Effect of austenitic state on microstructure and mechanical properties of martensite/bainite steel

Various heat treatments and thermal simulation with different austenitizing temperatures and austenite deformation were applied on a bearing steel to obtain various austenitic state. The effect of austenitic state on microstructure of martensite/bainite (M/B) dual phase steel and its mechanical property has been investigated via microstructure observation and kinetic analysis. The results show that the M/B steels austenitized at 900 and 950 degrees C have better comprehensive performance compared with the steels austenitized at 850 and 1050 degrees C. The refined microstructure can be obtained after deformation, and the heavy deformation and low deformation temperature are useful for refining the microstructure. The bainite lath is longer and has well-directional arrangement at high austenitizing temperature with the same deformation. Furthermore, austenite deformation can improve the nucleation ratio, reduce incubation process, and affect the kinetics of bainite transformation significantly.