40CrNiMo钢的热变形特征及变形抗力模型

Hot Deformation Characteristics and Deformation Resistance Model of 40CrNiMo Steel

采用Gleeble-3500型热模拟试验机对40CrNiMo钢进行了单道次热压缩试验,得到了其在应变速率0.1~50s^(-1)、变形温度800~1 100℃下的应力-应变曲线,观察了变形后的显微组织并分析了热变形特征;建立了该钢的变形抗力模型并进行了试验验证。结果表明:较高的变形温度或较低的应变速率更有利于40CrNiMo钢的完全动态再结晶;变形温度为800℃时,应变速率增大使动态再结晶晶粒增多;应变速率为10s^(-1)条件下,当变形温度由800℃升至900℃时,动态再结晶晶粒增多,变形温度为1 000℃时,40CrNiMo钢发生了完全动态再结晶,变形温度为1 100℃时,动态再结晶晶粒长大;计算得到40CrNiMo钢的动态再结晶激活能为322.53kJ·mol^(-1);由周纪华-管克智模型计算得到的变形抗力与试验值的平均相对误差为4.82%,模拟精度较高。

The stress-strain curves of 40 CrNiMo steel at the strain rates of 0.1-50 s^-1 and deformation temperatures of 800^-1 100 ℃ were obtained by single pass hot compression experiment on the Gleeble-3500 thermo-simulation machine.The microstructure after deformation was observed and the hot deformation characteristics of 40 CrNiMo steel were analyzed.The deformation resistance model of the steel was established and verified by experiments.The results show that the relatively high deformation temperature or relatively small strain rate were favorable for the complete dynamic recrystallization of 40 CrNiMo steel.When the deformation temperature was 800 ℃,the amount of dynamic recrystallization grains increased with the increase of the strain rate.When the strain rate was 10 s^-1,the amount of dynamic recrystallization grains increased when the deformation temperature increased from 800 ℃ to 900 ℃;the complete dynamic recrystallization of 40 CrNiMo steel occured at the defermation temperature of 1 000 ℃;the dynamic recrystallization grains grew up at the deformation temperature of1 100 ℃.The calculated dynamic recrystallization activation energy of 40 CrNiMo steel was 322.53 kJ·mol^-1.The average relative error between deformation resistance calculated by ZHOU Jihua-GUAN Kezhi model and experimental values was 4.82%,indicating a relatively high accuracy.