65Mn钢波形垫圈断裂分析

Fracture Analysis of 65Mn Steel Wavy Washers

本文从化学成分、显微组织、断口形貌、氢含量、硬度等方面,对表面镀镉65Mn钢波形垫圈使用过程中连续出现早期断裂的原因进行了分析。对同批零件进行了氢脆和回火脆性验证试验,分析了除氢时间、氢含量、硬度以及回火温度对断口形貌的影响,同时对不同硬度检测方法对垫圈硬度值的影响进行了分析。结果表明,硬度测量方法选择不当导致波形垫圈的实际硬度超出技术要求,使波形垫圈脆性增加,引起波形垫圈最终断裂,残余氢导致断口呈沿晶特征。建议将该波形垫圈回火温度控制在380～410℃范围内,选择HV5.0或HV10检测硬度,除氢时间不低于12h。

65Mn steel wavy washers fractured in the early stage of service. The fracture cause of the wavy washers was analyzed by chemical composition analysis, microstructure and fracture appearance observation, and hydrogen content and hardness testing. The influence of dehydrogenation time, hydrogen content, hardness and temper temperature on the fracture appearances was analyzed by hydrogen brittleness and temper brittleness confirmatory tests. In addition, the influence of hardness testing methods on the measured hardness values was analyzed. The results show that improper hardness testing methods resulted in higher actual hardness values, above the specification, and the increase of the brittleness. As a result, the wavy washers fractured finally, and the residual hydrogen resulted in the intergranular feature of the fracture surfaces. It is suggested that the temper temperature should be higher than 380℃ and lower than 410℃, HV50 or HV10 should be chosen to test hardness, and the dehydrogenation time should be longer than 12 hours.