冷却工艺对Ti微合金化高强钢组织和硬度的影响

Influence of cooling processes on microstructure and hardness of Ti micro-alloyed high strength steel

通过热模拟实验,研究了冷却工艺参数对Ti微合金化高强钢组织和硬度的影响。结果表明:当终冷温度为700℃时,随着冷却速度的增大,铁素体和珠光体组织得到了显著细化,实验钢硬度增加;随着终冷温度的降低,多边形铁素体晶粒尺寸呈减小趋势,铁素体和珠光体含量逐渐降低,珠光体片层间距逐渐减小,贝氏体含量增加,相变强化和细晶强化共同作用使得实验钢的硬度逐渐增加;钢中存在少量粗大的TiN和Ti_(4)C_(2)S_(2)粒子,冷却速度由5℃/s增大到30℃/s, TiC粒子的析出数量明显增加,平均尺寸由8.1 nm减小到6.7 nm;终冷温度由700℃降到600℃,第二相粒子TiC的析出数量逐渐减少,平均析出粒子尺寸由6.7 nm减小到5.9 nm。研究结果为Ti微合金化高强钢控制冷却工艺的制定奠定了理论基础。

Influence of cooling processes on microstructure and hardness of Ti micro-alloyed high strength steel was investigated through thermal simulation experiments. The results indicate that: when the final cooling temperature is 700 ℃, ferrite and pearlite microstructures are refined significantly, and the hardness of the experimental steel increases with the increase of cooling rate;with the decrease of the final cooling temperature, the grain size of polygonal ferrite decreases, ferrite and pearlite contents decrease gradually, pearlite interlaminar spacing decreases gradually, bainite content increases, and the hardness of experimental steel increases gradually resulting from fine grain strengthening and phase transformation strengthening;a small number of TiN and Ti_(4)C_(2)S_(2) particles are found in the experimental steel. When the cooling rate changes from 5 ℃/s to 30 ℃/s, the number of TiC precipitation particles increase gradually, and the average precipitation particle size decreases from 8.1 nm to 6.7 nm;when the final cooling temperature changes from 700 ℃ to 600 ℃, the number of TiC precipitation particles decrease gradually, and the average precipitation particle size decreases from 6.7 nm to 5.9 nm. The research results lay a theoretical foundation for the determination of the controlled cooling process of Ti micro-alloyed high strength steel.