铁路机车用51CrV4弹簧失效分析

Failure Analysis on 51CrV4 Spring For Locomotive

采用化学成分分析、组织观察和硬度测试等分析方法,对铁路机车用51CrV4弹簧进行失效分析。结果表明:断簧的化学成分、非金属夹杂物级别和金相显微组织均符合技术规范要求。但弹簧的强度、断口处硬度及疲劳源附近残余压应力值偏低,且存在全脱碳层。此外,弹簧支撑圈和工作圈间因反复接触产生的压痕破坏了表面完整性,易于引发应力集中而导致弹簧疲劳裂纹萌生。在这几个因素综合作用下,弹簧在高频交变应力作用下产生裂纹导致早期疲劳断裂失效。

The fracture failure of 51CrV4 spring for locomotive was analyzed by chemical composition analysis, structure examination and hardness testing. The results show that the chemical compositon of fxactured spring, the grades of the non-metallic inclusions and the microstructure meet the requirements of the technical specification. The strength of the spring, hardness near the fracture and the residual compressive stress near fatigue source are lower, while, there is complete decarburization layer on the surface of the spring at the same time. Moreover, the indentations caused by repeated exposure between the surpport ring and the workable coils can damage the surface integrity, which is easy to produce stress concentration and lead to the initiation of the fatigue crack. Under the action of these comprehensive factors, the appearance of the crack in spring under the high frequency alternating stress can result in early fatigue fracture failure.