稀土轨钢过冷奥氏体转变机理及CCT曲线的预测方法

Supercooled Austenite Transformation Mechanism of Rare Earth Microalloy Rail Steel and Method of Predicting CCT Diagram

通过金相观察、扫描电镜分析、能谱分析、电化学萃取定量相分析等方法，研究了稀土和铌元素对稀土微合金重轨钢热处理性能的影响机理．结果表明，铌影响碳的扩散是铌提高轨钢淬透性的主要机理；稀土通过在晶界偏聚和影响碳的扩散而对过冷奥氏体产生一定的影响；而稀土轨钢淬透性提高的主要原因在于硅锰含量的增加．在机理分析的基础上，建立了该钢种过冷奥氏体等温转变和连续冷却转变曲线的预测方法．

Heavy rail steel microalloyed with rare earth is a new generation of rail steel recently developed in our country. The mechanism of how the rare earth(RE) and niobium(Nb) affect the heat treatment of this steel is studied in this paper by use of microscopic examination, SEM, energy analysis, electrochemistry extractive quantitative metallographic analysis, etc. The results show that the mechanism of Nb improving the hardenability of the rail steel is mainly because of the Nb changes the carbon diffusion, and the RE has some effects on the supercooled austenite by means of its partial accumulation at grain boundaries and its effects on the carbon diffusion, while the improvement of the hardenability of the steel is mainly caused by the increase of silicon and manganese. Based on the studies mentioned above, a method of predicting TTT and CCT of supercooled austenite for the steel has been developed.