Effect of heating rate and holding temperature on quenching microstructure and properties of NM400 steel
The heating and cooling processes of induction heat treatment of NM400 hot rolled strip steel were simulated using DIL805A phase change dilatometer.The effect of heating rate and holding temperature on the original austenite grain size,microstructure characteristics and hardness of the experimental steel was studied.The results show that the heating rate has a significant impact on the original austenite grain size of the experimental steel.As the heating rate increases,the original austenite grain size gradually decreases.At a rapid heating rate of 80℃/s,the original austenite grain size is about 26.6 μm,the quenched martensite packet is obviously refined,and the hardness is 413.9 HV.The holding temperature has a significant impact on the undercooling during the cooling.As the holding temperature increases,the undercooling increases,and the martensite content gradually increases after quenching.When the holding temperature rises to 1010℃,the microstructure of the quenched experimental steel is martensite,with a hardness of 409.3 HV.
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