低碳齿轮钢18CrNiMo7-6奥氏体晶粒度长大规律

The Austenite Grain Growth Behavior of Low Carbon Gear Steel 18CrNiMo7-6

利用金相实验法研究了低碳齿轮钢18CrNiMo7-6在不同加热条件下奥氏体晶粒的长大行为,建立了Arrhenius奥氏体晶粒长大模型,并利用时间指数对模型进行了优化。结果表明:在1173~1373 K范围内,奥氏体晶粒平均尺寸随着温度的升高及时间的延长而增大,并且对温度的敏感性高于对时间的敏感性,显著粗化温度为1273 K;建立了Arrhenius奥氏体晶粒长大模型D=2.223×10^(6)exp[-132086/(RT)]tn,其中激活能Q=132.086 kJ/mol;时间指数n随温度的变化近似服从S型函数,并建立了相关的数学方程式n=0.0775+0.2317/(1+10(1326.73-T)×0.0235),用该方程式对考虑合金元素的Arrhenius方程中的时间指数进行了优化,将优化后由该模型得到的奥氏体晶粒平均尺寸的计算值与实测值进行了对比,结果显示其吻合性较未优化前的模型更好。

The austenite grain growth behavior of low carbon gear steel 18 CrNiMo7-6 under different heating conditions was studied by metallographic technique,and an Arrhenius growth model for the average austenite grain size was established,then was optimized by using time exponent.The results showed that the average austenite grain size gradually increased with the temperature and time increasing from 1173 K to 1373 K,and the sensitivity to temperature was higher than that to time,and the apparent coarsening temperature was 1273 K.The classical Arrhenius growth model for austenite grain size was established:D=2.223×10^(6)exp[-132086/(RT)]tn,with the activation energy Q=132.086 kJ/mol.The time exponent n approximately coincided the S-type function with the change of temperature,and the relevant mathematical equation was established:n=0.0775+0.2317/(1+10(1326.73-T)×0.0235),which was used to optimize the time exponent in the Arrhenius equation considering alloy-element.The calculated value of average austenite grain size was compared with the measured value after optimization,and the results show that the consistency of the model was better than that of the unoptimized model.