Thermomechanical Processing of High-Strength Low-Alloy Steels

Thermomechanical Processing of High-Strength Low-Alloy Steels considers some advanced techniques and metallurgical bases for controlled-rolling. This book contains 12 chapters. In Chapter 1, the purpose of thermomechanical processing and historical survey is described, while in Chapter 2, the kinetics of phase transformations and refinement of grain size in steels are elaborated. The techniques and metallurgical bases for controlled-rolling in the recrystallization, non-recrystallization, and (? + y) regions are reviewed in Chapters 3 to 5. Chapters 6 and 7 discuss the deformation resistance during hot-rolling and restoration processes. The phase transformations during cooling following hot-rolling are mentioned in Chapter 8, followed by a summarization of the effects of alloying elements in Chapter 9. Chapters 10 and 11 deal with the mechanical properties of controlled-rolled steel and prediction and control of microstructure and properties by thermomechanical processes. The problems faced and possibilities for future developments are stated in the last chapter. This publication is recommended for physicists, metallurgists, and researchers concerned with controlled-rolling, including non-specialists who have some knowledge of metallurgy.

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.