Arc Welding Processes Handbook E-Book

Ramesh Singh

• Herausgeber: John Wiley & Sons
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 735

Veröffentlichungsjahr: 2021

Beschreibung

ARC WELDING PROCESSES HANDBOOK An applied reference, each part of this Handbook gives valuable information regarding the industry or industries where the process is commonly used as well as a description of the equipment. Written by a welding/metallurgical engineer with over 40 years of experience, Arc Welding Processes Handbook delivers the welding and materials expertise required to master complex welding processes and techniques to ensure that the task is done correctly and safely, while reinforcing an understanding of international welding standards and rules. The perfect handbook for those professionals who need an up-to-date reference to advance processes as well as those welders new to the field and need to hone their skills. Arc Welding Processes Handbook five-part treatment starts with a clear and rigorous exposition of the applications and equipment of Shielded Metal Arc Welding (SMAW) and Gas Tungsten Arc Welding (GTAW), followed by self-contained parts concerning processes applications and equipment for Gas Metal Arc Welding (GMAW), Flux Core Arc Welding (FCAW), and Submerged Arc welding (SAW). An applied reference, each Part of Arc Welding Processes Handbook offers valuable information regarding the industry or industries where the process is commonly used as well as a description of the equipment. In addition, this Handbook discusses the challenges presented by a number of corrosion-resistant alloys (CRAs). Case studies are included throughout the reference to reinforce an understanding of how these processes were applied in the field and how they intersect with issues that may arise with equipment use and materials. The reader will also find in the Handbook: * Highlights the key advantages and limitations of each process and suggests an alternate approach to overcome those limitations * One-of-a-kind case studies to reinforce an understanding of international welding standards and rules. * Quality of welds, type of equipment, materials, and inspection and testing for each process. * Metal joining processes like soldering and brazing. Audience The intended market for this book is professionals working in shipbuilding, construction of buildings, bridges, and other structures and to join pipes in pipelines, power plants, manufacturing, and repair.

Leseprobe

Table of Contents

Cover

Title Page

Copyright

List of Figures

List of Tables

Foreword

Preface

1 Introduction to Welding Processes

1.1 Synopsis

1.2 Keywords

1.3 Welding

1.4 Defining Welding

1.5 Welding and Joining Processes

1.6 Arc Welding

1.7 Efficiency of Energy Use

1.8 Welding Procedures

1.9 Qualification of Welders and Operators

2 Shielded Metal Arc Welding (SMAW)

2.1 Synopsis

2.2 Keywords

2.3 Introduction

2.4 Process Fundamentals

2.5 How the Process Works

2.6 Power Sources

2.7 AC Power Sources

2.8 Direct Current Power Sources

2.9 Welding Safety and Personal Protecting Equipment

2.10 Covered Electrodes Used in SMAW Process

2.11 Welding Training – Making of a Welder

2.12 Welding Other Metals

2.13 Welding and Fabrication of Duplex Stainless Steels

2.14 SMAW Welding Nickel Alloys

2.15 Minimizing Discontinuities in Nickel and Alloys Welds

2.16 Review Your Knowledge

3 Gas Tungsten Arc Welding

3.1 Synopsis

3.2 Keywords

3.3 Introduction to Gas Tungsten Arc Welding Process

3.4 Process Description

3.5 How the Process Works

3.6 Process Advantages and Limitations

3.7 Power Sources

3.8 Shielding Gases

3.9 Gas Regulators and Flowmeters

3.10 GTAW Torches, Nozzles, Collets, and Gas Lenses

3.11 Tungsten Electrodes

3.12 Joint Design

3.13 Power Source Remote Control

3.14 Installation of Welding Machines

3.15 Power Source Cooling System

3.16 Welding Connections – Welding Cable and Welding Torch Connections

3.17 Welding Power Source Classification by NEMA

3.18 Welding Personal Protecting Equipment

3.19 Other Essential Clothing for Welders

3.20 Filler Wires Used in GTAW Process

3.21 Classification and Identification of Welding Wires

3.22 The Aluminum Alloy Temper and Designation System

3.23 Welding Metals Other Than Carbon and Alloy Steels

3.24 GTAW Welding of Aluminum

3.25 GTAW Welding of Stainless Steel

3.26 Mechanical Properties

3.27 Welding Nickel Alloys

3.28 Later Developments in GTAW Process

3.29 Plasma Arc Welding

3.30 Review Your Knowledge

4 Gas Metal Arc Welding

4.1 Synopsis

4.2 Keywords

4.3 Introduction to Gas Metal Arc Welding Process

4.4 Process Description

4.5 Components of the Welding Arc

4.6 Effects of Variables on Welding

4.7 Advanced Welding Processes for GMAW

4.8 The Adaptive Loop

4.9 Advanced Waveform Control Technology

4.10 Equipment for GMAW Process

4.11 GMAW Power Sources

4.12 Installation of Welding Machines

4.13 Welding Various Metals

4.14 Welding Nickel Alloys

4.15 Minimizing Discontinuities in Nickel and Alloys Welds

4.16 Calculating Heat Input in Pulsed Arc GMAW

4.17 Review Your Knowledge

5 Flux Cored Arc Welding (FCAW) Process

5.1 Synopsis

5.2 Keywords

5.3 Introduction to Flux Cored Arc Welding (FCAW) Process

5.4 Process Description

5.5 Welding Wires/Electrodes

5.6 Power Sources

5.7 Other Accessories to Power Source

5.8 Shielding Gases

5.9 Welding Various Metals

5.10 Tips for Good Welding by FCAW Process

5.11 Test Your Knowledge

6 Submerged Arc Welding (SAW)

6.1 Synopsis

6.2 Keywords

6.3 Introduction to Submerged Arc Welding (SAW) Process

6.4 Operating Characteristics

6.5 Submerged Arc Welding (SAW) Process

6.6 How the SAW Process Works

6.7 SAW Process Variants

6.8 SAW Power Source and Equipment

6.9 Welding Heads (Gun)

6.10 Fluxes

6.11 Submerged Arc Welding Various Metals

6.12 Test Your Knowledge

7 Useful Data and Information Related to Welding and Fabrication

7.1 Common Weld Symbols and Their Meanings

7.2 Fillet Welds

7.3 Groove Welds

7.4 Pipe Schedule

7.5 Terms and Abbreviations

7.6 Procedure Qualification Range as Per the Material Group

7.7 Material Qualification Rage for Procedure Qualification Based on P-Numbers

7.8 Temperature Conversion

7.9 Useful Calculations

7.10 Effect of Temperature on Gas Cylinder Pressure

Index

End User License Agreement

List of Illustrations

Chapter 1

Figure 1.1 General lay out of welding and joining processes.

Chapter 2

Figure 2.3 A SMAW welder welding on a pipeline project.

Figure 2.4 Typical SMAW setup.

Figure 2.5 Welding arc action and various components of welding.

