高速车轮钢的组织韧化工艺及机理研究

为改善高速车轮钢韧性,从而提高高速车轮运行安全性,通过改变辗轧变形温度(tD)及踏面淬火温度(tQ),系统研究了热处理工艺对车轮钢力学性能的影响.采用光学、扫描电子显微(SEM)技术、电子背散射技术(EBSD)、定量金相技术等研究了车轮钢珠光体组织.试验结果表明:车轮钢韧性随着tD与tQ的降低而升高,强度变化不大;tD与tQ的降低导致奥氏体晶粒尺寸减小,同时得到细化的珠光体球团组织,是韧性优化的直接原因.进一步断口分析与EBSD分析表明,单个珠光体球团可形成一个解理面,且解理面滑移带终止于珠光体球团界,与珠光体球团内部小角度晶界相对应,可认为珠光体球团是车轮钢韧性的控制单元.

Study on the processing and mechanism of improved toughness of high-speed railway wheel steels

The effect of heat treatment processing,including change in deformation temperature(tD) and quenching temperature(tQ),on mechanical properties of a railway wheel steel,especially toughness,had been systemically investigated.Optical microscopy,scanning electron microscopy(SEM),electron backscatter diffraction(EBSD) and quantitative metallographic technology had been employed to research the microstructure of the steel.The results show that the toughness improves with the decreasing of tD and tQ,while strength stays at the same level.The reason of improvement in toughness is that the prior austenite grain size is refined by decreasing tD and tQ and thus refined pearlite colony is obtained.Further study in fracture surface reveals that single pearlite colony could form into a fracture facet and slip bands in a facet ended at pearlite colony boundaries.These slip bands could be related with low angle grain boundaries within one pearlite colony through EBSD analysis.So it is reasonable to consider that the pearlite colony was the controlling factor for the microstructure of railway wheel steels.