激光相变硬化对亚共析钢接触疲劳的影响

发布时间：2017-12-28 00:24

本文关键词：激光相变硬化对亚共析钢接触疲劳的影响　出处：《南京航空航天大学》2016年硕士论文　论文类型：学位论文

【摘要】：高速列车行驶过程中,车轮与钢轨的型面匹配极其重要,型面不匹配会产生振动、噪声,影响列车运行的平稳性、舒适性,甚至影响安全性。在型面匹配的条件下,轮缘磨损和踏面疲劳是车轮失效的主要原因。由于轮缘与轨侧磨损主要是滑动磨损,通常要比踏面磨损严重,为了达到型面匹配,需进行定期的镟修,少量的轮缘镟修往往伴随大量的踏面镟修,仅仅轮缘的磨损却导致基本完好的踏面也要被车削掉,造成了极大的浪费。激光相变硬化工艺加热及冷却速度极快,生成的马氏体组织晶粒细小、位错密度高,使相变硬化层具有比常规淬火更高的硬度,零件内部的材料也能保持原有的韧性,大量研究表明,激光相变硬化可以显著提高钢的耐磨性,但是其对轮轨间的滚动接触疲劳影响还有待研究。本文讨论了不同激光相变硬化工艺参数对硬化层组织、硬度、残余应力大小及残余奥氏体含量的影响,以便设计合适的激光相变硬化工艺。对经激光相变硬化处理的车轮钢试样进行摩擦磨损实验以及滚动接触疲劳实验,验证了激光相变硬化工艺对亚共析钢耐磨性及抗疲劳性能的影响。通过X射线应力大小测定、残奥含量测定、显微硬度测量、SEM等分析技术,探究了亚共析钢的滚动接触疲劳机理,并得出了激光相变硬化技术改善亚共析钢抗疲劳性能的原因。采用有限元计算方法,模拟激光相变硬化过程的温度场,并预测大功率激光器可能获得的硬化层深度,为激光相变硬化处理高速列车车轮提供理论依据,通过温度场与相变场的结合,模拟了激光相变硬化层的硬度值。
[Abstract]:During high-speed train running, the matching between wheel and rail surface is very important. Surface mismatch will produce vibration and noise, which will affect the ride comfort, comfort and even safety of trains. The wheel flange wear and the tread fatigue are the main causes of the wheel failure under the condition of the surface matching. Because of the rim and the rail side wear is the main wear, usually tread wear, in order to reach the surface, need regular lathing, small rim lathing are often accompanied by a lot of tread wear repair, only rim has led to the basic well tread will be turning off, cause a great deal of waste. Laser hardening process of heating and cooling speed, the martensite microstructure with fine grains, high dislocation density is generated, the hardened layer is higher than the conventional quenching hardness, parts of the internal material can maintain the original toughness, a large number of studies show that laser transformation hardening can improve the wear resistance of steel, but the the rolling contact fatigue effect between wheel and rail remains to be studied. In this paper, the effects of different laser transformation hardening parameters on hardened layer structure, hardness, residual stress and retained austenite content are discussed, so as to design suitable laser transformation hardening process. The effect of laser transformation hardening process on wear resistance and fatigue resistance of hypoeutectoid steel was verified by friction and wear test and rolling contact fatigue test. The mechanism of rolling contact fatigue for hypoeutectoid steel was investigated by means of X ray stress measurement, residual content determination, microhardness measurement and SEM analysis. The reasons for improving fatigue resistance of hypoeutectoid steel were obtained by laser transformation hardening technology. By using the finite element method, numerical simulation of temperature field during laser transformation hardening, and predict the depth of hardened layer of high power laser may be obtained, for laser hardening and provide a theoretical basis for the high speed train wheel, through the combination of field and phase change temperature field, the simulation of laser hardened layer hardness.
【学位授予单位】：南京航空航天大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TG142.1;TG665

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