40CrMnSiB钢的热变形行为与本构方程建立

THE THERMAL DEFORMATION BEHAVIOR OF 40CrMnSiB STEEL AND ESTABLISHING WITH THE CONSTITUTIVE EQUATION

40CrMnSiB是一种新型中碳含硼结构钢,利用Gleeble-3800热模拟试验机对40CrMnSiB进行高温压缩试验,得到变形温度为800~1 100℃、应变速率为0.01~50 s^(-1)、压缩变形量60%的轴向单道次压缩条件下的真应力-真应变曲线,利用Arrhenius双曲正弦函数,确定其热变形激活能,建立该钢的流变应力本构方程。结果表明:40CrMnSiB钢在800~1 100℃进行压缩试验时,存在动态回复和动态再结晶两种软化机制,其流变应力随应变速率的升高和变形温度的降低而升高;在高温低应变变形时,软化机制主要为动态再结晶;在高温高应变变形时,软化机制主要为动态回复;在低温低应变时,加工硬化占主导作用。其热变形激活能Q为299.02 kJ/mol,应力指数为4.478 9,峰值应力的预测值与测量值之间的平均相对误差为3.86%,预测精度较高,可为40CrMnSiB钢热加工工艺制定提供相应理论依据。

40CrMnSiB is a new type of medium carbon boron-containing structural steel,the Gleeble-3800 thermal simulation testing machine was used to carry out high temperature compression test on 40CrMnSiB,and the deformation temperature was 800~1100℃,the strain rate was 0.01~50 s^(-1),and the compression deformation was 60%.The true stress-true strain curve under the condition of axial single-pass compression,the activation energy of thermal deformation is determined by using the Arrhenius hyperbolic sinusoidal function,and the rheological stress constitutive equation of the steel is established.The results show that there are two softening mechanisms of 40CrMnSiB steel under compression test at 800~1100℃,dynamic recovery and dynamic recrystallization,and the rheological stress increases with the increase of strain rate and deformation temperature,the softening mechanism is mainly dynamic recrystallization at high temperature and low strain deformation,dynamic recovery is mainly at high temperature and high strain deformation,and work hardening plays a dominant role at low temperature and low strain.The activation energy Q of thermal deformation is 299.02 kJ/mol,the stress index is 4.4789,and the average relative error between the predicted value of peak stress and the measured value is 3.86%,which has a high prediction accuracy,which can provide a corresponding theoretical basis for the formulation of hot working technology of 40CrMnSiB steel.