Nb-Ti连铸坯热芯大压下轧制动态再结晶行为研究

采用热模拟单道次压缩实验，研究了Nb-Ti连铸坯热芯大压下轧制中动态再结晶行为及奥氏体晶粒转变规律。结果表明，变形温度越高，应变速率越低，发生动态再结晶的临界应变值越小，动态再结晶越充分。在变形温度1 350 ℃，继续增加应变至0.8和增加应变速率至10 s^-1，奥氏体晶粒尺寸并未得到进一步细化，反而较应变0.5和应变速率5 s^-1下的奥氏体晶粒更加粗大。这是因为高温粘塑性区的金属晶间粘性流动增加，位错增殖速度增大，在动态再结晶过程中会重新形成新的无畸变再结晶晶粒，这些新的无畸变晶粒的亚动态再结晶动力学极快，在较大驱动力下使奥氏体晶界快速迁移，从而使奥氏体发生一定程度的粗化。

Study on dynamic recrystallization in Nb-Ti microalloyed slab during hot-core heavy reduction rolling

Dynamic recrystallization behavior and austenite grain morphology of Nb Ti microalloyed steel during hot core heavy reduction rolling was studied by single pass compression thermal simulation experiment.The result showed that higher deformation temperature and lower strain rate were more advantageous to occur dynamic recrystallization.At higher temperature of 1 350 ℃,when the strain was increased to 0.8 and the strain rate was increased to 10 s^-1,the austenite grain size was no more decreased and even coarsened compared at strain of 0.5 and strain rate of 5 s^-1.This was because the viscous flow between the metal crystals in the high temperature viscoplastic region increased,and the dislocation growth rate increased.During the dynamic recrystallization process,new distortion free recrystallized grains would be reformed.The recrystallization kinetics was extremely fast,and the austenite grain boundaries were rapidly migrated under a large driving force,so that the austenite coarsens to a certain extent.