Welding Metallurgy - Carbon and Alloy Steels: Fundamentals v. 1

1002 Pages·1995·72.73 MB·English

by  G. E. Linnert

Welding Metallurgy
Carbon and Alloy Steels
Volume I
Fundamentals
George E. Linnert
GML Publications
Hilton Head Island, South Carolina, USA
Fourth Edition
Published by the American Welding Society
Miami, Florida, USA
Library of Congress Catalog Card Number: 94-074489
International Standard Book Number: 0-87 17 1-457-4
Copyright 0 1994 by the American Welding Society
550 N.W. LeJeune Road; Miami, Florida; USA
Fourth Edition 1994
All rights reserved. No part of this book may be reproduced in any
form or by any means - electronic or mechanical - including pho-
tocopying, recording, or any other information storage or retrieval
system, without permission in writing from the publisher.
The American Welding Society, Inc. assumes no responsibility for the
information contained in this publication. An independent, substanti-
ating investigation should be made prior to reliance on or use of such
information.
Text edited, designed and formatted by Alexander M. Saitta
Printed in the United States of America
xx Welding Metallurgy
Tables
Table Page
No . Title No.
2.1 Elementary Particles ..................................................................................... 20
2.2 Ionization Potential of Gases and Vapors ..................................................... 37
2.3 Diameters of Atoms ....................................................................................... 39
2.4 The Elements ................................................................................................ 42
2.5 Features of the Seven Crystal Systems ........................................................ 56
2.6 Densities of Some Pure Metals and Their Change ....................................... 66
2.7 Crystal Structures of Some Pure Metals ....................................................... 75
2.8 Crystal Structures of Some Pure Metals Capable of ................................... 76
Allotropic Transformation
2.9 Relationships Between ASTM Grain Size Numbers ..................................... 99
2.10 Comparison of Methods for Localized Analysis of Surfaces. ...................... 122
3.1 The Properties of Metals ............................................................................. 134
3.2 Typical Elastic Constants for Various Materials at Room Temperature ..... 140
3.3 Influence of Crystallographic Orientation on Elastic Modulus .................... 141
at Room Temperature
3.4 Strain Rates Common to Various Exposures, Services, ........................... 173
and Mechanical Tests
3.5 Temperature Conversion Scales and Fixed Points of Interest ...................2 18
3.6 Notched - Bar Impact Values for Metals Tested at Low Temperatures ......2 21
3.7 Effect of Cold Work on Mechanical Properties of ...................................... 249
Low-Carbon Steel Sheet
3.8 Thermal Neutron Cross Section for Iron and Other Elements ..................2.5 1
Found in Steel
3.9 Density and Strength-Weight Ratio of Metals, Alloys and Nonmetals ........2 59
3.10 Specific Heat of Some Metals and Nonmetals. ........................................... 260
3.1 1 Thermal Conductivity of Metals, Alloys, and Nonmetals. ............................ 262
3.1 2 Melting Points or Ranges of Metals, Alloys, and Nonmetals ...................... 263
3.13 Melting Point, Latent Heat of Fusion, Boiling Point and Heat of
Vaporization of Metals ................................................................................. 265
3.14 Coefficient of Linear Thermal Expansion for Some Metals, ....................... 267
Alloys, and Nonmetals
3.1 5 Electron Thermionic Work Functions of Metals and Nonmetals ................2. 68
3.16 Electrical Properties of Metals, Alloys and Nonmetals. ............................... 270
3.1 7 Forms of Corrosion and Instigative Conditions ........................................... 275
3.1 8 Galvanic Series, and Electromotive Force Values for Metals ..................... 278
3.1 9 Commonly Used Materials and Environments in Which Failure by Stress-
Corrosion Cracking Has Been Experienced in Industry or in Tests ............2 87
4.1 Elements Used for Alloying Irons and Steels, and Their Influence on
Crystalline Structure of the Alloy ................................................................. 319
Tables XXi
Tabl.e Page.
