316LN钢的高温本构模型与热加工图

High Temperature Constitutive Model and Hot Processing Map of 316LN Stainless Steel

目的研究316LN钢的高温变形行为,确定最佳加工区间并优化工艺参数。方法利用Gleeble热模拟实验机在变形温度为1000~1150℃、应变速率为0.001~10 s^(-1)条件下对316LN钢进行热压缩实验。根据实验数据分别绘制不同变形温度和不同应变速率下的流变应力曲线。在传统Arrhenius双曲正弦关系的基础上,考虑应变量的影响,通过五次多项式拟合建立316LN钢的改进型本构模型,基于动态材料模型及Prasad塑性失稳判据计算得到材料的能量耗散图和流变失稳图,将二者叠加得到316LN钢的热加工图。结果流变应力曲线呈现典型的动态再结晶特征,且随着应变速率的增大和变形温度的升高,316LN钢的压缩应力逐渐减小,耦合应变量的本构模型预测值与实验值的相关系数达0.9888,吻合度较高。通过建立热加工图并对比金相组织发现,316LN钢在“安全区”能量耗散效率较大的区域更容易发生动态再结晶行为。结论高变形温度、低应变速率条件更有利于软化机制的发生,改进型本构模型精度较高,可对316LN钢热变形过程中的流变应力进行准确预测。通过构建热加工图确定了316LN钢的最佳工艺区间:温度为1035~1065℃、应变速率为0.001~0.03 s^(-1)以及温度为1100~1150℃、应变速率为0.035~0.1 s^(-1)。

The work aims to study the deformation behavior of 316LN steel at high temperature,determine the best working interval and optimize the process parameters.The hot compression experiment of 316LN steel was carried out on the Gleeble thermal simulation machine at the deformation temperature of 1000-1150℃and the strain rate of 0.001-10 s^(-1).According to the experimental data,the flow stress curves at different deformation temperature and strain rate were drawn respectively.Based on the traditional Arrhenius hyperbolic sinusoidal relationship,the improved constitutive model of 316LN steel was established by means of quintic polynomial fitting considering the effect of strain variables.Based on the dynamic material model and Prasad plastic instability criterion,the energy dissipation map and flow instability map of the material were calculated,and the hot processing map of 316LN steel was obtained by superposition of the two graphs.The results showed that the flow stress curve presented a typical dynamic recrystallization characteristic,and with the increase of strain rate and deformation temperature,the compressive stress of 316LN steel gradually decreased.The correlation coefficient between the predicted value and the experimental value of the coupled strain variable was 0.9888,which showed a high coincidence.Through the establishment of the hot processing map and the comparison of metallographic structure,it was found that the dynamic recrystallization of 316LN steel was more likely to occur in the zone with higher energy dissipation rate in the"safe zone".This indicates that the softening mechanism is more favorable under the conditions of high deformation temperature and low strain rate.The improved constitutive model has high accuracy and can accurately predict the flow stress of 316LN steel during the hot deformation process.The optimal process range of 316LN steel is determined by the constructed hot processing map:The temperature is 1035-1065℃,the strain rate is 0.001-0.03 s^(-1),the temperature is 1100-1150℃and the strain rate is 0.035-0.1 s^(-1).