感应淬火对曲轴扭转疲劳性能的影响

Effect of Induction Hardening on Torsion Fatigue Property of Crankshafts

目的研究感应淬火对曲轴扭转疲劳性能的影响,为曲轴的设计和制造工艺调整提供技术参考。方法开展淬火曲轴和未淬火曲轴的扭转疲劳强度试验,利用升降法得到疲劳试验结果,从试验数据和微观组织等方面开展分析和讨论。结果未经过淬火的曲轴在99.9%存活率下的扭转疲劳极限为967.6N·m,经过感应淬火的曲轴在99.9%存活率下的扭转疲劳极限为1361.2N·m。感应淬火后曲轴的表面形成深度约3.5 mm的淬火层,平均硬度为HV0.5600,金相组织为细针状马氏体。曲轴的失效情况均为连杆颈油孔处开裂。结论 38MnVS6非调质钢曲轴在感应淬火后的扭转疲劳极限提升了约41%,曲轴油孔内壁的加工缺陷是形成裂纹源的主要原因,对曲轴淬火层区域的油孔内壁进行一定的表面处理,可进一步提高曲轴的扭转疲劳强度。

This paper aims to study the effect of induction hardening on torsion fatigue property of crankshafts and provide technical reference for adjustment on design and manufacture process of crankshafts. The torsion fatigue strength test of hardened crankshaft and unhardened crankshaft was carried out. The results of fatigue test were obtained through the lift method. And the test data and microstructure were analyzed and discussed. The results show that the torsion fatigue limit of unhardened crankshaft was 967.6 N·m at 99.9% survival rate; and that of induction hardening crankshaft was 1361.2 N·m at 99.9% survival rate. After induction hardening, the surface of the crankshaft formed a quenching layer with a depth of about 3.5 mm, with an average hardness of HV0.5600 and fine needle-like martensite microstructure. The failure of the crankshaft was the cracking at the link neck oil hole. The torsion fatigue limit of 38MnVS6 non-tempered steel crankshaft is increased by about 41% after induction hardening. The processing defects on the inner wall of crankshaft oil bore are the main reason for the formation of crack source. The torsion fatigue strength of crankshaft can be further improved by surface treatment of the inner wall of oil hole in the quenching layer of crankshaft.