No Title No
4.2 Changes in Pure Iron During Cooling and Temperatures of Occurrence ...3 21
4.3 Interstitial-Free I-F Steel .............................................................................. 358
5.1 Comparison of Rimmed. Capped. Semikilled and Killed Steels ................. 379
5.2 Gas Content of Alloy Steel Ingots ............................................................... 380
5.3 Typical Gas Contents of Alloy Steel Ingots Melted by Four Electric
Furnace Processes ..................................................................................... 394
5.4 Common Terms for Hot-Rolled Mill Products. ............................................. 405
5.5 Classification and Usage of Carbon Steels ................................................. 411
5.6 SAE-ASTM Unified Numbering System ...................................................... 417
5.7 AISI-SAE System for Designation of Carbon and Alloy Steels ................... 419
5.8 AISI-SAE System for Characterization of Carbon and Alloy Steels ............ 420
5.9 AlSl and SAE Systems for Classification of High-Strength Carbon
and Low Alloy Steel Sheet .......................................................................... 421
5.10 ASTM Annual Book of Standards - 1993 Edition. ....................................... 422
5.1 1 API Specifications Governing Materials ...................................................... 425
5.12 ASME Boiler and Pressure Vessel Code .................................................... 427
5.13 ASME 831 ; Code for Pressure Piping ........................................................ 428
5.14 AWS Codes, Specifications and Standards ................................................ 429
6.1 Characteristics of Argon and Helium Gases When Shielding
the GTAW Process. ..................................................................................... 483
6.2 Typical Chemical Compositions of Weld Metal Deposited by
Flux Cored Arc Welding Electrodes ............................................................ 504
6.3 Thickness and Weight of Zinc Coatings on Steel ....................................... 528
7.1 Temper Colors Formed on Iron and Carbon Steel ..................................... 676
8.1 Degree of Vacuum Used to Protect Metal During Various Processes .......7 19
8.2 Materials Used in Coverings on Steel Electrodes for SMAW
Arc Welding Process ................................................................................... 726
8.3 Recovery of Elements From Coverings of Electrodes Deposited
by SMAW Process ...................................................................................... 729
8.4 Typical Covering Formulas for Steel SMAW Electrodes. ............................ 732
8.5 Typical Flux Core Formulas for Steel FCAW Electrodes. ........................... 740
8.6 IIW Classification of Fluxes for Submerged Arc Welding of Steel .............. 754
8.7 Typical Flux Compositions for Submerged Arc Welding of Steel ...............7 55
8.8 Typical Flux for Electroslag Welding of Steel .............................................. 766
8.9 Gases Used in Shielding Welding Arcs ...................................................... 767
8.10 Controlled Atmospheres Used in Furnace Brazing Carbon and
Low-Alloy Steels .......................................................................................... 782
9.1 Influence of Alloying Elements in Steel on Martensite Formation. .............. 837
9.2 Microstructures Found in Steel Weld Metal ................................................ 858
9.3 Microstructures Found in Cast and Wrought Steels; Including their
Weld Heat-Affected Zones .......................................................................... 877
xxii Welding Metallurgy
Preface
Readers of Welding Metallurgy in their comments about previous Volumes 1 and
2 of the Third Edition have offered helpful suggestions toward betterment of future
editions. All offerings from students, engineers, experienced welding personnel, and
educators have been carefully weighed by the author in planning this present revision.
A principal aim in carrying out this work was to acquire updated information wherev-
er available, but input from readers prompted several changes. One change will be
found in the sequence of chapters, which now provides more logical progression from
the structures and properties of metals, through the mechanics and effects of heating
for welding, and finally to metallurgical description of typical welds in steel. Also, the
remodeled text now includes additional material of a fundamental nature to assist in
developing broader, analytical explanations for the chemical and physical events that
arise in welding. The need for this assistance had been voiced by readers who are con-
fronted with the complex technology of welding, but who have not had exposure to
chemistry and physics of the depth needed to rationalize the phenomena encountered.
Relationships between fundamental features of metals and their behavior in welding
are pointed out to encourage development of more complete understanding of each
particular happening in welding. This kind of awareness of the factors involved and
the mechanics entailed aids greatly when a decision must be made regarding the most
effective measure for dealing with a given troublesome situation.