Figure 2.6 Above (2 graphs), graph 1 above, shows the volt-ampere curve, (output...

Figure 2.7 The schematic above shows the key components of an AC transformer.

Figure 2.7.3 Schematic of a movable shunt type transformer control.

Figure 2.7.4 A schematic of a movable coil reactor, the position of the reactor ...

Figure 2.7.5 A magnetic amplifier transformer output control, the diode allows t...

Figure 2.7.6 The top portion of the figure shows the use of diodes – shown in Re...

Figure 2.7.7 A schematic drawing of single-phase DC power source with SCR bridge...

Figure 2.8.1 Shows the schematic of single phase bridge type rectifier.

Figure 2.8.2 Three phase bridge-type rectifier.

Figure 2.8.1.1 Schematic diagram of a DC generator.

Figure 2.8.1.2 Circuitry of an exciter system.

Figure 2.8.3 Current conversion and resulting wave forms.

Figure 2.8.3.1 Copper and aluminum welding leads: note the number of fine wires ...

Figure 2.8.3.2 Different types of SMAW electrode holders.

Figure 2.8.4.1 Various types of cable connectors, and ground clamp. Pictures cou...

Figure 2.8.5.1 NEMA rating.

Figure 2.9.1 A typical hand-held welding shield.

Figure 2.9.2 Miller Digital Elite helmet.

Figure 2.9.3 A typical welding helmet.

Figure 2.10.2 Portfolio of SMAW electrodes.

Figure 2.10.3 AWS electrode classification method.

Figure 2.10.5.1 Shop use electrode drying oven.

Figure 2.10.5.2 Portable electrode holder also called quivers.

Figure 2.11.1 Different types of weld joints.

Figure 2.11.2 Different types of weld designs.

Figure 2.11.3 Welding positions for welding a plate, the positions are primarily...

Figure 2.11.4 Positions of plate and pipe butt welds and fillet welds with both ...

Figure 2.11.5 Above figure shows the permitted angular tolerance for specificall...

Figure 2.11.3.1 Testing a fillet weld.

Figure 2.11.3.2 Testing a fillet weld using a hammer.

Figure 2.11.3.3 Size and nomenclature of fillet weld.

Figure 2.11.3.4 A single pass fillet weld.

Figure 2.11.3.5 A single pass fillet weld with (arc termination) stop in the mid...

Figure 2.11.3.6 A multi-passes fillet weld-note the termination of arc start and...

Figure 2.11.3.7 A micro-etch of a double sided two pass fillet weld – compare th...

Figure 2.11.4.1 Weld appearances matched with arc current, and arc travel speed.

Figure 2.11.4.2 Pictures of the weld appearances and probable cause for the qual...

Figure 2.11.5.1 Offsetting the weld setup for distortion control.

Figure 2.11.9 This is a rotator with one end of the pipe held in a three-jaw, se...

Figure 2.11.10 This rotator is similar to the one above except that the pipe end...

Figure 2.11.11 A heavy-duty rotator.

Figure 2.11.12 Weld tacks bridging two pieces of pipe.

Figure 2.11.13 Shows a removable tack.

Figure 2.11.14 This picture shows both the bridge tack using external pieces of ...

Figure 2.11.15 Typical CS pipe weld.

Figure 2.11.10.1 Bevel edge preparation for vertical-up pipe in 6G position.

Figure 2.11.10.2 The vertical up progression - note the direction of electrode m...

Figure 2.11.11.1 Vertical down progression.

Figure 2.11.11.2 Weld profile of each pass.

Figure 2.11.11.3 The sketch above shows a typical weld layers of several passes ...

Figure 2.12.6 Aluminum fillet weld-bend testing.

Figure 2.12.12 Typical stainless-steel pipe weld, and weld-o-let on the header.

Figure 2.12.13 Pipe is assembled and prior to welding, the welder is tacking the...

Figure 2.12.18 Schaeffler diagram.

Figure 2.12.19 DeLong diagram.

Figure 2.14 Nickel alloy plate being welded.

Figure 2.14.1 Nickel is in 10th group and 4th period in the periodic table, its ...

Figure 2.14.2 Typical nickel welding electrodes – note the electrode identificat...

Figure 2.14.3 Nickel alloy welding (note the fillet weld in upward progression).

Chapter 3

Figure 3.3.1 Typical GTAW welding.

Figure 3.3.2 A GTAW welder, note the welding torch, and the filler wire in each ...

Figure 3.4.1 Typical GTAW welding process with details of the welding torch.

Figure 3.5.1 A typical GTAW set-up with positions of gas cylinder, welding machi...

Figure 3.5.2 The cleaning process by the current cycle.

Figure 3.5.3 High and low frequency currents in pulsing.

Figure 3.6.1 DC HF output circuit.

Figure 3.7.1 The graph.

Figure 3.7.2 Four AC wave forms.

Figure 3.7.2.2 Effect of Independent AC amperage control on weld penetration and...

Figure 3.7.2.3 Effect of variation in AC frequency on the weld profile and penet...

Figure 3.7.2.4 Provides an example of a weld done at 150 Hz and 40 Hz.

Figure 3.7.2.5 Weld profile as a result of extended EN of the cycle.

Figure 3.7.2.6 Weld profile as a result of reduced EN cycle.

Figure 3.7.4.1 A schematic drawing of single-phase DC power source with SCR brid...

Figure 3.7.6.1 Schematic diagram of a DC generator.

Figure 3.7.6.2 DC excitation circuit.

Figure 3.9.1 Gas flow meters (A) shows the tube type flow meter, and the bottom ...

Figure 3.10.1 A typical manual welding torch, note the water cooling, gas supply...

Figure 3.10.2 Various nozzles types and sizes.

Figure 3.10.3 A gas lens, with mesh, and holding circlip.

Figure 3.10.4 An assortment of manual welding GTAW torch components.

Figure 3.11.1 Electrode tips.

Figure 3.11.2.1 The tip angle 60°, note the depth of the deeper penetration and ...

Figure 3.11.2.2 The tip angle 30°, note the depth of the shallower penetration a...

Figure 3.11.2.3 The tip angle 15°, note the depth of the shallowest penetration ...

Figure 3.12.1 Five basic weld designs (Courtesy of Indian Air force training man...

Figure 3.16.1 Copper and Aluminum welding leads: note the number of fine wires t...

Figure 3.25.9.3.1 Welder is tacking a pipe prior to welding.

Figure 3.25.9.3.2 A nozzle is welded on a pipe header.

Figure 3.25.10.2.1 Schaeffler diagram.

Figure 3.25.10.2 DeLong diagram.

Figure 3.16.2 Various types of cable connectors, and ground clamp. Pictures Cour...

Chapter 4

Figure 4.3.1 Typical GMAW welding.

Figure 4.4.1 A GMAW operator welding on an offshore pipeline.

Figure 4.4.1.1 Short circuit transfer (arc-action and cycle).

Figure 4.4.1.2 Current voltage range for various transfer mode.

