20CrMnTiH齿轮钢高温塑性变形特性

以20CrMnTiH齿轮钢为研究对象，在变形温度850~1 150 °C和应变速率0.01~10 s-1的变形条件下，采用高温压缩热模拟实验研究其塑性变形特性.发现：变形温度850 °C时的流动应力为1 150 °C时的2~3倍，应变速率10 s-1时的应力值为应变速率0.01 s-1时的2~3倍，在高温和低应变速率的条件下发生了连续动态再结晶；从微观组织来看，随变形温度升高，再结晶晶粒沿着初始晶粒的晶界长大并形成新晶粒，变形温度1 050 °C时，多次动态再结晶使得晶粒长大明显.根据采用双曲正弦函数修正的Arrhenius方程，利用线性回归法求出相应的热变形激活能为371.053 kJ/mol.利用加工图确定了相应的热变形过程最佳工艺参数范围，即变形温度为1 020~1 150 °C，应变速率为0.5~2.5 s-1.

Plastic Deformation Characteristics of 20CrMnTiH Gear Steel under High Temperature

Taking the 20CrMnTiH gear steel as an object, under the condition of deformation temperature of 850 °C-1 150 °C and strain rate 0.01 s-1-10 s-1, different high temperature compression tests were carried out to investigate its plastic deformation characteristics. The flow stress under 850 °C is 2 to 3 times the stress under 1 150 °C, and the stress at strain rate 10 s-1 is 2 to 3 times the stress at strain rate 0.01 s-1. Under high temperature and low strain rate, the phenomenon of continuous dynamic recrystallization (CDRX) takes place. From the microstructure, the recrystallized grains along initial grain boundaries grow and new grains generate with the increase of deformation temperature, and the grains grow up significantly because of CDRX when the temperature is 1 050 °C. The hot deformation activation energy of the steel is 371.053 kJ/mol. Based on the processing map, the optimum processing parameters of hot deformation are obtained, that is,the deformation temperature is 1 020 °C-1 150 °C and the strain rate is 0.5 s-1-2.5 s-1.
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