奥氏体化温度对调质Ti--V微合金钢力学性能的影响

摘要

Experiments were performed to investigate the effect of austenitizing temperature on the mechanical properties of quenched and tempered Ti-V microalloyed steel. Metallographic and transmission electron microscopy ( TEM) observations reveal the variation of austenite grain size with austenitizing temperature. Within the temperature range of 850 to 1200℃, the austenite grain size experiences three phases, which are stable, rapidly increased, and stable again. Tensile strength and impact toughness tests show that, when the austenitizing temperature rises, the tensile strength Rm increases gradually, but the impact toughness undergoes a process of stabilizing, decreasing and then increasing. At a certain temperature, coarsening of precipitated particles leads to the sudden increase of austenite grain size. The increase of diffuse precipitates resulting from continuous solutionizing of microalloying elements with temper-ature rise and the effective pinning of precipitated particles are the main reasons for the increase of tensile strength, while abnormal grain growth and grain size uniformity at a certain temperature are the key factors that influence the toughness of the steel.%研究了奥氏体化温度对调质Ti-V微合金钢力学性能的影响。金相和透射电镜观察揭示了奥氏体晶粒尺寸随奥氏体化温度的变化规律。在850~1200℃的温度范围内，随着奥氏体化温度的升高，奥氏体晶粒尺寸经历了稳定-骤增-稳定三个阶段。抗拉强度和冲击韧性试验结果显示，实验钢的抗拉强度Rm随着奥氏体化温度的升高逐渐增加，而冲击韧性则经历了稳定-降低-升高的过程。一定温度下沉淀相粒子的粗化导致了奥氏体晶粒尺寸的突然增加；随温度升高，合金元素不断固溶所导致的回火后弥散析出的增多和沉淀相粒子的有效钉扎是抗拉强度增加的主要原因，而一定温度下晶粒的不正常长大和尺寸均匀化则是影响实验钢冲击韧性的关键因素。