220 kV断路器合闸缓冲器滚子轴承断裂失效分析

Fracture Analysis of Roller Bearing in Closing Buffer of 220 kV Circuit Braker

某220kV断路器合闸缓冲器滚子轴承在合闸操作过程中发生碎裂,本文利用体式显微镜、扫描电子显微镜(SEM)观察了滚子轴承断口形貌,利用X射线荧光光谱对滚子轴承外侧表面化学成分进行了分析,利用硬度测试仪分别对轴承外表面、截面中心和内表面进行了硬度检测,利用金相显微镜(OM)对轴承微观组织进行了分析,通过有限元仿真软件对滚子轴承受冲击过程进行了模拟。结果表明:该合闸缓冲器滚子轴承断裂的主要原因是轴承在渗碳淬火热处理后表面硬度偏高而截面中心硬度偏低,造成表面硬脆而中心冲击韧性较差。在受到凸轮冲击时轴承表面破碎和内部塑性变形,导致凸轮、轴承与滚子卡涩,机构动作载荷完全加载在卡涩的轴承外壳上,最终使整个轴承碎裂。

The roller bearing in the closing buffer of a 220 kV circuit braker fractured during the closing operation.In this paper,the fracture morphology of the roller bearing was observed by stereomicroscope and scanning electron microscope(SEM).The chemical composition of the outer surface of the roller bearing was analyzed by X-ray fluorescence spectroscopy.The hardness of the outer surface,the center of the cross section and the inner surface of the bearing was measured by hardness tester.The microstructure of the bearing was analyzed by optical microscope(OM).The impact process of the roller bearing was simulated by finite element simulation software.The results show that the main reason for the fracture of the roller bearing of the closing buffer is that the surface hardness of the bearing is high and the hardness of the cross section center is low after carburizing and quenching heat treatment,resulting in a hard and brittle surface and poor impact toughness of the center.When impacted by the cams,the surface of the bearing is broken and the internal plastic deformation occurs,resulting in the locking of the cams,the bearing and the roller.The action load of the mechanism is completely loaded on the locking bearing shell,and finally the whole bearing is broken.