42CrMo钢曲轴坯料的大斑缺陷分析

Analysis of large spot defects in 42CrMo steel crank shaft blank

针对42CrMo钢曲轴坯料中出现的大斑缺陷,采用形貌观察、断口、扫描电镜及能谱分析确定缺陷是以碳元素为主的成分偏析;结合生产及缺陷的形成过程,提出电渣冶炼气氛中水分控制办法。对比试验缺陷试样及合格试样的力学性能、弯曲旋转疲劳及扭转。结果表明,在屈服强度R_(p0.2)为950 N/mm^2时,缺陷试样的屈服强度R_(p0.2)低9%,弯曲疲劳极限低5%,扭转强度极限τm及τ_(p0.2)低3%。

The reason for large spot defects in 42 CrMo crank shaft blank was studied by means of morphology observation,scanning electron microscope and energy spectrum analysis.The results show that the defects are caused by carbon segregation.Combined with the production process and the formation process of defects,the control method of water in atmosphere during ESR was put forward.The actual integrated performance of the product was also studied at the yield strength R_（p0.29）50 N/mm^2.The results show that compared with qualified specimen,the yield strength R_（p0.2） of the sample with defects is 9% lower than that of qualified specimen,the bending and rotating fatigue is 5% lower,the torsion fatigue is 3% lower.