微观组织对车轮钢力学性能和磨损性能的影响研究

燕青芝 车延婧 洪志远

摘 要：车轮钢和轨道钢的微观组织和力学性能对高铁运行的安全性和服役寿命具有决定性影响。该工作采用淬回火和淬火雾冷两种热处理制度制备了具有等轴状铁素体和粒状渗碳体的回火索氏体车轮钢和片状渗碳体分布在铁素体中的索氏体车轮钢。通过优化热处理制度，两种钢的晶粒均在7级，属于细晶组织。对两种组织的钢进行伸试验，两种钢的拉伸强度大于900 Mpa，延伸率大于15%；由于淬回火车轮钢中颗粒渗碳体的弥散强化作用，其强度比淬火雾冷的车轮钢更高。夏比冲击试验表明，在室温下淬火雾冷的车轮钢冲击吸收功高于淬回火车轮钢，但随着冲击温度的降低，淬火雾冷的车轮钢冲击功幅度下降幅，而淬回火钢一直到-20℃韧性几乎不降低。模拟高铁载荷和时速500 km运行下轮轨接触频率，将两种钢与相同轨道钢配副做滚动接触疲劳试验。结果表明：淬回火车轮钢的疲劳寿命更长，裂纹的萌生主要发生在试样的表面和亚表面夹杂物或应力集中处，在表面萌生的裂纹一般会沿一定的角度向内部扩展，然后沿平行于试样表面进行扩展，最后从试样上撕裂下来。裂纹扩展一般沿着夹杂物与基体界面进行；当夹杂物阻碍裂纹前进时，裂纹会绕过夹杂继续扩展。在摩擦之后，车轮轨与轨道钢的硬度都有1～2HRC的硬度下降，组织成分由于发生了再结晶及塑性变形下，条带状碳化物被碾碎等因素，使其与原始组织有了很大的不同。在硬度为34HRC左右时有最好的抗摩擦性能。

关键词：高铁车轮钢 微观组织 力学性能 滚动接触疲劳

Abstract：The increasing of high-speed train speed puts forward higher requirements on wheel and rail materials. Microstructure and mechanical properties of high-speed wheel and rail steel have a great influence on the safety， comfort of trains. At high speed， the rolling contact fatigue of wheel steel problem is more prominent， becoming major injury problems of wheel material. According to the requirements of wheel and rail steel， this article developed heat treatment system for them and carried out the research work about the regular pattern on rolling contact fatigue crack initiation and expansion. By the experiments， the main research results obtained are as follows：（1）Two suitable heat treatment patterns for new high speed wheel and rail steel：①for wheel steel， one pattern is quenching at 860℃ and tempering at 530℃， the other is quenching at 860℃to about 650℃， then water spray cooling to ambient temperature；②for rail steel， one pattern is quenching at 820℃ and tempering at 580℃， the other is hold at 820℃， then water spray cooling to ambient temperature.（2）Finer grain both can be obtained by two different heat treatment patterns. Tempered sorbite is obtained by quenching and tempering， sorbite is obtained by quenching and water spray cooling for wheel steel and by water spray cooling for rail steel.（3）Comprehensive properties of heat treated wheel steel are better than as-received while steel， and the quenched and tempered wheel steel is better than quenched and water spray cooled while steel.（4）According to the results from rolling contact fatigue， the crack initiation occurs in surface and sub-surface where stress concentration at， and the crack usually extends along the interface between the inclusions and the matrix.（5）The hardness of wheel and rail steels decreases by 1～2 HRC after being rubbed， in the condition of recrystallization and plastic deformation， the composition become extremely different with the original structure because of the crush of banded carbide. As a conclusion， we can say that the material has the best anti friction performance when the hardness is about 34HRC.

Key Words：Wheel steel of high-speed train；Microstructure；Mechanical properties；Rolling contact fatigue

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