铌含量对低碳微合金钢回复再结晶行为的影响

Efect of niobium on the recovery and recrystallization behavior of low-carbon micro-alloyed steel

采用应力松弛实验研究了低C含Nb微合金钢奥氏体热变形过程中的析出及再结晶动力学过程,通过实验及理论模型分析了析出/溶质拖曳对回复和再结晶行为的影响.结果显示:随Nb含量的增加,析出动力学曲线的鼻尖温度上升,但鼻尖温度对应的时间变化不大,约为20～30s;析出可明显抑制再结晶的发生,增加Nb含量将使非再结晶温度升高;Nb溶质通过拖曳作用阻碍晶界运动,减小了晶界迁移率,最终减慢再结晶过程的发生;对于低C含Nb实验钢,拟合得到再结晶激活能与Nb质量分数的0.5次方成正比.

The kinetic processes of recrystallization and precipitation in low carbon steels with different Nb contents were studied by stress-relaxation method. The effects of Nb solute drag and its precipitation on the recovery and recrystallization behavior were analyzed by the experiment and theoretical model. When the Nb content increases, the nose temperature of precipitation kinetic curves （PTT） rises, but the time of precipitation corresponding to the nose temperature changes a little, which is about 20 to 30 s. The precipitation can obviously restrain the recrystallization process, and increasing the Nb content makes the non-recrystallized temperature rise. The Nb solute drag can inhibit the mobility of grain boundaries, lead to the decreasing mobility rate of grain boundaries, and finally cause the process of recrystallization retarded. The recrystallized activation energy is linear with the square root of Nb mass fraction.