齿轮钢SAE8620 H高温变形行为及热加工图

通过高温压缩试验研究齿轮钢SAE8620H在950~1100℃、应变速率0．01~10 s-1条件下的高温变形行为.该合金钢的流动应力符合稳态流变特征，流变应力随变形温度升高以及应变速率降低而减小，其本构方程可以采用双曲正弦方程来描述.基于峰值应力、应变速率和温度相关数据推导出SAE8620H高温变形激活能Q=280359．9 J·mol-1.根据变形量40%和60%下应力构建该齿轮钢的热加工图，通过热加工图中耗散值及流变失稳区确定其热变形工艺参数范围. SAE8620H钢在在变形程度较小时宜选取低的应变速率进行成形，而在变形程度大时则要选取低温低应变速率或者高温高应变速率.

High temperature deformation behavior and processing maps of SAE8620 H gear steel

The high temperature deformation behavior of SAE8620H gear steel in a temperature range of 950 to 1100℃ and a strain rate range of 0. 01 to 10 s-1 was studied by high temperature compression tests. The flow stress of the steel has steady state char-acteristics. The flow stress decreases with the increase of deformation temperature and the decrease of strain rate. The constitutive e-quation of the steel can be described by a hyperbolic sine equation. Based on the related data of peak stress, strain rate and tempera-ture, the hot deformation activation energy of the steel was deduced to be about 280359. 9 J·mol-1 . The processing maps were drawn according to 40% and 60% deformation. The forming parameters can be determined by the processing maps. Low strain rate should be used for small deformation, while high strain rate and high forming temperature or low strain rate and low forming temperature should be used for large deformation.