车轴钢高温黏塑性本构模型及流变行为分析

高温黏塑性本构模型是连铸坯近凝固终点压下工艺数值模拟的基础，但该条件下的应力应变数据极为缺乏，严重限制了连铸新工艺的开发.利用热模拟实验对比研究了车轴钢在近凝固终点压下和常规热变形工艺下的流变行为.结合动态回复和动态再结晶理论构建了近凝固终点压下工艺下的本构模型.结果表明:在近凝固终点压下工艺下，类铸态组织奥氏体晶粒粗大，流变应力明显低于常规热变形工艺下的流变应力;同一变形量下，动态再结晶体积分数较大.本文构建的本构模型对不同变形条件下的应力预测值与实验值吻合较好，平均相对误差约为2.62%.

High-Temperature Viscoplastic Constitutive Model and Rheological Behavior Analysis for Axle Steel

A high-temperature viscoplastic constitutive model is the basis of numerical simulation on the deformation behaviors of continuous casting billet in a near-solidification-finishing reduction(NSFR) process. However， the lack of the stress and strain data under this condition extremely limits the development of new continuous casting processes. The rheological behaviors of axle steel under the NSFR and conventional hot deformation processes are studied through thermal simulation experiments. Based on the theory of dynamic recovery and recrystallization， a revised constitutive model in the NSFR process is established. The results show that the austenite grains are coarser and the rheological stress is lower under the NSFR process， compared with those under the conventional one. Under the same reduction， the volume fraction of dynamic recrystallization grain is higher. The predicted stresses from the constitutive model under different conditions are in good agreement with the experimental ones and the average relative error is about 2.62%.