A139-74

ASTM A691-81

ASTM A203-81

ASTM A588-81

ASTM A134-80

ASTM A671-80

ASTM A672-81

ASTM A710-79

ASTM E390-75

ASTM E709-80

ASTM E94-77

ASTM E138-81

ASTM E142-77

ASTM E164-81

ASTM E165-80

Specification for High-Yield Strength, Quenched and-Tempered Alloy Steel Plate,

Suitable for Welding. (Rev. A)

Specification for Pressure Vessel Alloy Steel, High-Strength, Quenched and Tem-

pered.

Specification for Structural Steel. (Rev. A)

Specification for High-Strength Low-Alloy Structural Steel.

Specification for High-Strength Low-Alloy Structural Manganese Vanadium Steel.

Specification for High-Strength Low-Alloy Columbium-Vanadium Steels of

Structural Quality.

Specification for Pipe, Steel, Black and Hot-Dipped Zinc-Coated Welded and

Seamless.

Specification for Seamless Carbon Steel Pipe for High-Temperature Service.

Specification for Electric-Fusion (Arc) -Welded Steel Pipe (Sizes 4 in. and over) (R

1980).

Specification for Carbon and Alloy Steel Pipe, Electric-Fusion-Welded for High-

Pressure Services at High Temperatures.

Specification for Pressure Vessel Plates Alloy Steel, Nickel.

Specification for High-Strength Low-Alloy Structural Steel with 50,000 psi

Minimum Yield Point to 4 in. Thick.

Specification for Pipe, Steel, Electric-Fusion (Arc) -Welded (Sizes NPS16 and over).

Specification for Electric-Fusion-Welded Steel Pipe for Atmospheric and Lower

Temperatures.

Specification for Electric-Fusion-Welded Steel Pipe for High-Pressure Service at

Moderate Temperatures.

Specification for Low Carbon Age-Hardening Nickel-Copper-Chromium-

Molybdenum-Columbium and Nickel-Copper-Columbium Alloy Steels.

Radiographs for Steel Fusion Welds.

Practice for Magnetic Particle Examination.

Radiographic Testing, Standard for Recommended Practice.

Standard Method for Wet Magnetic Particle Inspection.

Standard Method for Controlling Quality of Radiographic Testing.

Standard Recommended Practice for Ultrasonic Contact Examination of Weldments.

Standard Recommended Practice for Liquid Penetrant Inspection Method.

American Society of Mechanical Engineers (ASME), United Engineering Center, 345 East Forty-Seventh

Street, New York, NY 10017

Boiler and Pressure Vessel Code (1974). Section II, Material Specification. Section

III, Nuclear Power Plant Components.

Section V, Nondestructive Examination. Section VIII, Pressure Vessels. Section IX,

Welding Qualification.

American Welding Society (AWS), P.O. Box 351040,550 LeJeune Road, Miami, FL 33135

AWS A3.0-80 Welding Terms and Definitions Including Terms for Brazing, Soldering, Thermal

Spraying, and Thermal Cutting.

AWS A5.1-81 Specifications for Carbon Steel Covered Arc Welding Electrodes.

TM 5-805-7

AWS A5.4-81

-AWS A5.5-81

AWS A5.9-81

AWS A5.14-76

AWS A5.17-80

AWS A5.18-79

AWS A5.20-79

AWS A5.22-80

AWS A5.23-80

AWS D1.1-83

AWS A5.11-76

AWS A5.10-80

AWS D12.1-75

AWS D19.0-72

Specification for Corrosion-Resisting Chromium and Chromium-Nickel Steel

Covered Electrodes.

Specification for Low-Alloy Steel Covered Arc-Welding Electrodes.

Specification for Corrosion-Resisting and Chromium-Nickel Steel Bare and

Composite Metal Cored and Stranded Arc Welding Electrodes and Welding Rods.

Specification for Nickel and Nickel Alloy Bare Welding Rods and Electrodes.

Specification for Bare Carbon Steel Electrodes and Fluxes for Submerged Arc

Welding.

Specification for Carbon Steel Filler Metals Gas Shielded Arc Welding.

Specification for Carbon Steel Electrodes for Flux Cored Arc Welding.

Specification for Flux-Cored Corrosion-Resisting Chromium and Chromium-Nickel

Steel Electrodes.

Specification for Bare Low-Alloy Steel Electrodes and Fluxes for Submerged Arc

Welding.

Structural Welding Code—Steel.

Specifications for Nickel and Nickel Alloy Covered Welding Electrodes.

Specification for Aluminum and Aluminum Alloy Bare Welding Rods and Electrodes.

Reinforcing Steel Welding Codes. (superseded by AWS D1.4-79)

Welding Zinc-Coated Material (superseded by AWS C2.2)

American Welding Society (AWS), P. O. Box 351040,550 LeJeune Road, Miami, FL 33135

Welding Handbook

Volume 1, Fundamentals of Welding, 6th Edition (1968)

Volume 2, Welding Processes, 7th Edition (1978)

Volume 3, Welding Processes, 7th Edition (1980)

Volume 4, Metals and Their Weldability, 6th Edition (1968)

Volume 5, Application of Welding, 6th Edition (1968)

Welding Research Council, 345 E. 47th Street, New York, NY 10017

Weldability of Steels, Robert D. Stout and W. D’Orville Doty, 1971

TM 5-805-7

APPENDIX B

QUALIFICATION TESTING

B-1. General

A project manager must determine the ability of a

manufacturer, contractor, fabricator, or erector to

produce quality welds consistently. Qualification

requirements insure that properly trained welding

personnel use approved procedures and adequate

equipment. The qualification requirement includes

a wide range of materials, procedures, processes,

equipment, and personnel. For a construction proj-

ect, a weld quality assurance program uses qualifica-

tion testing for the welding procedure and the

welding personnel.