Several features of the new text deserve comment. Metric practice has been
employed as the principal system for dimensions and quantities because of expanding
usage world-wide; however, U.S. customary units are in parentheses following SI
units throughout the text and are included in most tables and figures. The text does not
include references to particular articles in periodicals, reports, and books that served
as resources because of the great number from which information was extracted.
Instead, keywords from the International Welding Thesaurus are included in the text
to guide readers to helpful literature for additional details whenever needed. Widely
available computerized search services cognizant of these keywords can produce lists
of relevant references, including those published henceforth. Each chapter concludes
with a short list of selected publications under the heading “Suggested Reading.”
These are recent publications that provide broader range of coverage of the area being
reviewed in the chapter.
Colleagues and organizations that assisted the author in collecting and preparing
material for publication are so large in number that individual recognition here is not
practical. The author is keenly aware of the great importance of this support. In the
course of time, sincere appreciation will be expressed to contributors individually.
Two organizations provided protracted help with their staffs and their facilities. The
American Welding Society gave encouragement and assistance at every possible turn,
and waited patiently for completion of the author’s manuscript. Mr. Robert L. O’Brien,
Director of Technical Services, for AWS at the time, arranged peer reviews to verify
Preface xxiii
the manuscript's technical content. Mrs. Debbie Givens, Publishing Coordinator for
AWS, deserves a note of appreciation for her diligence in arranging reproduction of
th9 many line drawings of figures and graphs.
A bright spot in the lengthy publishing procedure was the engaging of Mr.
Alexander M. Saitta by AWS as Production Editor to handle editing and formatting of
this substantially larger edition of Volume I. Alex, a newcomer to the welding field,
quickly demonstrated ability to fuse his language knowledge with the idiom of weld-
ing technology. In providing assistance on shortening the manuscript, Alex proposed
the inclusion of "Technical Briefs" to avoid deletion of useful fundamental informa-
tion - an effective format measure for which this author is very appreciative.
The Welding Institute, at Abington, England, with which the author was affiliated
for many years as head of its North American Office, was extremely generous with
staff assistance, and provided many photographs and photomicrographs for new illus-
trations. This new edition would have been very difficult to complete without the sup-
port received from TWI.
Hopefully, a revision of Volume I1 will receive similar support from the many col-
leagues and organizations during its preparation, and can be issued in a fourth edition
without undue delay.
George E. Linnert
Hilton Head Island, South Carolina
December, 1994
Contents V
Contents
Chapter One:
Background to Welding Metallurgy. ........................................i. ..
MILESTONES IN WELDING HISTORY ..........................................................1.
THE FUTURE OF WELDING .......................................................................4.. ...
WHAT IS WELDING METALLURGY? ........................................................6.. ...
PUTTING WELDING METALLURGY TO USE ...........................................1.2..
WELDING TECHNOLOGY RESOURCES ..................................................1..2.
Chapter Two:
The Structure sf Metals. ................................................................... 18
ATOMS .........................................................................................................1.8..
Elementary Particles .................................................................................2.0.
Electrons ............................................................................................2..2.. .
Positrons ............................................................................................2..6.. .
Atomic Nuclei ..........................................................................................2..6..
Protons .............................................................................................2..7.. ...
Neutrons. ...........................................................................................2.8.. ...
Atom Construction ......................................................................................3. 2
Isotopes of Elements ...........................................................................3..3.
Isobars ..............................................................................................3..4.. ..
Atomic Weight ..................................................................................3..4.. ...
Atomic Mass ....................................................................................3..4.. ...
Atom Valency ....................................................................................3..5. ...
Ionization. ............................................................................................3..6..
Radioactivity. ........................................................................................3...7
Atom Size or Diameter .......................................................................... 38
THE ELEMENTS ......................................................................................3..9.. ...
AGGREGATES OF ATOMS .....................................................................4..1. ...
The Solid State .....................................................................................4..5. ....
The Crystalline Solids .......................................................................4..5.. ..
