汽车发动机气门弹簧断裂原因分析

汽车发动机气门弹簧发生断裂。通过对气门弹簧进行宏观检查、硬度检测、金相组织检测、化学成分检测、断口分析、能谱分析,以查找、确定发动机气门弹簧疲劳断裂性质及产生原因。结果表明:气门弹簧断裂性质为疲劳断裂,导致弹簧发生疲劳断裂的直接原因是表面麻坑缺陷,表面麻坑在原材料钢丝状态时已经存在。通过在卷簧机器前增加自动识别钢丝表面缺陷装置、增加检测频次等一系列的改进措施,该问题得到预防。

Failure Analysis of Valve Spring in Automobile Engine

The valve spring in an automobile engine fractured. The present work aims to identify the failure mode and cause by visual inspection, hardness measurement,metallurgical analysis, chemical composition analysis, fracture appearance observation, and EDS analysis. The results show that the fracture mode of the valve spring is fatigue fracture. The direct cause of fracture is that there are pits at the surface of the valve spring. The pits had existed when the spring was in the form of steel wire. Based on the results, the valve spring supplier has conducted improvement measures, including adding an automatic recognition system of pits before spring coiling machines and increasing the measurement frequency. After that, the problem of fracture of valve spring has been effectively solved.