Figure 4.11.1 Typical GMAW (MIG) welding set up with the external wire feed unit...

Figure 4.12.1 A typical GMAW torch with trigger type on-off switch on the handle...

Figure 4.12.2 Blow out of the GMAW torch that shows some of the components that ...

Figure 4.12.3 The GMAW torch and the cable connector.

Figure 4.12.1.4 Copper and aluminum welding leads: note the number of fine wires...

Figure 4.13.8.1 (a) Contour of a weld bead in the flat position with the work ho...

Figure 4.13.12.1 WRC diagram.

Chapter 5

Figure 5.3.1 FCAW-S self-shielding tubular wire process.

Figure 5.3.2 FCAW-G, gas shielding solid wire process.

Figure 5.4.1 Typical FCAW setup.

Figure 5.5.1 FCAW electrode classification system.

Figure 5.8.7.2.1 Shows the metal transfer through the arc with CO

2

shielding on ...

Chapter 6

Figure 6.3.1 Schematic display of the SAW process.

Figure 6.3.2 Shows the submerged arc welding of a plate.

Figure 6.3.3 Shows the SAW of a pipe in a fabrication shop – note the arc and fl...

Figure 6.3.4 Shows the completed pipe weld.

Figure 6.3.5 Higher deposition rate of SAW process.

Figure 6.6.1 Showing SAW process in progress on a pipe weld.

Figure 6.6.2 Shows the collected flus for cleaning and reusing.

Figure 6.7.1 Multi-wire SAW system.

Figure 6.7.3 Tandem head strip wire SAW process for cladding.

Chapter 7

Figure 7.1 Structure of the welding symbol.

Figure 7.2 Welding symbol arrows.

Figure 7.3 Welding symbol position of the arrows.

Figure 7.4 Significance of the circle on the arrows.

Figure 7.5 Symbols for type of welds.

Figure 7.6 Symbol of fillet weld.

Figure 7.7 Shows the side of the metal where the fillet weld is required to be m...

Figure 7.8 Graphic and as built depiction of welds – note the weld sizes shown i...

Figure 7.9 Shows the addition of the length of the weld to the symbol at the lef...

Figure 7.10 Adding pitch of the weld.

Figure 7.11 Symbols of various types of Groove Welds.

Figure 7.12 Symbol of Sq. groove weld – note the annotation of root opening.

Figure 7.13 Symbol and as built of V-groove welds, note how the root gap (openin...

Figure 7.14 Shows the (1) depth of V groove on both sides of the weld, (2) shows...

Figure 7.15 Shows the specific depth of the groove weld (effective throat) desir...

Figure 7.16 Symbol of a bevel groove note which side of the plate is to be bevel...

Figure 7.17 Shows U-groove symbol.

Figure 7.18 Shows the J-groove symbol and the weld. Note the indicated depth of ...

Figure 7.19 Symbol of Flare-V groove weld and as built weld.

Figure 7.20 Symbol of and as built flare bevel and the weld.

Figure 7.21 Shows the melt-thru weld.

Figure 7.22 Shows the supplementary symbol of backing bar for the weld.

Figure 7.23 Symbol of a plug weld.

Figure 7.24 Shows symbols of plug and slot welds, with weld sizes, spacing and d...

List of Tables

Chapter 1

Table 1.1 Welding and joining processes, type of energy used, and their abbrevia...

Table 1.2 Arc efficiency by welding process.

Table 1.3 Shows the arc efficiency factors for various commonly used arc welding...

Table 1.4 Indicates general limits of joining/welding processes that apply to th...

Table 1.5 Arc efficiency factor.

Chapter 2

Table 2.8.3.1 Welding lead and their capacity.

Table 2.9.1 Welding lens shades.

Table 2.9.2 Helmets with auto adjusting lenses.

Table 2.10.1 Electrode classification and A-numbers.

Table 2.10.2 Shielded arc welding electrodes.

Table 2.11.10 Common SMAW process anomalies and their suggested causes and corre...

Table 2.11.12 Weld defects and suggested changes that can correct them.

Table 2.12.1 Aluminum alloy designation system.

Table 2.12.5 Cast aluminum designation and numbering system.

Table 2.12.6 Temper designation letters and meaning.

Table 2.12.23 Stainless steel welding electrodes and heat treatments.

Table 2.13 Nominal compositions of some of duplex steels.

Table 2.13.1 Nominal mechanical properties of duplex stainless steels.

Chapter 3

Table 3.10.1 Basic matching guide for electrode size and nozzle.

Table 3.11.1 Tungsten electrode tips.

Table 3.11.2 Tungsten electrode tips.

Table 3.11.3 Types of Tungsten electrode and their identification.

Table 3.16.1 Welding cable current carrying capacity.

Table 3.17.1 Details the NEMA rating and corresponding current output capacity.

Table 3.21.1 Aluminum alloy designation system.

Table 3.22.1 Cast aluminum designation and numbering system.

Table 3.24.1 Aluminum welding procedures using AC high frequency stabilized arc.

Table 3.24.2 GTAW stainless steel welding procedures.

Table 3.25.1 Nominal compositions of some of duplex steels.

Table 3.25.8 Stainless steel welding wire rod and heat treatments.

Table 3.26.2 Nominal mechanical properties of duplex stainless steels.

Table 3.29.1 Advantages and limitations of PAW process.

Chapter 4

Table 4.4.1 Deposition rate of various GMAW metal transfer mode.

Table 4.4.1.1 WPS for carbon steel and low alloy steels with short circuit trans...

Table 4.4.1.2 Aluminum WPS for short circuit.

Table 4.4.1.3 The transition current for spray transfer currents.

Table 4.4.1.4.1 Carbon steel - Basic training WPS for spray transfer welding.

Table 4.4.1.4.2 Aluminum - Basic training WPS for spray transfer welding.

Table 4.5.1 Details the current and the shielding gas type used in spray transfe...

Table 4.5.5.1 Gas selection guide.

Table 4.12.1.4 Welding lead current carrying capacity.

Chapter 5

Table 5.5.1 Carbon steel electrodes their use descriptions.

Table 5.6.6.1 Impact of shielding gases on the mechanical properties of weld met...

Chapter 6

Table 6.10.7 Indicates the basicity of various fluxes.

Table 6.11 Common welding electrodes for SAW process.

Chapter 7

Table 7.1 Pipe schedule.

Table 7.2 Terms and abbreviations relating to welding and construction.

Table 7.3 F-Number, ASME specification and AWS classification.

Table 7.4 P-number, group number, and type of material.

Table 7.5 Qualification of metals based on the procedure qualification.

Table 7.6 Temperature conversion.

Table 7.7 Temperature and pressure.

