利用热模拟试验机,在变形温度800~1 050 ℃、应变速率0.01~5 s^-1条件下对20Cr2Ni4A钢进行单道次热压缩试验,对获得的真应力-真应变曲线进行摩擦修正,根据摩擦修正后的曲线,分析了其高温热变形行为,构建了热变形本构模型,绘制了热加工图。结果表明:通过摩擦修正计算得到的流变应力小于实测应力,二者差距随应变增加而增大;当变形温度为850~1 050 ℃,应变速率为0.01~0.1 s^-1时,试验钢在热压缩过程中的动态再结晶较明显;构建的热变形本构模型能够很好地预测试验钢在高温变形时的峰值应力,预测值与实测值的平均相对误差在3.44%;由建立的热加工图结合显微组织,得出试验钢适宜的热变形工艺参数为变形温度875~925 ℃、应变速率0.01~0.02 s^-1和变形温度925~1 050 ℃、应变速率0.01~1 s^-1。

Single-pass hot compression tests were carried out on 20Cr2Ni4A steel at deformation temperatures of 800-1 050 ℃ and strain rates of 0.01-5 s^-1 with thermal simulation test machine. The obtained true stress-true strain curves were modified by friction. According to the curves after frictional modification, the hot deformation behavior of 20Cr2Ni4A steel at high temperature was analyzed, the hot deformation constitutive model was constructed, and the hot processing map was drawn. The results show that the flow stresses calculated by friction modification were smaller than the measured stresses, and the difference between the two increased with the increase of strain. When the deformation temperatures were 850-1 050 ℃ and the strain rates were 0.01-0.1 s^-1, the dynamic recrystallization of the test steel during hot compression deformation was obvious. The hot deformation constitutive model could predict the peak stress of the test steel, and the average relative error between the predicted value and the measured value was 3.44%. According to the established hot processing map combined with the microstructure analysis, the optimum hot deformation parameters of the test steel were listed as follows: deformation temperatures of 875-925 ℃, strain rates of 0.01-0.02 s^-1 or deformation temperatures of 925-1 050 ℃ and strain rates of 0.01-1 s^-1.