Modeling Flow Stress of 70Cr3Mo Steel Used for Back-Up Roll During Hot Deformation Considering Strain Compensation

A constitutive model incorporating the influence of strain developed based on the Arrhenius equation by considering the variation of material constants as a fifth polynomial function of strain is presented. Materials con- stants are fit to data from hot compression tests of 70Cr3Mo steel used for back-up roll at the temperatures from 1 173 to 1 473 K and strain rates from 0.01 to 10 s ~ by using a Gleeble-1500D thermo-mechanieal simulator. The de- veloped constitutive model is then used to predict the flow stress under all the tested conditions. The statistical pa- rameters of correlation coefficient and average absolute relative error are used to analyze the predictable efficiency and the values are 0. 997 and 3. 64%, respectively. The results show a good agreement between experimental stress and predicted stress.

微观组织对70Cr3Mo钢接触疲劳性能的影响

采用金相、ＳＥＭ、ＴＥＭ、ＸＲＤ等手段，研究了钢不同热处理条件下７０Ｃｒ３Ｍｏ的组织对接触疲劳性能的影响，结果表明：７０Ｃｒ３Ｍｏ钢直接淬火＋回火条件下以孪晶马氏体为主的组织的接触疲劳性能高于等温淬火＋回火条件下贝氏体的接触疲劳强度。

接触疲劳形貌与组织的关系

在研究测试轧辊材料70Cr3Mo钢接触疲劳性能的基础上，应用SEM、TEM对接触疲劳坑的形貌、组织进行观察和分析。结果表明：不同的热处理方式所得的组织形态不同，其剥落坑形貌、裂纹的起裂和扩展机理也不尽相同；疲劳坑形貌特征与疲劳寿命相关。

70Cr3Mo钢动态再结晶临界条件研究

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。