Guide

Cover

Table of Contents

Title Page

Copyright

List of Figures

List of Tables

Foreword

Preface

Begin Reading

Index

End User License Agreement

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Scrivener Publishing100 Cummings Center, Suite 541JBeverly, MA 01915-6106

Publishers at Scrivener

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Arc Welding Processes Handbook

Ramesh Singh

This edition first published 2021 by John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, USA and Scrivener

Publishing LLC, 100 Cummings Center, Suite 541J, Beverly, MA 01915, USA

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Library of Congress Cataloging-in-Publication Data

ISBN 978-1-119-81905-9

Cover image: Double headed GMAW system provided by the author

Cover design by Russell Richardson

Set in size of 11pt and Minion Pro by Manila Typesetting Company, Makati, Philippines

Printed in the USA

10 9 8 7 6 5 4 3 2 1

List of Figures

Figure 1.1 General lay out of welding and joining processes

Figure 2.3 A SMAW welder welding on a pipeline project

Figure 2.4 Typical SMAW setup

Figure 2.5 Welding arc action and various components of welding

Figure 2.6 Above (2 graphs), graph 1 above, shows the volt-ampere curve, (output curve or slope) at lower stings. Graph 2 below, shows the volt-ampere curve, (output curve or slope) the steep slope of a “Drooper” type of constant current arc welder

Figure 2.7 The schematic above shows the key components of an AC transformer

Figure 2.7.3 Schematic of a movable shunt type transformer control

Figure 2.7.4 A schematic of a movable coil reactor, the position of the reactor coil causes the inductive reactance of the secondary output coil resulting in the variance in current output

Figure 2.7.5 A magnetic amplifier transformer output control, the diode allows the current to flow in one direction, and this allows a remote control operation possible

Figure 2.7.6 The top portion of the figure shows the use of diodes – shown in Red color, and it compare it with Silicon controlled rectifiers (SCRs)

Figure 2.7.7 A schematic drawing of single-phase DC power source with SCR bridge control

Figure 2.8.1 Shows the schematic of single phase bridge type rectifier

Figure 2.8.2 Three phase bridge-type rectifier

Figure 2.8.1.1 Schematic diagram of a DC generator

Figure 2.8.1.2 Circuitry of an exciter system

Figure 2.8.3 Current conversion and resulting wave forms

Figure 2.8.3.1 Copper and aluminum welding leads: note the number of fine wires that compose a cable, and the rubber sheathing that covers them

Figure 2.8.3.2 Different types of SMAW electrode holders

Figure 2.8.4.1 Various types of cable connectors, and ground clamp. Pictures courtesy of LENCO® catalogue

Figure 2.8.5.1 NEMA rating

Figure 2.9.1 A typical hand-held welding shield

Figure 2.9.2 Miller Digital Elite helmet

Figure 2.9.3 A typical welding helmet

Figure 2.10.2 Portfolio of SMAW electrodes

Figure 2.10.3 AWS electrode classification method

Figure 2.10.5.1 Shop use electrode drying oven

Figure 2.10.5.2 Portable electrode holder also called quivers

Figure 2.11.1 Different types of weld joints

Figure 2.11.2 Different types of weld designs

Figure 2.11.3 Welding positions for welding a plate, the positions are primarily designated in relation to the position of the weld to the horizontal surface of the earth

Figure 2.11.4 Positions of plate and pipe butt welds and fillet welds with both AWS and European designations

Figure 2.11.5 Above figure shows the permitted angular tolerance for specifically designated welding positions for pipe welding

Figure 2.11.3.1 Testing a fillet weld

Figure 2.11.3.2 Testing a fillet weld using a hammer

Figure 2.11.3.3 Size and nomenclature of fillet weld

Figure 2.11.3.4 A single pass fillet weld

Figure 2.11.3.5 A single pass fillet weld with (arc termination) stop in the middle and restarted (arc re-initiation) from that point

Figure 2.11.3.6 A multi-passes fillet weld-note the termination of arc start and stops are staggered

Figure 2.11.3.7 A micro-etch of a double sided two pass fillet weld – compare the weld with the nomenclatures figure given above, to see how these two welds meet the standard requirements

Figure 2.11.4.1 Weld appearances matched with arc current, and arc travel speed

Figure 2.11.4.2 Pictures of the weld appearances and probable cause for the quality of weld produced

Figure 2.11.5.1 Offsetting the weld setup for distortion control

Figure 2.11.9 This is a rotator with one end of the pipe held in a three-jaw, self-centering chuck the free end of the pipe rests on a free rotating roller, it can be raised or lowered to level the pipe to align the weld ends

Figure 2.11.10 This rotator is similar to the one above except that the pipe end is placed on a motor driven set of rollers on one end, and the other end is on the set of idle rollers, which can be lowered or raised to align and level the weld joint

Figure 2.11.11 A heavy-duty rotator

Figure 2.11.12 Weld tacks bridging two pieces of pipe

Figure 2.11.13 Shows a removable tack

Figure 2.11.14 This picture shows both the bridge tack using external pieces of metal below, and just above that is the tack within the groove using welding

Figure 2.11.15 Typical CS pipe weld

Figure 2.11.10.1 Bevel edge preparation for vertical-up pipe in 6G position

Figure 2.11.10.2 The vertical up progression – note the direction of electrode movement

Figure 2.11.11.1 Vertical down progression

Figure 2.11.11.2 Weld profile of each pass

Figure 2.11.11.3 The sketch above shows a typical weld layers of several passes - note the sequencing numbers on each pass

Figure 2.12.6 Aluminum fillet weld-bend testing

Figure 2.12.12 Typical stainless-steel pipe weld, and weld-o-let on the header

Figure 2.12.13 Pipe is assembled and prior to welding, the welder is tacking them with the GTAW process

Figure 2.12.18 Schaeffler diagram

Figure 2.12.19 DeLong diagram

Figure 2.14 Nickel alloy plate being welded

Figure 2.1 Nickel is in 10th group and 4th period in the periodic table, its atomic number is

Figure 2.14.2 Typical nickel welding electrodes – note the electrode identification making on the electrode

Figure 2.14.3 Nickel alloy welding (note the fillet weld in upward progression)

Figure 3.3.1 Typical GTAW welding

Figure 3.3.2 A GTAW welder, note the welding torch, and the filler wire in each hand

Figure 3.4.1 Typical GTAW welding process with details of the welding torch

Figure 3.5.1 A typical GTAW set-up with positions of gas cylinder, welding machine, electrode holder and work-piece

Figure 3.5.2 The cleaning process by the current cycle

Figure 3.5.3 High and low frequency currents in pulsing

Figure 3.6.1 DC HF output circuit

Figure 3.7.1 The graph

Figure 3.7.2 Four AC wave forms

Figure 3.7.2.2 Effect of Independent AC amperage control on weld penetration and weld bead profile

Figure 3.7.2.3 Effect of variation in AC frequency on the weld profile and penetration

Figure 3.7.2.4 Provides an example of a weld done at 150 Hz and 40 Hz

Figure 3.7.2.5 Weld profile as a result of extended EN of the cycle

Figure 3.7.2.6 Weld profile as a result of reduced EN cycle

Figure 3.7.4.1 A schematic drawing of single-phase DC power source with SCR bridge control

