Continuous cooling transformation behavior of low-carbon Mn-Cu-Ti-Nb steel

By dilatometric change combined with microstructure and hardness measurement,austenite CCT diagrams for non-predeformation and deformation process for low carbon Mn-Cu-Ti-Nb steel used in the bogie frame of high-speed trains were established by MMS-200 thermal mechanical simulator.The effects of predeformation and cooling rate on γ→α transformation behavior and microstructure were studied.The results show that the ferrite transformation temperature is lowed and the grain size is refined with increasing of cooling rate,and the bainite transformation is also accelerated.On the one hand,the deformation can promote ferrite transformation and refine the ferrite grains,and on the other hand,can restrain bainite transformation and the volume fraction of bainite and hardness are decreased.