Welding Metallurgy and Weldability of Stainless Steels

JOHN C. LIPPOLD, PhD, is a professor in the Welding Engineering Program at The Ohio State University and leader of the Welding and Joining Metallurgy Group. A Fellow of both the American Welding Society and ASM International, Dr. Lippold has received numerous awards, including the Charles H. Jennings Memorial Award, the William Spraragen Memorial Award, the Warren F. Savage Memorial Award, the McKay-Helm Award, the A.F. Davis Silver Medal, the James F. Lincoln Gold Medal, the William Irrgang Memorial Award, and the Dr. Comfort A. Adams Lecture Award. DAMIAN J. KOTECKI, PhD, is Technical Director for Stainless and High-Alloy Product Development at Lincoln Electric and Vice President and Fellow of the American Welding Society. His many industry awards include the James F. Lincoln Gold Medal, the William Irrgang Memorial Award, the R.D. Thomas Memorial Award, the R.D. Thomas, Jr. International Lecture Award, the Dr. Comfort A. Adams Lecture Award, and the IIW Thomas Medal.

• PREFACE xv1 INTRODUCTION 11.1 Definition of a Stainless Steel 21.2 History of Stainless Steel 21.3 Types of Stainless Steel and Their Application 41.4 Corrosion Resistance 51.5 Production of Stainless Steel 6References 72 PHASE DIAGRAMS 82.1 Iron–Chromium System 92.2 Iron–Chromium–Carbon System 102.3 Iron–Chromium–Nickel System 122.4 Phase Diagrams for Specific Alloy Systems 15References 183 ALLOYING ELEMENTS AND CONSTITUTION DIAGRAMS 193.1 Alloying Elements in Stainless Steels 193.1.1 Chromium 203.1.2 Nickel 203.1.3 Manganese 213.1.4 Silicon 213.1.5 Molybdenum 223.1.6 Carbide-Forming Elements 223.1.7 Precipitation-Hardening Elements 233.1.8 Interstitial Elements: Carbon and Nitrogen 233.1.9 Other Elements 243.2 Ferrite-Promoting Versus Austenite-Promoting Elements 243.3 Constitution Diagrams 253.3.1 Austenitic–Ferritic Alloy Systems: Early Diagrams and Equivalency Relationships 253.3.2 Schaeffler Diagram 293.3.3 DeLong Diagram 333.3.4 Other Diagrams 343.3.5 WRC-1988 and WRC-1992 Diagrams 403.4 Austenitic–Martensitic Alloy Systems 433.5 Ferritic–Martensitic Alloy Systems 463.6 Neural Network Ferrite Prediction 50References 524 MARTENSITIC STAINLESS STEELS 564.1 Standard Alloys and Consumables 574.2 Physical and Mechanical Metallurgy 594.3 Welding Metallurgy 634.3.1 Fusion Zone 634.3.2 Heat-Affected Zone 674.3.3 Phase Transformations 704.3.4 Postweld Heat Treatment 714.3.5 Preheat, Interpass, and Postweld Heat Treatment Guidelines 744.4 Mechanical Properties of Weldments 774.5 Weldability 774.5.1 Solidification and Liquation Cracking 784.5.2 Reheat Cracking 784.5.3 Hydrogen-Induced Cracking 794.6 Supermartensitic Stainless Steels 804.7 Case Study: Calculation of MS Temperatures of Martensitic Stainless Steels 84References 865 FERRITIC STAINLESS STEELS 875.1 Standard Alloys and Consumables 885.2 Physical and Mechanical Metallurgy 925.2.1 Effect of Alloying Additions on Microstructure 955.2.2 Effect of Martensite 955.2.3 Embrittlement Phenomena 965.2.3.1 475°C Embrittlement 975.2.3.2 Sigma and Chi Phase Embrittlement 975.2.3.3 High-Temperature Embrittlement 985.2.3.4 Notch Sensitivity 1035.2.4 Mechanical Properties 1045.3 Welding Metallurgy 1045.3.1 Fusion Zone 1045.3.1.1 Solidification and Transformation Sequence 1045.3.1.2 Precipitation