Amorphous Solids .................................................................................4..7
The Liquid State .......................................................................................4..8.
The Gaseous State ...................................................................................4..9
FUNDAMENTALS OF CRYSTALS ............................................................5..0..
Identification of Planes and Directions in Crystals ....................................5.6.
Basic Types of Crystals ...........................................................................5..6..
vi Welding Metallurgy
Inert Gas Crystals .................................................................................5..8
Ionic Crystals ..................................................................................... 58
Covalent Crystals ..................................................................................5..9
Metallic Crystals ....................................................................................5..9
THE CRYSTALLINE STRUCTURE OF METALS ........................................... 61
How Does a Crystal Grow from the Melt? .................................................. 64
The Formation of Dendrites .......................................................................6. 6
The Formation of Grains .............................. .. ........................................6. 8
The Shape of Grains ..............................................................................7. 1
The Size of Grains .................................................................................. 72
Undercooling ............................................................................................. 72
THE IMPORTANCE OF A CRYSTALLINE STRUCTURE .............................7 4
Allotropic Transformation ..........................................................................7 5
Solubility in the Solid State ........................................................................7. 6
Plasticity in Metallic Crystals ....................................................................... 77
Slip in Crystalline Structures ................................................................... 77
Slip and Lattice Orientation ..................................................................... 78
Slip in Polycrystalline Metals .................................................................7. 9
Observing Slip. ................ . .............................................................. 80
Twinning in Crystalline Structures .........................................................8. 1
Lattice Imperfections: Dislocations. ............................................................8. 4
Point Defects ........................................................................................ 85
Edge Dislocations .................................................................................8..6
Screw Dislocations ................................................................................. 88
Stacking Faults ..................................................................................... 88
Other Lattice Imperfections ..................................................................... 88
Cold-Working Metals ................................................................................... 88
EXAMINATION OF METAL STRUCTURES ..................................................9 1
Fracture Appearance Assessment ............................................................9..2
Metallography. ........................................................................................9..2.. .
Metallography Using Optical Microscopy. ..............................................9. 2
Quantitative Metallography ................................................................... 105
Metallography Using the Electron Microscope ...................................... 106
Metallography Using Ion Microscopy .................................................... 115
Tunnel-Effect Microscopy ..................................................................... 116
Chemical Analysis of Microstructural Constituents .............................1..1. 6
Newer Techniques in Metallurgy .............................................................1..2 1
FRACTOGRAPHY .....................................................................................1..2. 3
Chapter Three:
The Properties of Metals ................................................................ 133
STRUCTURE SENSITIVITY OF PROPERTIES ........................................... 133
DlRECTlONALlTY IN PROPERTIES. ...........................................................1 35
Contents vii
MECHANICAL PROPERTIES ................................................................... 136
Elastic Behavior of Metals. ......................................................................1..3 7
Young's Modulus of Elasticity .............................................................1 39
Poisson's Ratio ..................................................................................1..3. 9
Limits of Elasticity and Proportionality ................................................1..4 1
Plastic Yielding in Metals .......................................................................1.4..2
Yield Strength ....................................................................................... 343
Breaking Strength of Metals ....................................................................1.4. 3
Tensile Strength ....................................................................................1 44
True Stress and True Strain .................................................................1 44
Notched Tensile Strength .................................................................... 147
Ductility .................................................................................................... 147
.-
Elongation .........................................................................................1..4..8
Reduction of Area ..............................................................................1..4. 9
Ductility Indications from Special Tests ...............................................1. 49
Hardness ................................................................................................... 149
Static Indentation Hardness Testing ..................................................5. 0
Microhardness Testing ......................................................................1..5..1
Dynamic Hardness Testing ............................................................... . . .5 2
Scratch Hardness Testing. ................................................................1..5..3
Conversion of Hardness Numbers ...................................................... 153
Toughness ..............................................................................................5 4
Introduction of Impact Testing .............................................................. 155
FRACTURE IN METALS ...........................................................................1..5. 6
Ductile Fracture .....................................................................................1..5..8
Brittle Fracture. .......................................................................................... 159
Intergranular Fracture. ...........................................................................1..6.2.
