【作者】 杨帅；

【导师】 张福成；

【作者基本信息】 燕山大学 ， 材料学， 2010， 硕士

【摘要】 本文研究的目的是通过探索高锰钢的时效处理来寻找优化高锰钢辙叉制造工艺的途径。高锰钢作为优良的耐磨材料广泛应用于铁路辙叉等耐磨领域,同时作为亚稳材料,室温下即有析出碳化物的趋势,给予能量就可能发生脱溶分解,析出碳化物,使组织与性能发生变化。本论文以辙叉用高锰钢为研究对象,对其进行了普通加热时效、变形时效和应变诱发时效,并运用金相、扫描电镜(SEM)、透射电镜(TEM)和X射线衍射(XRD)等方法研究了不同时效处理后高锰钢微观组织和性能的变化,同时对时效过程中高锰钢的加工硬化和滚动接触疲劳性能进行了分析研究。研究表明:在加热时效中,高锰钢加热到400℃即开始析出碳化物,高锰钢即严重脆化,高锰钢辙叉时效处理最佳温度为350℃;在变形时效中,形变高锰钢首先发生低温回复,硬度下降,随后到脱溶分解的前期和后期,硬度回升和再次下降;在应变诱发时效中,在1800MPa的接触应力作用下,高锰钢在100℃时经过40小时的时效即可完成脱溶分解,析出碳化物。高锰钢时效过程中,随着额外机械能的增加,完成脱溶分解所需要的温度是逐渐降低的。同时研究发现,辙叉用高锰钢在压缩状态下的加工硬化机制主要为孪晶硬化。高锰钢辙叉在服役过程中踏面温升约为150℃。在1800MPa接触应力的作用下,辙叉用高锰钢的滚动接触疲劳寿命约为1.2×106周次,过载量约为5Mt,远远低于实际高锰钢辙叉的过载量。接触表面以疲劳剥落的方式失效。硬化层仅为1.5mm深,最大硬度可达700HV。更多还原

【Abstract】 The purpose of this work is searching methods of optimizing the manufacturing technology of high manganese steel crossing by means of researching the aging treatments of high manganese steel. As an excellent material of wear-resistant materials, high manganese steel has been used extensively in railway crossing and other fields, meanwhile as metastable material, the tendency of precipitated carbide is existed even under room temperature, precipitation decomposition will occur once given energy, separate out carbide and changes of microstructure and properties is aroused.In this paper, the research object is high manganese steel used for crossing. The changes of microstructure and properties of high manganese steel after heating aging, deformation aging and strain induced aging were investigated by means of metallography, SEM , XRD as well as TEM. At the same time , the work hardening mechanism and rolling contact fatigue property of high manganese steel were investigated.The results shows that, during heating aging high manganese steel immediately separate out carbide once aged at 400℃for a short time, and the property is seriously embrittlement, the optimum aging temperature for high manganese steel crossing is 350℃.During deformation aging, firstly low temperature recovery is taken place in deformation high manganese steel and its hardness vale decreased , and then precipitation decomposition is taken place , its hardness vale increased and decreased again. During strain induced aging, high manganese steel separate out carbide in the conditions of 1800MPa contact stress and 100℃for 40 hours, and precipitation decomposition is accomplished. In the process of aging of high manganese steel, the temperature of accomplishing precipitation decomposition is gently decreased with additional mechanical energy increased. Meanwhile another results shows that, the main work hardening mechanism of high manganese steel in compressed state is twins work hardening .The temperature rising of high manganese steel crossing work surface during service is about 150℃. The rolling contact fatigue life of high manganese steel used for crossing is about 1.2×106 cycles under 1800MPa contact stress, the overload quantity is 5Mt which is much lower than that of practical high manganese steel crossing. The contact surface is failed by means of fatigue spalling.The hardened layer is only depth of 1.5mm and the maximum hardness vale is about 700HV.更多还原