Behavior 1095.3.1.3 Microstructure Prediction 1115.3.2 Heat-Affected Zone 1125.3.3 Solid-State Welds 1135.4 Mechanical Properties of Weldments 1145.4.1 Low-Chromium Alloys 1145.4.2 Medium-Chromium Alloys 1165.4.3 High-Chromium Alloys 1195.5 Weldability 1235.5.1 Weld Solidification Cracking 1235.5.2 High-Temperature Embrittlement 1245.5.3 Hydrogen-Induced Cracking 1265.6 Corrosion Resistance 1265.7 Postweld Heat Treatment 1305.8 Filler Metal Selection 1325.9 Case Study: HAZ Cracking in Type 436 During Cold Deformation 1325.10 Case Study: Intergranular Stress Corrosion Cracking in the HAZ of Type 430 135References 1376 AUSTENITIC STAINLESS STEELS 1416.1 Standard Alloys and Consumables 1436.2 Physical and Mechanical Metallurgy 1476.2.1 Mechanical Properties 1496.3 Welding Metallurgy 1516.3.1 Fusion Zone Microstructure Evolution 1536.3.1.1 Type A: Fully Austenitic Solidification 1546.3.1.2 Type AF Solidification 1556.3.1.3 Type FA Solidification 1556.3.1.4 Type F Solidification 1586.3.2 Interfaces in Single-Phase Austenitic Weld Metal 1626.3.2.1 Solidification Subgrain Boundaries 1626.3.2.2 Solidification Grain Boundaries 1636.3.2.3 Migrated Grain Boundaries 1636.3.3 Heat-Affected Zone 1646.3.3.1 Grain Growth 1656.3.3.2 Ferrite Formation 1656.3.3.3 Precipitation 1656.3.3.4 Grain Boundary Liquation 1666.3.4 Preheat and Interpass Temperature and Postweld Heat Treatment 1666.3.4.1 Intermediate-Temperature Embrittlement 1676.4 Mechanical Properties of Weldments 1686.5 Weldability 1736.5.1 Weld Solidification Cracking 1736.5.1.1 Beneficial Effects of Primary Ferrite Solidification 1756.5.1.2 Use of Predictive Diagrams 1776.5.1.3 Effect of Impurity Elements 1796.5.1.4 Ferrite Measurement 1816.5.1.5 Effect of Rapid Solidification 1826.5.1.6 Solidification Cracking Fracture Morphology 1866.5.1.7 Preventing Weld Solidification Cracking 1896.5.2 HAZ Liquation Cracking 1896.5.3 Weld Metal Liquation Cracking 1906.5.4 Ductility-Dip Cracking 1946.5.5 Reheat Cracking 1966.5.6 Copper Contamination Cracking 1996.5.7 Zinc Contamination Cracking 2006.5.8 Helium-Induced Cracking 2006.6 Corrosion Resistance 2006.6.1 Intergranular Corrosion 2016.6.1.1 Preventing Sensitization 2046.6.1.2 Knifeline Attack 2056.6.1.3 Low-Temperature Sensitization 2056.6.2 Stress Corrosion Cracking 2066.6.3 Pitting and Crevice Corrosion 2086.6.4 Microbiologically Induced Corrosion 2086.6.5 Selective Ferrite Attack 2096.7 Specialty Alloys 2116.7.1 Heat-Resistant Alloys 2116.7.2 High-Nitrogen Alloys 2146.8 Case Study: Selecting the Right Filler Metal 2206.9 Case Study: What’s Wrong with My Swimming Pool? 2236.10 Case Study: Cracking in the Heat-Affected Zone 224References 2257 DUPLEX STAINLESS STEELS 2307.1 Standard Alloys and Consumables 2317.2 Physical Metallurgy 2347.2.1 Austenite–Ferrite Phase Balance 2347.2.2 Precipitation Reactions 2377.3 Mechanical Properties 2377.4 Welding Metallurgy 2387.4.1 Solidification Behavior 2387.4.2 Role of Nitrogen 2407.4.3 Secondary Austenite 2447.4.4 Heat-Affected Zone 2467.5 Controlling the Ferrite–Austenite Balance 2507.5.1 Heat Input 2517.5.2 Cooling Rate Effects 2517.5.3 Ferrite Prediction and Measurement 2537.6 Weldability 2547.6.1 Weld Solidification Cracking 2547.6.2 Hydrogen-Induced Cracking 2547.6.3 Intermediate-Temperature Enbrittlement 2557.6.3.1 Alpha-Prime