Welding Metallurgy of Stainless Steels

When considering the operational performance of stainless steel weldments the most important points to consider are corrosion resistance, weld metal mechanical properties and the integrity ofthe weldedjoint. Mechanical and corrosion resistance properties are greatly influenced by the metallurgical processes that occur during welding or during heat treatment of welded components. This book is aimed, there fore, at providing information on the metallurgical problems that may be encountered during stainless steel welding. In this way we aim to help overcome a certain degree of insecurity that is often encountered in welding shops engaged in the welding of stainless steels and is often the cause of welding problems which may in some instances lead to the premature failure of the welded component. The metallurgical processes that occur during the welding of stainless steel are of a highly intricate nature. The present book focuses in particular on the signif icance of constitution diagrams, on the processes occurring during the solidification of weld metal and on the recrystallization and precipitation phenomena which take place in the area of the welds. There are specific chapters covering the hot cracking resistance during welding and the practical welding of a number of different stainless steel grades. In addition, recommendations are given as to the most suitable procedures to be followed in order to obtain maximum corrosion resistance and mechanical properties from the weldments.

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When welding stainless steels, metallurgical reactions take place which greatly influence corrosion resistance and mechanical properties. The book deals with this subject by discussing constitution diagrams, solidification and segregation phenomenas, phase transformations, precipitations of carbides and intermetallic phases, and cracking problems. In addition, directions for welding techniques are given to avoid failures in practical welding operations.

