Development of the low temperature bainite

Abstract

The possibility of obtaining steels with nano-size plates of bainitic-ferrite by isothermal transformation at low temperature is set forth. These steels have attracted great interest due to their excellent combination of strength, toughness, and ductility. In further investigations, the composition and the processing methods of these steels are adjusted to: (1) Optimize their technological properties with regard to mechanical behavior, weldability and formability. (2) Accelerate their transformation kinetics. (3) Minimize/eliminate the need for expensive alloying elements. (4) Lower the martensite start temperature (Ms) either by thermo-mechanical processing or by modifying the bainite transformation stage. Suppressing Ms is of particular importance in steels with relatively low carbon content; that is to allow for bainite formation at low temperature. Furthermore, many reports addressed some technological aspects like fatigue behavior, wear resistance and bake hardenability. This article presents an overview of the so far studied alloying strategies and processing methods adopted for developing the low temperature bainite together with addressing some examined technological themes. The paper is engrafted in relevant sections with new results of the authors that are not published before. One of these results is that the low temperature bainite possesses a very strong bake hardening potential.