Embrittlement 2567.6.3.2 Sigma Phase Embrittlement 2567.7 Weld Mechanical Properties 2597.8 Corrosion Resistance 2617.8.1 Stress Corrosion Cracking 2617.8.2 Pitting Corrosion 261References 2628 PRECIPITATION-HARDENING STAINLESS STEELS 2648.1 Standard Alloys and Consumables 2658.2 Physical and Mechanical Metallurgy 2678.2.1 Martensitic Precipitation-Hardening Stainless Steels 2698.2.2 Semi-Austenitic Precipitation-Hardening Stainless Steels 2748.2.3 Austenitic Precipitation-Hardening Stainless Steels 2768.3 Welding Metallurgy 2778.3.1 Microstructure Evolution 2788.3.2 Postweld Heat Treatment 2788.4 Mechanical Properties of Weldments 2798.5 Weldability 2808.6 Corrosion Resistance 285References 2859 DISSIMILAR WELDING OF STAINLESS STEELS 2879.1 Applications of Dissimilar Welds 2879.2 Carbon or Low-Alloy Steel to Austenitic Stainless Steel 2889.2.1 Determining Weld Metal Constitution 2889.2.2 Fusion Boundary Transition Region 2919.2.3 Nature of Type II Boundaries 2949.3 Weldability 2969.3.1 Solidification Cracking 2969.3.2 Clad Disbonding 2989.3.3 Creep Failure in the HAZ of Carbon or Low-Alloy Steel 2999.4 Other Dissimilar Combinations 3019.4.1 Nominally Austenitic Alloys Whose Melted Zone Is Expected to Include Some Ferrite or to Solidify asPrimary Ferrite 3019.4.2 Nominally Austenitic Alloys Whose Melted Zone Is Expected to Contain Some Ferrite, Welded to FullyAustenitic Stainless Steel 3019.4.3 Austenitic Stainless Steel Joined to Duplex Stainless Steel 3029.4.4 Austenitic Stainless Steel Joined to Ferritic Stainless Steel 3029.4.5 Austenitic Stainless Steel Joined to Martensitic Stainless Steel 3029.4.6 Martensitic Stainless Steel Joined to Ferritic Stainless Steel 3029.4.7 Stainless Steel Filler Metal for Difficult-to-Weld Steels 3039.4.8 Copper-Base Alloys Joined to Stainless Steels 3059.4.9 Nickel-Base Alloys Joined to Stainless Steels 306References 30710 WELDABILITY TESTING 30910.1 Introduction 30910.1.1 Weldability Test Approaches 31010.1.2 Weldability Test Techniques 31010.2 Varestraint Test 31110.2.1 Technique for Quantifying Weld Solidification Cracking 31210.2.2 Technique for Quantifying HAZ Liquation Cracking 31610.3 Hot Ductility Test 31910.4 Fissure Bend Test 32310.5 Strain-to-Fracture Test 32810.6 Other Weldability Tests 329References 329APPENDIX 1 NOMINAL COMPOSITIONS OF STAINLESS STEELS 331APPENDIX 2 ETCHING TECHNIQUES FOR STAINLESS STEEL WELDS 343AUTHOR INDEX 347SUBJECT INDEX 353

"…offers a solid and detailed coverage of welding with stainless steels." (E-STREAMS, August 2006) "…an exciting metallurgy book…that is difficult to put down…the authors have performed an excellent piece of work in developing this book." (Materials and Manufacturing Processes, February 2006)"...a delight to read...has a wealth of information and written in a concise, informative manner…" (MRS Bulletin, January 2006)"...an authoritative resource for both students and professionals that serves as a handy reference...essential." (CHOICE, December 2005)"…information is not something that can be easily found in most metallurgical reference books…extremely useful for the selection or application of stainless steels." (Journal of Metals Online, July 21, 2005)"...an up-to-date textbook that will surely become a respected volume for years to come." (Welding Journal, September 2005)