多元微合金低碳钢的奥氏体晶粒生长及淬火硬度

Austenite Grain Growth and Quenched Hardness of Multi-microalloyed Low Carbon Steel

针对一种多元微合金化低碳钢的奥氏体晶粒长大行为展开研究,采用光学显微镜观察淬火组织及原始奥氏体晶界特征,并分析其在不同工艺下的显微硬度。结果表明:当加热温度较低时,原始奥氏体晶粒细小且粒径分布较为均匀,第二相粒子的钉扎作用抑制了晶界的快速迁移,表现出正常长大趋势。当加热温度为1 200℃时,大部分第二相粒子溶解,原始奥氏体晶粒出现异常长大。淬火马氏体形态学特征表明了原始晶粒尺寸对最终力学性能的影响,高的淬火温度有利于提高淬透性和获得较高且稳定的显微硬度。

The austenite grain growth behavior of a multi - microalloyed low carbon steel is described, the quenched microstructure and prior austenite grain boundaries are observed by means of optical microscope, the micro-hardness at different processes is analyzed. The results show that when the reheating temperature is lower, the grain size is small and its distribution is even, the pinning effect of second phase particles inhibits the rapid migration of grain boundary, which leads to normal growth. As the reheating temperature is 1 200 °C , most of the second phase particles are dissolved and abnormal growth of prior austenite grains occurs. The morphology of martensite shows that prior austenite grain size determines final mechanical properties. Higher reheating temperature is in favor of improving hardenability and attaining higher and stable microhardness.