Thermomechanical Processing of High-Strength Low-Alloy Steels

Table of Contents:
1 Introduction 1.1 What is Thermomechanical Processing? 1.2 Historical Survey 1.2.1 Controlled Low-Temperature Hot-Rolling Of Ships' Plates 1.2.2 Controlled-Rolling of Low-Carbon Niobium-Containing Steels 1.2.3 Outline of Controlled-Rolling 1.2.4 Further Developments of Controlled-Rolling 1.2.5 Accelerated Cooling in Plate-Rolling Mills References2 Austenite to Ferrite Transformation and Refinement of a Grain Size 2.1 ??a Phase Transformation 2.1.1 Classification of Phase Transformation 2.1.2 Effect of Alloying Elements on ??a Transformation 2.1.3 Precipitation of Alloy Carbide from a 2.2 Transformation Kinetics 2.2.1 Transformation Kinetics of ? (Isothermal) 2.2.2 Continuous Cooling Transformation Kinetics of ? 2.3 a Grain Size Transformed from ? 2.3.1 Major Purpose of Controlled-Rolling 2.3.2 Expression for a Grain Size (Isothermal) 2.3.3 Estimation of a Grain Size Formed by Continuous Cooling Transformation 2.4 Deformation Behaviour of Steels at Elevated Temperatures 2.4.1 Restoration During Hot-Deformation 2.4.2 Static Restoration During Holding Right After Hot-Deformation 2.4.3 Effect of Alloying Elements on the Retardation of Recrystallization 2.4.4 Texture Due to Hot-Deformation 2.5 a Grain Refinement by the Work-Hardening of Austenite 2.5.1 a Nucleation in Deformed ? (Isothermal) 2.5.2 Growth of a in Deformed ? (Isothermal) 2.5.3 a Grain Size Formed from Deformed ? (Isothermal) 2.6 a Grain Refinement by Accelerated Cooling 2.7 Summary References3 Deformation of Austenite in the Recrystallization Region 3.1 Metallurgical Changes During and After Constant-Rate Hot-Deformation 3.2 Dynamic and Metadynamic Recrystallization by Rolling Hot-Deformations 3.3 Temperature-Reduction-Recrystallization 3.4 Controlled-Rolling for Refinement of Recrystallized ? Grains 3.5 Effects of Alloying Elements on Recrystallization Behaviour 3.5.1 Recrystallization Kinetics 3.5.2 Recrystallized Grain Size References4 Deformation of Austenite in the Nonrecrystallization Region 4.1 Retardation of Recrystallization of ? 4.2 Formation and Role of Deformation Bands 4.3 Strain-Induced and/or Strain-Enhanced Transformation References5 Deformation in the (Austenite Plus Ferrite) Two-Phase Region 5.1 Deformation Behaviour in the (?+a) Two-Phase Region 5.2 Anisotropy and Texture 5.3 Separation 5.4 Elimination of Separation References6 Deformation Resistance at Elevated Temperatures 6.1 Strain Hardening and Restoration 6.2 Metallurgical Factors Affecting Hot-Strength 6.3 Hot-Deformation Resistance Formulae References7 Softening Behaviour Immediately After Rolling and Strain Accumulation 7.1 Softening Behaviour Immediately After Hot-Rolling 7.2 Factors Affecting Softening 7.3 Introduction of Strain Accumulation into Deformation and Resistance Formulae 7.4 Computer Simulation for Predicting Mill Load References8 Transformation Behaviours of Austenite After Thermomechanical Treatment 8.1 Transformation from Recrystallized ? 8.2 Transformation from Nonrecrystallized ? References9 Alloying Elements and Impurities 9.1 Microalloying Elements 9.1.1 Solubility Products 9.1.2 Retardation of ? Recrystallization 9.1.3 Grain Refinement and Precipitation Hardening 9.2 Substitutional Alloying Elements 9.3 Impurity Elements References10 Properties of Controlled-Rolled Steels 10.1 Strengthening and Toughening Mechanisms 10.1.1 Interpretation of Mechanical Properties 10.2 Mechanical Properties 10.2.1 High-Tensile Steel with a Tensile Strength Of 50kgf/mm2 (Ht-50 Steel) 10.2.2 Line-Pipe Steels 10.2.3 Acicular a Steel 10.2.4 As-Hot-Rolled Dual-Phase Steel 10.3 Weldability 10.3.1 Susceptibility to Weld Cracking 10.3.2 Toughness at the Heat-Affected Zone References11 Prediction and Control of Microstructural Change and Mechanical Properties in Hot-Rolling 11.1 A Model to Predict Recrystallized ? Grain Size During Hot-Rolling 11.1.1 Dynamic Recrystallization 11.1.2 Static Recrystallization 11.1.3 Statically Recrystallized Grain Size 11.1.4 Grain Growth 11.1.5 Static Recovery 11.1.6 Effective ? Grain Boundary Area for the Formation of a Grains 11.2 Prediction of ? Grain Size in Multipass Rolling 11.3 Strain-Induced Precipitation of Niobium Carbonitrides 11.4 Strain Accumulation in the Low-Temperature ? Region 11.5 Deformation in the (?+a) Two-Phase Region 11.6 Relation Between Microstructure and Strength and Toughness References12 Further Developments in Thermomechanical Processing 12.1 Controlled-Cooling After Controlled-Rolling 12.1.1 Effects of Cooling Variables on Mechanical Properties 12.1.2 Transformed Microstructure and Strengthening Mechanism 12.2 Hot-Charge Rolling and Hot-Direct Rolling References13 ConclusionIndex