Ultra-Fine Grained Steels discusses results of the New Generation Iron and Steel ,Materials research project funded over the last ten years. Modern sustainability requirements want that iron and steel must meet tour conditions:stronger, longer service life, leading-edge manufacturing technology (low cost, material and energy efficient), and environmentally sound (waste recycling, reduced carbon dioxide emission). Therefore, new generation iron and steel materials featuring "double strength and double service life" are needed (labeled "ultra steels" in Japan).

1 Overview

 1.1 The Technology of Controlled Rolling and Controlled Cooling

 1.2 g & D Program of "Super Steels" and "New Generation Steel Materials"

 1.3 The Formation of Ultra-fine Grains and Microstructural Refinement of Steels-Core Technique for the R & D of New Generation Steel Materials

 1.4 Theory and Technology on Ultra-fine Grains

1.4.1 The state change and microstructure refinement of austenite during hot deformation

1.4.2 Deformation induced ferrite transformation

 1.4.2.1 Thermodynamic consideration of deformation induced ferrite transformation

 1.4.2.2 DIFT phase transformation and characters of transformed products

1.4.3 Deformation induced precipitation and medium temperature phase transformation control

1.4.4 The influence of nanometer size precipitates on ultra fine grain steel

1.4.5 Ultra grain refinement of alloy structural steels and the way of increasing the resistance against delayed fracturing

1.4.6 The development of carbide-free bainite/martensite multiple phase steels

 1.5 Several Key Technologies Concerning the Development of Ultra Fine Grain Steels

1.5.1 Steel cleanness

1.5.2 Refinement and homogenization of solidification structure

1.5.3 Brief introduction of welding technique and economy of ultra fine grain steels

 References

2 Refinement of Austenitie Microstrueture and Its Influence on γα→ Transformation

 2.1 Thermomechanical Control Process and Refinement of Austenitic Microstructure

2.1.1 Rolling at the austenite-recrystallization temperature region (RARTR)

 2.1.1.1 Metadynamic recrystallization

 2.1.1.2 Static recrystallization

2.1.2 Rolling in austenite non-recrystallization temperature region

2.1.3 Rolling at the under-cooled austenite

2.1.4 Accelerated cooling and microstructural refinement

 2.2 Influence of Austenitic Recrystallization on Subsequently Transformed Grain Size

2.2.1 Influence of recrystallized or deformed austenite on ferrite transformation

 2.2.1.1 Influence of recrystallized austenite on ferrite transformation

 2.2.1.2 Influence of partially recrystallized austenite on ferrite transformation

 2.2.1.3 Influence of non-recrystallized austenite on ferrite transformation

2.2.2 Influence of recrystallization in the austenite on DIFT

  References

3 Deformation Induced Ferrite Transformation

 3.1 Introduction

 3.2 Experimental Confirmation and Study Method of DIFT

3.2.1 Microstructure observation on the quenched sample

3.2.2 Mechanical behavior measurement

3.2.3 Dilatometry measurement

3.2.4 In-situ X-ray diffraction

 3.3 Thermodynamics of DIFT

3.3.1 Deformation stored energy

3.3.2 Transformation driving force

3.3.3 Ad3 versus deformation stored energy

 3.4 Kinetics of DIFT

3.4.1 Microstructural evolution and nucleation sites

3.4.2 Transformation fraction versus strain

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