22MnB5热变形行为研究及本构方程建立

Study on Hot Deformation Behavior and Flow Stress Constitutive Model of 22MnB5 at High Temperature

摘要：以22MnB5为实验材料，在500～950℃范围内和应变速率为0．01S、0．1S-1、1s-1的实验条件下，采用热模拟机Gleeble-1500对硼钢进行热拉伸实验，研究了不同变形条件下硼钢的热流变行为；对拉断后的试样断面进行组织分析，阐述了不同变形条件下硼钢的组织对热流变行为变化的影响。研究表明：硼钢的热变形行为属于典型的动态回复型，其流动应力随着温度的升高而减小，随着应变速率的增大而增大，且温度对流动应力的影响更显著；在500℃、应变速率0．01S。的条件下，硼钢高温下的热力学行为与上述规律有所差别，其流变应力高于高应变速率下的流变应力。最后根据高温拉伸实验所得数据，构建了22MnB5热变形的本构方程，以此来描述硼钢高温下的热流变行为。

Hot tensile tests of 22MnB5 were carried out with Gleeble-1500 at the temperatures va- rying from 500 ℃ to 950 ℃ and at the strain rates of 0.01s-1 , 0. ls-1, 1s-1 to study its hot deforma- tion behavior at high temperature. Afterwards, microstructure analysis of the cross sections of speci- mens was conducted to clarify the relationship between microstructure and hot deformation of boron steel under different conditions. The results show that the mechanism of hot deformation of 22MnB5 belongs to dynamic recovery and that the flow stress decreases with the increase of temperature and with the reduction of strain rate. In addition, the influence of temperature is more obvious than it of strain rate. However, the flow stress at the temperature of 500 ℃ and at the strain rate of 0.01s-1 is higher and the result seems a little different to the above law. Finally, constitutive model was estab- lished to represent the behavior of hot deformation of boron steel at high temperature.