利用热力模拟实验技术、OM及TEM等, 研究了一种低碳含V微合金钢在温度为900-1150℃及应变速率为0.01-10 s-1条件下奥氏体动态再结晶和析出行为. 采用回归法确定了该微合金钢的热变形激活能和表观应力指数,建立了该钒微合金钢的热加工方程; 根据应变硬化率与应力的P-J方法, 结合高阶多项式拟合, 精确确定了动态再结晶临界应变值, 获得了临界应变、峰值应变与Z参数之间的关系; 最后, 研究了低应变速率变形时该钢中V(C, N)粒子的动态析出行为. 结果表明, 在某一变形温度和应变速率下, 随着应变的进行,V(C, N)粒子的平均尺寸增加, 且尺寸分布范围变宽; 再结晶驱动力和钉扎力的计算结果表明, 一旦动态再结晶开始发生, 动态析出就不能阻止动态再结晶过程的进行.
By using thermo–mechanical simulator, OM and TEM, the dynamic recrystallization (DRX) and precipitation behaviors of a kind of low carbon V–microalloyed steel have been investigated at temperatures ranging from 900 to 1050℃ and strain rates from 0.01 to 10 s−1. The activation energy (Qdef ) for hot deformation of this kind of V–microalloyed steel was calculated to be 341.97 kJ/mol by regression analysis, while the apparent stress exponent (n) was calculated to be 4.24. The equation describing the hot working process was also obtained. The critical strain for DRX was accurately determined based on the P–J method and high order polynomial fitting between strain hardening rate and true stress, and mathematical models of critical strain and peak strain versus Z parameter were deduced. The dynamic precipitation behavior of V(C, N) particles at low strain rate was further investigated. The results show that with increasing the strain, the average size of V(C, N) particles increases and the size distribution of the precipitates become wide. The calculations of the driving force for recrystallization and pinning force show that once the dynamic recrystallization take place, the dynamic precipitation could not prevent dynamic recrystallization from occurring.
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