【作者】 罗平；

【导师】 白秉哲；

【作者基本信息】 北京交通大学 ， 材料科学与工程， 2016， 硕士

【摘要】 本论文研究了Mn-Si-Cr系贝氏体钢轨用钢的组织演变规律及不同形态贝氏体对其强韧性和抗磨损性能的影响规律,并获得了优化的钢轨用钢热处理方案。以此为基础,进一步研究了实际贝氏体钢轨钢和珠光体钢轨钢的抗磨损和抗接触疲劳性能。等温贝氏体和连续冷却组织演变规律结果表明：贝氏体钢轨钢具有良好的贝氏体淬透性,在较宽冷却速度(0.05℃/s～8℃/s)范围内可得到贝氏体/马氏体复相组织,当冷却速度处于0.25℃/s～8℃/s范围内时奥氏体向贝氏体和马氏体转变动力学相差不大；为该贝氏体钢轨钢采用空冷冷却方式的可能性提供了科学依据。回火对空冷贝氏体钢轨的研究结果表明：该贝氏体钢轨钢具有较高的回火抗力,当回火温度为280℃时贝氏体钢轨钢的强韧性匹配较佳且经280℃回火后残余奥氏体的热稳定性和机械稳定性较高；为贝氏体钢轨钢的回火工艺提供了科学依据。工业化生产贝氏体钢轨在空冷条件下组织转变过程较复杂；并工业化生产的贝氏体钢轨具有良好的强韧性匹配、其抗磨损和抗接触疲劳性能均较佳。根据贝氏体钢轨钢的贝氏体等温转变、连续冷却转变规律及贝氏体钢轨空冷过程中组织转变规律设计了三种不同热处理工艺以得到含有不同形态贝氏体的贝氏体/马氏体复相组织。结果表明：针状贝氏体/马氏体复相组织比粒状贝氏体/马氏体复相组织的强韧性高、抗磨损性能好。本论文较系统地研究了贝氏体钢轨钢的贝氏体等温淬火和连续冷却转变组织规律和工业化空冷贝氏体钢轨组织演变规律。基于上述演变规律设计相应热处理工艺,得到不同形态的贝氏体/马氏体复相组织,从而调控贝氏体钢轨钢的性能。更多还原

【Abstract】 The evolution of microstructure and the effect of bainitic morpholinogy on the properties of impact wear resistance of bainitic railway steel were investigated in the present work.The resistance to wear and rolling contact fatigue (RCF) of a Mn-Si-Cr seriou bainitic railway steel and conventional pearlite railway steel were studied using a RCF testing mechine and impact wear testing machine.The microstructure evolution during austempering and continous cooling as well as the relation between microstructure and properties were analyzed. And it indicated that the bainitic railway steel showed excellent bainitic hardability. Bainite/martersite multiphase microstructure can be obtained with a wide cooling rate (0.05℃/s～8℃/s). When the cooling rate is between 0.25℃/s～8℃/s, the kinetic processes of continuous cooling phase transformation are almost the same. So, it was confirmed that the scientific basis for the ability that this kind of bainitic railway can be air cooled. The effects of tempering processes on properties were analyzed. The result suggested that the tempering resistance of this kind of bainitic railway steel is very high. And the combination of strength and toughness is excellent after tempering at 280℃. Comparing with the air cooling bainitic railway steels (without tempering), the thermal and mechanical stability of retained austenite were enchanced after tempering at 280℃. Thus, the influence of tempering after air cooling was investigated which is of great importance for practical manufacture of this seriou bainitic railway. The microstructure evolution and mechanical properties were discussed of practical manufacturing bainitic railway. It indicated that the process during bainitic air cooling is relatively complex. And the properties of actual manufacturing bainitic rail are very favorable.According to CCT, TTT, and the microstructure of air cooling bainitic railway, three heat treatment processes were designed. The result suggested that the properties (such as the combination of strenghth and toughness, the resistance to wear) of acicular bainite/martensite railway steel are superior to granular bainite/martensite railway steel.In conclusion, the evlution of microstructure during austempering and continous cooling of this kind of bainitic railway steel and actual processes during manufacture were explored systematacially in this study. And based on the above results three heat treatments were designed to tailor microstructure, thus to controlling the properties of bainitic railway steels.更多还原