316LN高温热变形行为与热加工图研究

Hot Deformation Behavior and Hot Processing Maps of 316LN Stainless Steel

通过Gleeble热模拟实验机在1000~1200℃,应变速率为0.01~10 s^(-1)条件下的近等温热模拟压缩实验,建立了316LN双曲正弦的流动应力预测模型及其热加工图。该流动应力预测模型考虑了实验过程中塑性变形和摩擦引起的温升,对流动应力进行了修正,考虑应变对流动应力预测模型参数的影响,获得了统一流动应力预测模型,模型预测值与实验值的相关系数为0.992,平均相对误差为4.43%;热加工图基于Prasad动态材料模型分别获得了不同应变速率、温度条件下的能量耗散率和失稳系数;分析了应变量、温度和应变速率对于能量耗散率和失稳系数的影响。结果表明:实验条件下最大能量耗散率值为0.38,且高应变速率下失稳,并通过显微组织分析对热加工图进行了验证。

Isothermal compression tests of 316 LN stainless steel at temperatures ranging from 1000 to 1200 oC and strain rates from 0.01 to 10 s^-1 were performed on Gleeble thermo-simulation machine.Based on hyperbolic sine function,the constitutive equations of 316 LN stainless steel and hot processing maps during the hot deformation process were established.The flow stresses were corrected via considering the temperature rise induced by plastic deformation and friction during the test process.In addition,by taking the influence of strain on flow stress into account,a unified constitutive model for predicting flow stress was proposed.The flow stress predicted by the constitutive equations shows good agreement with the corrected stress when R is 0.992 and ARRE is 4.43%.According to the dynamic material model presented by Prasad,hot processing maps for hot working condition were established based on the effect of power dissipation and instability coefficient associated with various kinds of temperatures and stain rates.Subsequently,efficiency of power dissipation and instability coefficient were interpreted based on hot processing maps under a series of strains,temperatures and strain rates.The results show that efficiency of power dissipation increases gradually with the increasing temperature and the decreasing stain rate,and it is noted that the maximum of efficiency of power dissipation is 0.38.An optimum zone for 316 LN stainless steel is obtained and verified effectively by the analysis of microstructure.