Conditions Affecting Fracture Toughness ................................................1. 64
Effect of Temperature ....................................................................... 6 4
Effect of Stress Axiality .....................................................................1 66
Stress Gradient ..................................................................................1..6. 9
Stress Multiaxiality ................................................................................ 170
Effect of Rate of Strain ......................................................................1..7..1
Effect of Cyclic Stress (Fatigue). ...........................................................1..7..4
Fatigue Crack Initiation .........................................................................1 76
Fatigue Crack Propagation ..............................................................1. 76
Fatigue Crack Failure. ........................................................................1..7. 6
Cyclic Stress Limits to Avoid Fatigue Failure .................................... 181
Cyclic Stress Conditions ...................................................................1..8..3
Variable Loading and Cumulative Fatigue Damage ............................1..8 5
FRACTURE MECHANICS: ASSESSMENT OF FRACTURE
TOUGHNESS ................................................................................................ 8 8
Brittle Fracture Test Parameters. ............................................................. 9 0
Section Dimensions .............................................................................1.9..2
P!otting Coordinates ..........................................................................9...2..
Crack Surface Displacement Mode ......................................................1..9 3
Plane-Strain ...................................................................................1..9. 5
viii Welding Metallurgy
Plane-Stress .......................................................................................1.9..5.
Stress Distribution. ................................................................................1..9 6
Procedures for Evaluating Propensity for Brittle Fracture ..........................1 97
Use of Linear-Elastic Fracture Mechanics. ............................................. 198
Development of Elastic-Plastic Fracture Mechanics .................................. 201
Crack Tip Opening Displacement Testing .............................................. 205
The J-Integral Test Method .................................................................... 211
Fatigue Cracking Assessment by Fracture Mechanics ............................. 215
Mechanical Properties at Low Temperature .............................................2..1 8
..
Strength at Low Temperature ........................... 2 9
Impact Toughness at Low Temperature ..............................................2..2 0
Test Methods for Toughness Evaluation. ............................................... 226
Correlation of Results from Fracture Toughness Tests ......................... 236
Improved Mechanical Properties for Low-Temperature Service ................ 238
Mechanical Properties at Elevated and High Temperatures .....................2. 38
Short-Time Elevated Temperature Testing ...........................................2. 41
Long-Time Elevated Temperature Testing ............................................2. 42
Mechanical Properties After Plastic Work .................................................2..4 7
Hot Work ............................................................................................2..4..8.
Cold Work ............................................................................................... 248
Peening ................................................................................................... 248
Irradiation ................................................................................................ 249
PHYSICAL PROPERTIES ...........................................................................2..5. 8
Density ..................................................................................................2..5..8..
Thermal Properties. .................................................................................2..5..9
Specific Heat .....................................................................................2..6..0..
Thermal Conductivity ...........................................................................2..6. 1
Melting Point or Melting Range .............................................................. 264
Heat of Fusion ........................................................................................ 264
Viscosity and Surface Tension of Molten Metals ................................... 264
Boiling Point and Heat of Vaporization. ..................... ..... ........................2 66
Thermal Expansion and Contraction ..................................................... 266
Thermionic Work Function ..................................................................2.6..8.
Electrical Properties ................................................................................2..6..8
Magnetic Properties .................................................................................. 270
Evaluation of Magnetization ................................................................... 272
Summary of Magnetic Behavior ............................................................. 273
Involvement of Magnetization in Welding ............................................... 274
CHEMICAL PROPERTIES ..........................................................................2..7. 4
Corrosion of Metals .................................................................................2..7..5
Corrosion in Aqueous Solutions ..........................................................2..7. 6
Corrosion in Hot Gases .......................................................................2..8. 2
Corrosion in Molten Metals ...................................................................2..8 2
Corrosion in Molten Salt .........................................................................2 83
Forms of Corrosion Pertinent to Weldments .............................................. 283
Stress Corrosion Cracking (SCC) .......................................................... 284