Figure 3.7.6.1 Schematic diagram of a DC generator

Figure 3.7.6.2 DC excitation circuit

Figure 3.9.1 Gas flow meters (A) shows the tube type flow meter, and the bottom (B) has a gauge type flow meter both calibrated in L/min

Figure 3.10.1 A typical manual welding torch, note the water cooling, gas supply and tungsten electrode assembly

Figure 3.10.2 Various nozzles types and sizes

Figure 3.10.3 A gas lens, with mesh, and holding circlip

Figure 3.10.4 An assortment of manual welding GTAW torch components

Figure 3.11.1 Electrode tips

Figure 3.11.2.1 The tip angle 60°, note the depth of the deeper penetration and the shape and depth of the HAZ

Figure 3.11.2.2 The tip angle 30°, note the depth of the shallower penetration and the shape of the HAZ

Figure 3.11.2.3 The tip angle 15°, note the depth of the shallowest penetration and the shape of the HAZ

Figure 3.12.1 Five basic weld designs, (Courtesy of Indian Air force training manual “Basic Welding Technology”)

Figure 3.16.1 Copper and Aluminum welding leads: note the number of fine wires that compose a cable, and the rubber sheathing that covers them

Figure 3.16.2 Various types of cable connectors, and ground clamp. Pictures Curtsy of LENCO catalogue

Figure 3.25.9.3.1 Welder is tacking a pipe prior to welding

Figure 3.25.9.3.2 A nozzle is welded on a pipe header

Figure 3.25.10.2.1 Schaeffler diagram

Figure 3.25.10.2 DeLong diagram

Figure 4.3.1 Typical GMAW welding

Figure 4.4.1 A GMAW operator welding on an offshore pipeline

Figure 4.4.1.1 Short circuit transfer (arc-action and cycle)

Figure 4.4.1.2 Current voltage range for various transfer mode

Figure 4.11.1 Typical GMAW (MIG) welding set up with the external wire feed unit

Figure 4.12.1 A typical GMAW torch with trigger type on-off switch on the handle

Figure 4.12.2 Blow out of the GMAW torch that shows some of the components that make up a welding torch

Figure 4.12.3 The GMAW torch and the cable connector

Figure 4.12.1.4 Copper and aluminum welding leads: note the number of fine wires that compose a cable, and the rubber sheathing that covers them

Figure 4.13.8.1 (a) Contour of a weld bead in the flat position with the work horizontal; (b) welding slightly uphill; (c) welding slightly downhill

Figure 4.13.12.1 WRC diagram

Figure 5.3.1 FCAW-S self-shielding tubular wire process

Figure 5.3.2 FCAW-G, gas shielding solid wire process

Figure 5.4.1 Typical FCAW setup

Figure 5.5.1 FCAW electrode classification system

Figure 5.8.7.2.1 Shows the metal transfer through the arc with CO2 shielding on the left, and 75% Ar. + CO2 on the right

Figure 6.3.1 Schematic display of the SAW process

Figure 6.3.2 Shows the submerged arc welding of a plate

Figure 6.3.3 Shows the SAW of a pipe in a fabrication shop – note the arc and flux position as the pipe rotates

Figure 6.3.4 Shows the completed pipe weld

Figure 6.3.5 Higher deposition rate of SAW process

Figure 6.6.1 Showing SAW process in progress on a pipe weld

Figure 6.6.2 Shows the collected flus for cleaning and reusing

Figure 6.7.1 Multi-wire SAW system

Figure 6.7.3 Tandem head strip wire SAW process for cladding

Figure 7.1 Structure of the welding symbol

Figure 7.2 Welding symbol arrows

Figure 7.3 Welding symbol position of the arrows

Figure 7.4 Significance of the circle on the arrows

Figure 7.5 Symbols for type of welds

Figure 7.6 Symbol of a fillet weld

Figure 7.7 Shows the side of the metal where the fillet weld is required to be made

Figure 7.8 Graphic and as built depiction of welds – note the weld sizes shown in the symbol on left and its corresponding annotation on the actual weld

Figure 7.9 Shows the addition of the length of the weld to the symbol at the left, and what it means is shown in the as built figure on the right

Figure 7.10 Adding pitch of the weld

Figure 7.11 Symbols of various types of Groove Welds

Figure 7.12 Symbol of Sq. groove weld – note the annotation of root opening

Figure 7.13 Symbol and as built of V-groove welds, note how the root gap (opening) is shown

Figure 7.14 Shows the (1) depth of V groove on both sides of the weld, (2) shows the depth of the penetration desired of the weld

Figure 7.15 Shows the specific depth of the groove weld (effective throat) desired

Figure 7.16 Symbol of a bevel groove note which side of the plate is to be beveled and to what degree

Figure 7.17 Shows U-groove symbol

Figure 7.18 Shows the J-groove symbol and the weld. Note the indicated depth of the weld

Figure 7.19 Symbol of Flare-V groove weld and as built weld

Figure 7.20 Symbol of and as built flare bevel and the weld

Figure 7.21 Shows the melt-thru weld

Figure 7.22 Shows the supplementary symbol of backing bar for the weld

Figure 7.23 Symbol of a plug weld

Figure 7.24 Shows symbols of plug and slot welds, with weld sizes, spacing and depth of the weld

List of Tables

Table 1.1 Welding and joining processes, type of energy used, and their abbreviations as defined by the American Welding Society

Table 1.2 Arc efficiency by welding process

Table 1.3 Shows the arc efficiency factors for various commonly used arc welding processes

Table 1.4 Indicates general limits of joining/welding processes that apply to the material listed in left column

Table 1.5 Arc efficiency factor

Table 2.8.3.1 Welding lead and their capacity

Table 2.9.1 Welding lens shades

Table 2.9.2 Helmets with auto adjusting lenses

Table 2.10.1 Electrode classification and A-numbers

Table 2.10.2 Shielded arc welding electrodes

Table 2.11.10 Common SMAW process anomalies and their suggested causes and corrections

Table 2.11.12 Weld defects and suggested changes that can correct them

Table 2.12.1 Aluminum alloy designation system

Table 2.12.5 Cast aluminum designation and numbering system

Table 2.12.6 Temper designation letters and meaning

Table 2.12.23 Stainless steel welding electrodes and heat treatments

Table 2.13 Nominal compositions of some of duplex steels

Table 2.13.1 Nominal mechanical properties of duplex stainless steels

Table 3.10.1 Basic matching guide for electrode size and nozzle

Table 3.11.1 Tungsten electrode tips

Table 3.11.2 Tungsten electrode tips

Table 3.11.3 Types of Tungsten electrode and their identification

Table 3.16.1 Welding cable current carrying capacity

Table 3.17.1 Details the NEMA rating and corresponding current output capacity

Table 3.21.1 Aluminum alloy designation system

Table 3.22.1 Cast aluminum designation and numbering system

Table 3.24.1 Aluminum welding procedures using AC high frequency stabilized arc

Table 3.24.2 GTAW stainless steel welding procedures

Table 3.25.1 Nominal compositions of some of duplex steels

Table 3.25.8 Stainless steel welding wire rod and heat treatments

Table 3.6.2 Nominal mechanical properties of duplex stainless steels

Table 3.29.1 Advantages and limitations of PAW process

Table 4.4.1 Deposition rate of various GMAW metal transfer mode

Table 4.4.1.1 WPS for carbon steel and low alloy steels with short circuit transfer mode

