冷却路径对V-Ti微合金钢组织性能的影响

 为了获得较大的沉淀强化增量，采用热模拟试验研究了UFC终冷温度和二阶段冷却速度对一种V Ti微合金钢组织和硬度的影响规律。结果表明，协同控制UFC终冷温度和二阶段冷却速度可显著优化V Ti微合金钢的组织性能。UFC终冷温度为750、700和650 ℃时，获得全铁素体组织的临界二阶段冷却速度分别为1.0、1.0和0.2 ℃/s。UFC终冷温度由750降低至650 ℃时，在二阶段冷却速度为0.2~1.0 ℃/s条件下，可将铁素体晶粒由10.5细化至8.4 μm，二阶段冷却速度为5.0 ℃/s时，可将铁素体晶粒由10.5细化至5.1 μm。在750和700 ℃较高UFC终冷温度条件下，适当提高二阶段冷却速度，在650 ℃较低冷却速度条件下，适当降低二阶段冷却速度，均可有效提高试验钢的维氏硬度，试验钢的最大维氏硬度可达到295HV。

Effects of cooling process on microstructure and #br# mechanical properties in a V-Ti bearing steel

In order to obtain a larger increase in precipitation hardening，the effects of UFC final cooling temperature and second stage cooling rate on a V Ti bearing steel were investigated using thermal simulation test. The results show that the microstructure and mechanical properties of the V Ti bearing steel can be optimized significantly by controlling both UFC final cooling temperature and second stage cooling rate. The critical second stage cooling rates to obtain full ferrite microstructure have been estimated to be 1.0，1.0 and 0.2 ℃/s for the UFC final cooling temperatures of 750，700 and 650 ℃，respectively. At the second stage cooling rates of 0.2-1.0 ℃/s， the ferrite grain size can be refined from 10.5 to 8.4 μm by lowering UFC final cooling temperature from 750 to 650 ℃. For a higher second stage cooling rate of 5.0 ℃/s，the ferrite grain size can be refined from 10.5 to 5.1 μm. For the higher UFC final cooling temperatures of 750 and 700 ℃， the Vickers hardness can be enhanced by increasing second stage cooling rate，whereas for a lower UFC final cooling temperatures of 650 ℃，the Vickers hardness can be enhanced by lowering second stage cooling rate. Moreover，the Vickers hardness of the steel can reach 295HV.