中文摘要：

采用Gleeble-1500D热模拟实验机对70Cr3Mo钢进行热模拟压缩实验,变形温度为850-1150℃,应变速率为0.0110 s^-1,用加工硬化率的方法处理实验数据,再结合lnθ-ε曲线的拐点及-（lnθ）/ε-ε曲线最小值判据,建立70Cr3Mo钢热变形过程中的动态再结晶临界应变模型。研究结果表明：实验条件下,70Cr3Mo钢的lnθ-ε曲线均具有拐点特征,对应的-（lnθ）/ε-ε曲线均出现最小值,该最小值所对应的应变即为临界应变;临界应变随变形温度的降低和应变速率的增加而增大;临界应变预测模型可表示为εc=5.4446×10^-2Z^0.01878。

英文摘要：

The hot simulation compression tests of steel 70Cr3 Mo were conducted under conditions of deformation temperature 850-1150 ℃ and strain rate 0. 01-10 s--1by the Gleeble-1500 D thermo-simulation test machine. The critical strain model of dynamic recrystallization for steel 70Cr3 Mo during hot deformation was established by using the work hardening rate method to analyze experimental data,combined with the inflection point criterion of ln θ-ε curves and the minimum value criterion of-（ ln θ） / ε-ε curves. The results show that the ln θ-ε curves of steel 70Cr3 Mo have the characteristics of inflection point and the corresponding-（ ln θ） / ε-εcurve have the minimum value. Therefore,the critical state of this alloy is attained,which means the critical strain. The critical strain increases with the decrease of temperature and the increase of strain rate. The predicting model of critical strain can be described by the function of εc= 5. 4446 × 10^-2Z^0. 01878.