Table 4.4.1.2 Aluminum WPS for short circuit

Table 4.4.1.3 The transition current for spray transfer currents

Table 4.4.1.4.1 Carbon steel – Basic training WPS for spray transfer welding

Table 4.4.1.4.2 Aluminum – Basic training WPS for spray transfer welding

Table 4.5.1 Details the current and the shielding gas type used in spray transfer mode of some of the common materials

Table 4.5.5.1 Gas selection guide

Table 4.12.1.4 Welding lead current carrying capacity

Table 5.5.1 Carbon steel electrodes their use descriptions

Table 5.6.6.1 Impact of shielding gases on the mechanical properties of weld metal

Table 6.10.7 Indicates the basicity of various fluxes

Table 6.11 Common welding electrodes for SAW process

Table 7.1 Pipe schedule

Table 7.2 Terms and abbreviations relating to welding and construction

Table 7.3 F-Number, ASME specification and AWS classification

Table 7.4 P-number, group number, and type of material

Table 7.5 Qualification of metals based on the procedure qualification

Table 7.6 Temperature conversion

Table 7.7 Temperature and pressure

Foreword

The book, “Arc Welding Processes Handbook”, brings together salient knowledge of arc welding methods used primarily in the industry and especially in the oil patch. The information presented about the welding process is usable and emulates the presence of your own welding engineer. Covering such welding methods as SMAW, GTAW, GMAW, FCAW and SAW with details in materials and techniques. This book is useful to both new welders as well as experienced welders. In the book, Ramesh covers these welding processes, how they work, and dives into the electrical side of welding. Welding machines, Transformers, Generators, Invertors, AC, DC, Sq. wave, Sine wave currents, Rectifiers, SCRs, Diodes, etc., as current control methods, all these are presented in a way that is easy to understand the functions of various welding machines. Most common weldable materials are discussed with welding guidance given that includes Aluminum, Nickel, Carbon steels, Stainless steels, Precipitation Hardened steels, Duplex Stainless steels, and others. The book is super comprehensive, easy to follow, and a welcome addition to any welding engineer’s bookcase. It is a truly great guide for any budding engineer or welder to help them master their skills.

David AmmermanProject Director at Gulf Interstate Engineering, MME, Texas PE30+ years past-member of ASME, and member of API Committee:Pipeline Construction Voting Group

Preface

The book ArcWelding ProcessesHandbook has been developed to address the need of a vast majority of people who want to know about welding, some of them also want to weld as hobbyists, or carry their passion for welding to be a professional welder. The book can also be used as a reference by field engineers and managers responsible for welding and fabrication activities. The book uses several figures and illustration that are available in the public domain, yet wherever it could be identified, the credit has been assigned to the source.

The book will provide readers and practitioners of the profession with an understanding of nearly all aspects of arc welding. The book covers the theory, the principles of the processes, the equipment, and the techniques that would improve the competency in welding, for each welding process. A good number of tables and illustrations are included to accentuate the points as well as to give readers familiarity with things that may or may not be available in their work or school trade workshops.

Chapter 1 introduces the reader to all possible welding process, including arc welding, electric resistance welding etc.

The practice welding procedure (WPS) given especially in Chapter 2 on SMAW process should prove a good basis to start welding and develop into an experienced welder. From here, one can move forward with other processes using the practice welding procedures included in Chapter 3 on GTAW, as well as GMAW processes in Chapter 4. For those who want to start welding, they can start with settings in these procedures and preparations and make changes to develop their skills around them. But it is not necessary to strictly follow this sequence, if someone has already developed the skills in any other process and wants to move to any other process.

The skills required to master FCAW process in Chapter 5 almost mimics the basic skills of GMAW in Chapter 4, and once this process is mastered, moving forward with the FCAW process should not be difficult at all.

The process of SAW in Chapter 6 is very different and very few welding schools will have this process in house. For students to practice on it, in most cases it will have to be learned and mastered on the job. But the chapter on SAW process gives the reader abundant information and familiarity with the process that they can step up to the opportunity when it becomes available.

Included in Chapter 7 is the welding symbols and how to use them, to read those symbols on fabrication drawings and weld accordingly. Reading and understanding the language of welding is an important step in becoming a successful welding professional. The chapter also includes other miscellaneous but important information that would come handy to any welding professional. The most important information is the detailed description of welding symbols and how to use and read them.

This book is best used in a workshop where the reader can pick up the welding torch or holder and try to convert the words from the book to an actual weld.

Ramesh SinghKaty, TXJune 2021

1Introduction to Welding Processes

1.1 Synopsis

The chapter introduces the most common welding and joining processes, by discussing the acceptable definition of welding, and the elementary understanding of skill development steps required to be a welder or a welding machine operator.

1.2 Keywords

Joining processes, definitions, welding, arc welding, arc efficiency, heat, heat affected zone (HAZ), solidification.

1.3 Welding

When we speak of welding, various images comes to our minds. Depending on persons’ knowledge and experience with the process that can be various, simple or complex. But one thing that can be common to all those images and pictures is that the process of joining two pieces of metal to create a useful object.

This establishes one aspect of the term welding, that is, that the welding is a metal joining process. Let us explore a little more about what is welding, and how it is different from other Joining processes?

There have been discussions and sometimes arguments on describing if welding is an art or a science. Mundane as it might appear the question is pertinent and, in my experience, some well-meaning experts often miss the point as to which part about the term “welding” they are referring about to support their arguments. Welding as the physical and practical part of joining two materials in most part is an art, it requires dexterity in hand, and hand-eye coordination to do a good job. However, the study of the heat and melt flow solidifications prediction, prediction of material behavior under heating and cooling cycles associated with the term welding is a science, an essential pat under the science of physics. Hence it is both an art, and a science of joining metals by use of adhesive and cohesive forces between metals by welding, brazing, and soldering some of these joining processes produce metallurgical bonds. Person with the balanced knowledge of both science, and art parts of welding is expected to do much better work on either side of the argumentative divide. Further we get into the depth of the study, the line of separation from art to physics starts to become more evident.

Both process metallurgy and physical metallurgy is involved in welding. Welding is a unique metallurgical activity as it involves a series of metallurgical operations similar to metal production, like steelmaking and casting but in a rapid succession and on a very small scale. In science side of welding the thrust of the study is on the materials behavior during application of localized heat, and cooling and solidification physics.

