17Cr2Ni2MoVNb和20Cr2Ni4A齿轮钢的热变形行为

Thermal deformation behavior of 17Cr2Ni2MoVNb and 20Cr2Ni4A gear steels

利用Gleeble-3800热模拟试验机,研究了17Cr2Ni2MoVNb和20Cr2Ni4A齿轮钢的热变形行为。利用加工硬化曲线,计算了两种齿轮钢的热变形激活能,构建了本构方程。结果表明:两种齿轮钢在低应变速率下,均表现出明显的动态再结晶;而在高应变速率下,20Cr2Ni4A钢在1000℃时表现为动态回复,而17Cr2Ni2MoVNb钢在1000~1150℃时均表现为动态回复。在相同变形条件下,17Cr2Ni2MoVNb钢的峰值应力和临界应力均高于20Cr2Ni4A钢;20Cr2Ni4A钢和17Cr2Ni2MoVNb钢的热变形激活能分别为324和374 kJ·mol^(-1)。两种齿轮钢之间的应力特征值和热变形激活能之间的差异主要是由于Ni、Mo和Nb元素的含量差异对动态再结晶有不同程度的影响而导致的。在低应变速率下,两种齿轮钢可选的变形温度相同;在高应变速率下,17Cr2Ni2MoVNb钢的加工温度选择可高于20Cr2Ni4A钢的加工温度100℃以上的温度。

The thermal deformation behavior of 17Cr2Ni2MoVNb and 20Cr2Ni4A gear steels were studied by Gleeble-3800 thermal simulation test machine,respectively,and the thermal deformation activation energy for the two kinds of gear steels was calculated to construct the constitutive equation by the work hardening curves.The results show that the two kinds of gear steels exhibit obvious dynamic recrystallization at low strain rate,while at high strain rate,20Cr2Ni4A steel exhibits dynamic recovery at 1000℃and 17Cr2Ni2MoVNb steel exhibits dynamic recovery at 1000-1150℃.Under the same deformation conditions,the peak stress and critical stress of 17Cr2Ni2MoVNb steel are higher than those of 20Cr2Ni4A steel,and the thermal deformation activation energy of 17Cr2Ni2MoVNb and 20Cr2Ni4A steels are 374 and 324 kJ·mol^(-1),respectively.The difference between the stress characteristic values and the thermal deformation activation energy between the two kinds of gear steels is mainly due to the different contents of Ni,Mo and Nb,which have different effects on dynamic recrystallization.At low strain rate,the optional deformation temperature for the two kinds of gear steels is the same,while at high strain rate,the processing temperature of 17Cr2Ni2MoVNb steel can be selected to be more than 100℃higher than that of 20Cr2Ni4A steel.