Contenu
1 Significance of Constitution Diagrams for the Understanding of Welding Phenomena.- 1.1 Iron-Chromium, Iron-Nickel and Chromium-Nickel Constitution Diagrams.- 1.2 The Ternary Iron-Chromium-Nickel Constitution Diagram.- 1.2.1 Solidification and Crystallization Phenomena of Iron-Chromium- Nickel Steel Alloys.- 1.2.2 Phenomena During Cooling from the End of Solidification to Ambient Temperature.- 1.3 Influence of Other Elements on the Iron-Chromium-Nickel Constitution Diagram.- 1.3.1 Influence of Carbon.- 1.3.2 Influence of Nitrogen.- 1.3.3 Influence of Molybdenum.- 1.3.4 Influence of Manganese.- 1.3.5 Influence of Niobium.- 1.3.6 Influence of Titanium.- 1.3.7 Influence of Silicon.- 1.3.8 Influence of Sulphur.- 1.3.9 Influence of Phosphorus.- 1.3.10 Influence of Copper.- 1.3.11 Influence of Boron.- 1.3.12 Influence of Oxygen.- 1.3.13 Influence of Hydrogen.- 2 Metallurgical Processes Occurring During Solidification and Cooling in Stainless Steel Weld Metal.- 2.1 Primary Crystallization of Weld Pools.- 2.2 Primary Crystallization of Binary and Ternary Systems.- 2.3 Phenomena at the Liquid-Solid Interface (Solidification Front).- 2.4 Crystal Growth During Solidification and Crystal Configurations.- 2.5 Primary Crystallization of Stainless Steel Weld Metals.- 2.6 Cooling Rate and Thermal Supercooling During Solidification of Stainless Steel Weld Metal.- 2.7 Segregations in Stainless Steel Weld Metal During Solidification.- 3 Metallurgical Phenomena in Secondary Crystallization of Stainless Steels and Weld Metals.- 3.1 Recrystallization of Weld Metal.- 3.2 ?-? Transformation of Stainless Steel Weld Metal.- 3.3 Schaeffler Diagram, Ferrite Measurement, DeLong Diagram.- 3.4 ?-? Transformation of Stainless Steel Alloys.- 3.4.1 Transformation in the Pearlite Range.- 3.4.2 Transformation in the Martensite Range.- 3.4.3 Formation of Stable Austenite During Tempering.- 4 Precipitation Phenomena in Stainless Steels and Weld Metals.- 4.1 Carbide Precipitations in Stainless Steels with Special Consideration to Intergranular Corrosion.- 4.1.1 Influence of the Type of Structure on the Tendency Towards Carbide Precipitation in Stainless Steels.- 4.1.2 Influence of Alloying Elements on. Carbide Precipitation and Intergranular Corrosion (IC) in Austenitic Stainless Chromium-Nickel Steels.- 4.1.2.1 Influence of Carbon and Nickel.- 4.1.2.2 Influence of Silicon.- 4.1.2.3 Influence of Chromium.- 4.1.2.4 Influence of Nitrogen.- 4.1.2.5 Influence of Molybdenum.- 4.1.2.6 Influence of Titanium and Niobium.- 4.1.2.7 Influence of Manganese.- 4.1.3 Carbide Precipitation in Ferritic, Low Carbon Martensitic and Austenitic-Ferritic (Duplex) Steels.- 4.1.3.1 Ferritic Stainless Chromium Steels.- 4.1.3.2 Low Carbon Cr-Ni Martensitic Stainless Steels (Soft Martensitic Steels).- 4.1.3.3 Austenitic-Ferritic (Duplex) Steels with Low Carbon Contents.- 4.1.4 Carbide Precipitations in Stainless Steel Weld Metal and in the Heat Affected Zone (HAZ).- 4.1.4.1 Knife Line Corrosion in Weldments Made from Stabilized Austenitic Stainless Steels after Heat Treatment in the Temperature Range of 500700° C.- 4.1.4.2 Increased Intergranular Corrosion in Weld Metal Due to Segregations and Phase Separations.- 4.1.4.3 Ferrite Track Corrosion in Austenitic Weld Metal.- 4.2 The Precipitation of Intermetallic Phases in Stainless Steels and Weld Metals.- 4.2.1 The Precipitation of Sigma Phase in Austenitic Stainless Steels and Weld Metals.- 4.2.2 The Precipitation of Sigma Phase in Ferritic and Austenitic-Ferritic Stainless Steels.- 4.2.3 The Precipitation of Sigma Phase in Austenitic, Austenitic-Ferritic and Ferritic Stainless Steel Weld Metals.- 4.2.4 The Precipitation of Intermetallic Phases in Chromium-Nickel- Molybdenum Stainless Steels and Weld Metals.- 4.3 475° C Embrittlement in Stainless Steels and Stainless Steel Weld Metals.- 5 Hot Cracking Resistance During the Welding of Austenitic Stainless Steels.- 5.1 Formation of Hot Cracks.- 5.1.1 Formation Mechanics of Solidification Cracks.- 5.1.2 Formation Mechanics of Liquation Cracks.- 5.2 Hot Cracking Tests.- 5.2.1 Hot Cracking Tests for the Determination of the Critical Deformation Rate in the Welding Zone.- 5.2.2 The Program Controlled Deformation Cracking Test (PVR Test).- 5.3 Criteria which Influence the Hot Cracking Susceptibility of Austenitic Stainless Steel Weldments.- 5.3.1 Influence of Primary Solidification on the Hot Cracking Behaviour of Austenitic Stainless Steel Weld Metal.- 5.3.2 Influence of the Residual Delta Ferrite Content on the Hot Cracking Behaviour.- 5.3.3 Influence of Alloying Elements and Impurities which Promote Hot Cracking.- 5.3.4 Hot Cracking Sensitivity of Fully Austenitic Weld Metal.- 5.3.5 Influence of Welding Parameters and Material Thickness on the Hot Cracking Sensitivity of Austenitic Stainless Steel Weldments.- 6 Welding Metallurgy of Ferritic Stainless Chromium Steels with Carbon Contents Below 0.15%.- 6.1 Practical Welding of Stainless Chromium Steels.- 6.2 Mechanical Properties of Stainless Steel Weld Metals with 12 and 17% Chromium.- 6.3 Precipitation Phenomena in Ferritic Stainless Chromium Steels and Weld Metals.- 7 Welding Metallurgy of Low Carbon Chromium-Nickel Martensitic Stainless Steels (Soft Martensitic Steels).- 7.1 Practical Welding of Low Carbon Martensitic Stainless Steels.- 7.2 Mechanical Properties of Low Carbon Martensitic Stainless Steel Weld Metal.- 7.3 Precipitation Phenomena in Low Carbon Soft Martensitic Stainless Steels and Weld Metals.- 8 Welding Metallurgy of Duplex Austenitic-Ferritic Stainless Steels.- 8.1 Practical Welding of Duplex Austenitic-Ferritic Stainless Steels.- 8.2 Mechanical Properties of Duplex Austenitic-Ferritic Stainless Steel Weld Metal.- 8.3 Precipitation Phenomena in Duplex Austenitic-Ferritic Stainless Steels and Weld Metals.- 9 Welding Metallurgy of Austenitic Stainless Steels.- 9.1 Welding Metallurgy of Unstabilized Austenitic Stainless Steels.- 9.1.1 Practical Welding of Unstabilized Austenitic…