1.4 Defining Welding

The AWS definition for welding is “a materials joining process which produces coalescence of materials by heating them to suitable temperatures with or without the application of pressure or by the application of pressure alone and with or without the use of filler material”.

Welding is often compared in a very rudimentary way with casting. The comparison with casting involves the fact that in welding a volume of molten metal is solidified (cast) within the confines of a solid base metal (mold). The base metal may have been preheated to retard the cooling rate of the weld joint just as in casting molds are preheated to slow down cooling and reduce “Chilling” of the casting. Upon solidification, the weld deposit or casting can be directly put into service, as the welds are often used in as-welded condition or may be heat-treated or worked further on as required. However, such comparison is not an accurate depiction of welding process, nor it is a fair comparison. For example, in welding the base metal “mold” is part of the weld, unlike the mold of a casting, which is removed after solidification, so unlike casting process, what happens to the “mold” is of significant importance in welding. Unlike casting, in welding the solidification and the nucleation of weld metal takes effect on the basis of the base metal grain structure that is just adjacent to the molten metal of welding and a unique set of metallurgy is created in the base metal that is heated to above austenitic temperature range, this small band of base metal is called heat affected zone (HAZ).

Welding involves small area relative to the full size of the structure, the base material. Thus, a weld is a very small mass of metal, mostly two metals that are heated very rapidly by intense heat and cooled rapidly, this rapidly heated and cooled small area often overlap each other in succession to create yet another complex metallurgical condition. The dissipation of heat is by all three modes; Conduction, Radiation and Convection. Often the large surrounding mass of colder base metal is heated by conduction process, which is the major source of heat transfer from weld. The heating and after welding the cooling process are dynamic, equilibrium conditions are seldom seen in conventional welding operations, in fact welding conditions represent a great departure from equilibrium. That is the reason weld zones often display unusual and verity of structures and properties, all this within the confines of a very small area affected by welding process.

It is thus important that a welding personnel have a very good understanding of “Heat” in welding. The understanding of the heat generation and physics of welding are important steps in making of a good welding engineer, and it helps being a good welder as well.

Welding is carried out based on a well thought out and specific plan in order to attain the required material properties. Many regulatory and industrial specifications have well developed process to get the plan in activation. Such plans are called Welding Procedures, and a well laid out sequence of operation is established for the welding qualifications, of both the procedure’s ability to meet required metallurgical and mechanical properties and also a welder’ ability to repeatedly produce the quality of weld desired through that welding procedure. Following is a brief discussion on welding procedures and their role in welding application.

1.5 Welding and Joining Processes

There are number of different approaches to welding, some of them are near universal in their application to most common materials, and are capable of adjusting to number of variables to be used on different positions, and conditions, while others are very specific and are no so universal in their application. With the welding we have included some other material joining processes that are in fact not a welding process. These are very often encountered in the industrial environment, and are often demanded that an accomplished welder knows how to use these processes. The Figure 1.1 below shows various welding and joining process.

The Table 1.1 below list s various welding and joining processes grouped as per the mode of energy used for that specific welding process. The table also includes other joining process that do not use Electric as the source of energy for joining. And there is other that are distinguished by the way they transfer the molten metal in to the metals being joined.

1.6 Arc Welding

The arc welding group includes eight specific processes, each separate and different from the others but in many respects similar. An introduction to those basic arc welding processes is presented here for some of those most common first-generation arc welding processes. Note that further variations have been made in some of these processes, some of them are discussed further in the book, but there are others that are proprietary developments, the information is covered under copyright laws, hence details on these developments are not included in the book.

1.6.1 Carbon Arc Welding

The carbon arc welding (CAW) process is the oldest of all the arc welding processes and is considered to be the beginning of arc welding. The Welding Society defines carbon arc welding as “an arc welding process which produces coalescence of metals by heating them with an arc between a carbon electrode and the work-piece. No shielding is used. Pressure and filler metal may or may not be added. It has limited applications today, but a variation or twin carbon arc welding is more popular. Another variation uses compressed air to force molten metal out to effect cutting.

1.6.2 Shielded Metal Arc Welding (SMAW)

The development of the metal arc welding process soon followed the carbon arc. This developed into the currently popular shielded metal arc welding (SMAW) process defined as, an arc welding process which produces coalescence of metals by heating them with an arc between a covered metal electrode and the work-piece. Shielding is obtained from decomposition of the electrode covering. Pressure is not used and filler metal is obtained from the electrode.

Figure 1.1 General lay out of welding and joining processes.

1.6.3 Gas Tungsten Arc Welding (GTAW)

The need to weld nonferrous metals, particularly magnesium and aluminum, challenged the industry. A solution was found called gas tungsten arc welding (GTAW) and is defined as, an arc welding process which produces coalescence of metals by heating them with an arc between a non-consumable tungsten electrode, and the work piece. Shielding for the welding arc is obtained often from an inert-gas, or mixture gases that may not always be inert.

Table 1.1 Welding and joining processes, type of energy used, and their abbreviations as defined by the American Welding Society.

Group

Welding process

AWS letter designation

Arc Welding

Electric Arc Welding

Carbon Arc

CAW

Flux Cored Arc

FCAW

*

Gas Metal Arc

GMAW

*

Gas Tungsten Arc

GTAW

*

Plasma Arc

PAW

**

Shielded Metal Arc

SMAW

*

Stud Arc

SW

Submerged Arc

SAW

*

Electrical Resistance Welding

Flash Welding

FW

High Frequency Resistance

HFRW

Percussion Welding

PEW

Projection Welding

RPW

Resistance-Seam Welding

RSEW

Resistance-Spot Welding

RSW

Upset Welding

UW

Oxy-fuel Gas Welding (OFW)

Oxyacetylene Welding

OAW

Oxyhydrogen Welding

OHW

Pressure Gas Welding

PGW

Solid State Welding

Cold Welding

CW

Diffusion Welding

DFW

Explosion Welding

EXW

Forge Welding

FOW

Friction Welding

FRW

Hot Pressure Welding

HPW

Roll Welding

ROW

Ultrasonic Welding

USW

Capillary Action Transfer and Distribution of Metal

Brazing

Diffusion Brazing

DFB

Dip Brazing

DB

Furnace Brazing

FB

Induction Brazing

IB

Infrared Brazing

IRB

Resistance Brazing

RB

Torch Brazing

TB

Soldering

Dip Soldering

DS

Furnace Soldering

FS

Induction Soldering

IS

Infrared Soldering

IRS

Iron Soldering

INS

Resistance Soldering

RS

Torch Soldering

TS

Wave Soldering

WS

Other Welding Processes

Electron Beam

EBW

Electroslag

ESW

Induction

IW

Laser Beam

LBW

Thermit

TW

*Processes discussed in this book.

