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以BVRE重轨钢为研究对象,通过真空冶炼、锻造和轧制工艺制备合格的重轨钢试样。在此基础上,系统研究稀土重轨钢奥氏体晶粒的长大动力学。实验结果表明,随着加热温度的提高,稀土重轨钢奥氏体晶粒呈指数关系长大;随着保温时间的延长,稀土重轨钢奥氏体晶粒长大呈抛物线规律。重轨钢中添加微量的稀土,可以明显降低不同加热条件下的奥氏体晶粒尺寸。模型计算结果表明,重轨钢的奥氏体晶粒长大公式分别为:d4.80=d40.80+2.82×1028texp(-556450/RT)(不加稀土)和d5.34=d50.34+4.52×1032texp(-646890/RT)(稀土重轨钢)。稀土主要通过晶界的偏聚机制使奥氏体晶粒长大激活能由556450J.mol-1增加到646890J.mol-1,从而抑制奥氏体晶粒尺寸的增加。
Taking BVRE heavy rail steel as the research object, qualified heavy rail steel samples were prepared by vacuum smelting, forging and rolling process. On this basis, the kinetics of austenite grain growth in rare earth heavy rail steel was studied systematically. The experimental results show that with the increase of heating temperature, the austenite grains of rare earth heavy rail steel grow exponentially. With the increase of holding time, the austenite grain growth of rare earth heavy rail steel presents a parabolic law. Adding a trace amount of RE in heavy rail steel can obviously reduce austenite grain size under different heating conditions. The calculation results of the model show that the grain growth of austenite in heavy rail steel is: d4.80 = d40.80 + 2.82 × 1028texp (-556450 / RT) (without rare earth) and d5.34 = d50.34 + 4.52 × 1032texp (-646890 / RT) (rare earth heavy rail steel). The RE activates the growth of austenite grains from 556450 J · mol-1 to 646 890 J · mol-1, mainly through the segregation mechanism of the grain boundaries, thus inhibiting the increase of austenite grain size.