B-2. Procedure qualification

a. Purpose. The purpose of the procedure qualifi-

cation test is to demonstrate that certain procedures

produce welds of suitable mechanical properties and

soundness.

b. Method. Small test plates with the same chemi-

cal composition as the production weldments are

welded with the proposed production procedure.

The joint geometry, welding process, welding

parameters, filler metals, shielding materials, and

welding position used to make the test plates are

also the same as or equivalent to those for the actual

production weldment. The plates are then tested to

see whether the weld’s soundness and mechanical

properties meet the acceptance standards of the

production weld. The requirements for qualifying a

welding procedure are governed by the codes con-

cerning the weld’s specific application.

c. Testing.

(1) The procedure qualification plates are usu-

ally tested nondestructively, with the same tests

required for the production weld. The plate must

meet the nondestructive test acceptance standards

of the code applicable to the weld’s specified use,

(2) Tensile and bend tests are normally used for

procedure qualification plates. Some welds also

require the nick-break test, impact tests, and metal-

lographic examination.

(3) Tensile test specimens are removed so that

the long axis of the specimen is transverse to the

welding direction and is centered on the weld’s cen-

terline. The actual specimen geometry varies widely

to meet requirements of various welding codes. The

specimens may be round or flat and may have a

reduced section; the flat specimen may have the

weld reinforcement removed. To be acceptable, the

tensile specimens must exceed the minimum

requirements in the welding code for the type of

material being used. The primary purpose of the

tensile test is to demonstrate that the weld metal

deposited by the selected procedure is strong

enough to meet the design requirements.

(4) Three types of bend tests are used for proce-

dure qualification. Root-bend and face-bend tests

are used on materials up to 3/8-inch thick. Side-

bend tests are used for thicker materials. The names

of these procedures refer to the surface that is

stretched in tension during bending. In the root-

bend test, the root of the weld is placed in tension.

In the face-bend and side-bend tests, the weld

crown and a transverse cross section, respectively,

are put in tension during bending. The specimens

are machined or ground to remove the weld rein-

forcement and then bent around a die of specified

radius. The amount of elongation of the tension sur-

face is usually about 20 percent. The bend test indi-

cates the ductility of the weld metal and detects the

small defects in the weld that tend to open up and

become readily visible. The acceptance criterion for

bend tests is that no fissures exceeding a specified

length (usually 1/8 inch) be present on the tension

surface after bending.

(5) Some welding codes require nick-break tests

to detect weld defects. The nick-break test specimen

is similar to a rectangular tensile-test specimen,

except that notches are cut at the center of the weld.

The specimen is then broken either by pulling it in

tension or by bending it. The notches cause the

specimen to break in the weld metal. After this, the

fracture surfaces are examined for weld metal

defects. If there are too many defects, the weld is

rejected.

(6) Various types of impact tests are sometimes

used to test the fracture toughness of the weld metal

when low-alloy, high-strength steels are being

welded. These tests are designed to measure the

capability of the weld metal to resist crack propaga-

tion under low-stress conditions.

(7) Metallographic examination involves polish-

ing, etching, and examining weld sections under low

magnification to detect porosity, cracks, or other

defects in the weld metal. This test maybe required

for certain applications, particularly when the weld

TM 5-805-7

configuration does not allow meaningful test results

to be obtained by the mechanical property test

methods discussed above.

d. Usefulness of procedure qualification. The pro-

cedure qualification test is useful for demonstrating

the quality and properties of the weld before its

production. Since it is almost impossible to duplicate

actual production welding conditions, this test is

conducted under simulated conditions. In an actual

welding situation, conditions arise that could not

have been anticipated when the procedure was

being qualified (e.g., abrupt weather changes).

Therefore, the production phase must be closely

supervised so that such conditions are noticed as

they occur. If these factors can alter the quality of

the weld, they should be evaluated.

B-3. Welder and welding operator

qualification

a. General. Weld quality is determined by the spe-

cific welding procedure and by the ability of the

welder or welding operator to apply that procedure.

Welder qualification tests determine the operator’s

ability to produce sound welds that conform to the

procedure specification. The tests indicate whether

the welder or welding operator can produce accept-

able welds, but do not indicate whether he/she will

produce acceptable welds during actual production.

Consequently, during the construction process, the

welds must be inspected before and after

completion.

b. Method. In personnel qualification testing, the

welder or welding operator is required to weld a

small test plate in a material which is the same as or

similar to that of the actual production weldment.

The qualified procedure for that weldment must be

used. The qualification plate is then nondestruc-

tively examined and destructively tested. These

steps insure that the weld soundness meets the mini-

mum acceptance standards of the welding code gov-

erning the particular application.

c. Testing. Testing methods used for personnel

qualification tests usually include the nondestructive

examinations applicable to the specific job and any

combination of the bend tests described previously.

In some instances, nick-break tests may also be

required because they examine weld soundness

rather than weld metal properties. Tensile tests are

usually not required for examining personnel

qualifications.

d. Usefulness of personnel qualifications. The per-

sonnel qualification tests assure a customer that the

welders have been screened and are capable of pro-

ducing welds that conform to procedure and specifi-

cation requirements. These tests do not guarantee

that the welder will produce satisfactory welds each

time, but do tend to eliminate welders whose work

is never acceptable. As with procedure qualifica-

tions, the value of personnel qualifications increases

when the production welding conditions are simu-

lated as closely as possible.

TM 5-805-7

BIBLIOGRAPHY

Uoe7240 Welding Technical Manual TM 5 805 7

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