**Included with GTAW process.

1.6.4 Gas Metal Arc Welding (GMAW)

In the desire to increase the production rate, and widen the types of material being welded by one process the GMAW process was invented. Since its early days the process has gone through a number of improvements, and currently it is one of the most versatile welding processes among the arc welding processes. It has number of variants by the way the weld metal is deposited, and shielding gases used for various types of metal welding.

1.6.5 Submerged Arc Welding (SAW)

Earlier attempt to increase welding production lead the development of Automatic welding utilizing bare electrode wires in the early nineteenth century, but was not much popular primarily due to the open arc and the resultant quality of weld, which was always an issue.

The dissatisfaction with bare-wire welding and some innovative ideas lead to the development of the submerged arc welding (SAW) process, this was much better automated process and it made the automatic welding popular. Submerged arc welding is defined as “an arc welding process which produces coalescence of metals by heating them with an arc or arcs between a bare metal electrode or electrodes and the work piece. Pressure is not used and filler metal is obtained from the electrode and sometimes from a supplementary welding rod.” It is normally limited to the flat or horizontal position.

1.7 Efficiency of Energy Use

Processes use electrical energy to initiate arc, but not all the arc energy is fully used to melt the metals being welded. There is significant energy loss in the process.

The process efficiency of various arc welding process differs significantly, based on number of factors like material being welded, type of gas being used if gas is used in the process. The effect of these variables depends on one or a combination of more factors.

The use of energy generated by a process is an important factor in determining how much current is needed to generate required heat for welding. The generation of heat also determines the effective use of a process for welding different materials. The table below gives the glimpses of Arc efficiency of various Arc Welding processes.

As is obvious, not all welding and joining process are equal, this leads to the fact that some are more versatile in usability for welding number of materials, while some are more specific to certain type of materials. The table below gives a general usability of various arc welding processes.

For example, GTAW process is nearly all the material listed, but SMAW and SAW processes stops short, and not suitable for welding Copper and alloys, or Titanium and its alloys. Table 1.2 is the generic information, while the Table 1.3 is more specific with numbers and includes more process and varients. Similarly Brazing is possible for nearly all material listed but soldering is not. The Table 1.4 blow presents a matrix that shows the ability and limits of various arc welding processes, the last two columns of the table show the applicability scope of soldering and brazing processes.

The Table 1.5 below is borrowed from another book Applied Welding Engineering – Process, Codes and Standards. The table lists the electric arc process by the arc energy efficiency of each process. Note the highest efficiency of SAW process and the lowest in that of GTW process.

Table 1.2 Arc efficiency by welding process.

Process

Arc efficiency

1

SMAW

Intermediate

2

GTAW

Low

3

SAW

High

1.8 Welding Procedures

A welding procedure is a statement of execution, a specific plan prepared by the welding contractor. The procedure details with listing of various variables associated with the proposed welding process giving an assurance that the resulting weld would guarantee that the required mechanical and metallurgical properties will be met. Any format of form may be used to develop a welding procedure giving essential details. Some international specifications especially addressing the welding requirements have developed a format for the purpose, AWS D1.1 has E-1 form for pre-qualified procedures, similarly ASME Section IX of Boiler and Pressure vessels code has a set of such forms for welding specifications, welding qualification records (PQRs) and welders’ qualification records, they are numbered as QW- 482, QW- 483 and QW 484 respectively. Other international standards for welding are EN ISO 15609-1, EN ISO 15609-2, EN ISO 15609-3, EN ISO 15609-4, EN ISO 15609-5, and EN ISO 15614. Till the last revision, the EN ISO 15614 had 12 parts dealing with specific topics on welding various materials like Steel, Aluminum, Cast Iron, Titanium, Copper etc.

The plan details all essential and non-essential variables that are important to achieve the quality of weld. These variables are welding process specific. Some of these variables are discussed in this book. In ASME section IX, these variables are listed specific to the particular welding process, they are subdivided into essential, supplementary essential, and nonessential variables. However, these variables are not specific to ASME but are in general agreement with welding technology.

Table 1.3 Shows the arc efficiency factors for various commonly used arc welding processes.

Welding process

Arc efficiency factor η

Range

Mean

Submerged Arc Welding

0.91 - 0.99

0.95

Shielded Metal Arc Welding

0.66 - 0.85

0.80

Gas Metal Arc Welding (CO

2

Steel)

0.75 - 0.93

0.85

Gas Metal Arc Welding (Ar Steel)

0.66 - 0.70

0.70

Gas Tungsten Arc Welding (Ar Steel)

0.25 - 0.75

0.40

Gas Tungsten Arc Welding (Ar Aluminum)

0.22 - 0.46

0.40

Gas Tungsten Arc Welding (He Aluminum)

0.55 - 0.80

0.60

Table 1.4 Indicates general limits of joining/welding processes that apply to the material listed in left column.

Material

Welding processes

Other joining processes

SMAW

SAW

GMAW

FCAW

GTAW

PAW

ESW

EGW

RW

OFW

DFW

FRW

EBW

LBW

B

S

Carbon Steel

x

x

x

x

x

x

x

x

x

x

x

x

x

x

Low alloy steel

x

x

x

x

x

x

x

x

x

x

x

x

x

Stainless steel

x

x

x

x

x

x

x

x

x

x

x

x

x

x

Cast Iron

x

x

x

x

x

x

x

Nickel and alloys

x

x

x

x

x

x

x

x

x

x

Aluminum and alloys

x

x

x

x

x

x

x

x

x

x

x

x

x

x

Titanium and alloys

x

x

x

x

x

x

x

x

x

Copper and alloys

x

x

x

x

x

x

x

Magnesium and alloys

x

x

x

x

x

x

x

Refractory alloys

x

x

x

x

x

x

Table 1.5 Arc efficiency factor.

Welding process

Arc efficiency factor η

Range

Mean

Submerged Arc Welding

0.91 - 0.99

0.95

Shielded Metal Arc Welding

0.66 - 0.85

0.80

Gas Metal Arc Welding (CO

2

Steel)

0.75 - 0.93

0.85

Gas Metal Arc Welding (Ar Steel)

0.66 - 0.70

0.70

Gas Tungsten Arc Welding (Ar Steel)

0.25 - 0.75

0.40

Gas Tungsten Arc Welding (Ar Aluminum)

0.22 - 0.46

0.40

Gas Tungsten Arc Welding (He Aluminum)

0.55 - 0.80

0.60

Essential variables are those in which a change, as described in the specific variables, is considered to affect the mechanical properties of the weldments, hence any change shall require requalification of the welding procedure. The Supplementary essential variables are required for metals for which other Sections specify notch-toughness tests and are in addition to the essential variables for each welding process.

The Nonessential variables on the other hand are those in which a change, as described in the specific variables, may be made in the WPS without requalification.

Some special process like corrosion-resistant and hard-surfacing weld metal overlays may have different additional essential variables. Only the variables specified for special processes shall apply. A change in the corrosion-resistant or hard-surfacing welding process requires requalification.