4Cr3Mn1Mo2V新型热作模具钢的连续冷却转变行为

Continuous Cooling Transformation Behavior of 4Cr3Mn1Mo2V New Hot Work Die Steel

通过热膨胀仪测定了4Cr3Mn1Mo2V钢不同冷却速率下的热膨胀曲线,结合光学显微镜、扫描电镜及显微硬度计,得到该钢的相变点和奥氏体连续冷却转变(CCT)曲线,利用局部平衡配分模型分析了锰元素对该钢连续冷却转变行为的影响。结果表明:4Cr3Mn1Mo2V钢加热时珠光体向奥氏体转变的开始温度Ac1、加热时二次渗碳体全部溶入奥氏体的终了温度Accm、马氏体转变开始温度Ms分别为806,870,300℃;随着冷却速率的降低,组织由马氏体转变为贝氏体,同时钢的硬度降低;贝氏体转变临界冷却速率为02.℃·s^(-1);CCT曲线中只存在马氏体和贝氏体转变区,这与锰元素会影响碳原子的扩散有关。

The thermal expansion curve of 4Cr3Mn1Mo2Vsteel at different cooling rates was measured by a thermal dilatometer,and combined with optical microscope,scanning electron microscope and micro hardness tester,the phase change point and the continuous cooling transformation(CCT)curve of austenite of the steel were obtained.The influence of manganese element on the continuous cooling transformation behavior of the steel was analyzed by a local equilibrium distribution model.The results show that the initial temperature of pearlite transforming to austenite during heating(Ac1),the final temperature of secondary cementite dissolving into austenite during heating(Accm)and the initial temperature of martensite transformation(Ms)were 806,870,300℃,respectively.With increasing cooling rate,the microstructure was changed from martensite to bainite,and the hardnss of the steel decreased.The critical cooling rate of bainite transformation was 0.2℃·s^(-1).Only martensite and bainite transformation zone were observed in the CCT curve,which was related to the effect of manganese element on the diffusion of carbon atoms.