GIS操作机构用止锁凸轮开裂失效分析

王晓生 史润军 张明英

摘 要：某单位产品更新换代前，在验证操作机构性能时出现异常报警，经检查发现，该机构止锁凸轮断裂损坏。本文采用宏观断口分析、化学成分分析、硬度检测、金相检验、扫描电镜分析等方法对断裂的原因进行了分析。结果表明：原材料呈带状分布的偏析带，在热处理淬火时极易产生微裂纹;热处理不当破坏了凸轮“外硬内韧”的状态，凸轮整体呈脆性，这两个因素最终造成止锁凸轮发生沿晶脆性断裂。

关键词：止锁凸轮;带状偏析;应力集中;沿晶脆性断裂

中图分类号：TG115.28文献标识码：A文章编号：1003-5168（2021）08-0065-04

Failure Analysis of Locking Cam Used in GIS Operating Mechanism

WANG Xiaosheng SHI Runjun ZHANG Mingying

（Henan Pingzhi High Voltage Switch Co.， Ltd.，Pingdingshan Henan 467013）

Abstract： Before the replacement of unit product， an abnormal alarm occurred when the performance of the operating mechanism was verified， and it was found that the locking cam of the mechanism was broken and damaged. In this paper， macro fracture analysis， chemical composition analysis， hardness testing， metallographic examination， scanning electron microscope analysis and other methods were used to analyze the causes of fracture. The results show that the raw materials were banded segregation bands， which were easy to produce microcracks during heat treatment and quenching; Improper heat treatment destroys the "hard outside and tough inside" state of the cam， and the whole cam was  brittle. These two factors eventually led to intergranular brittle fracture of the locking cam.

Keywords： stop locking cam;belt segregation;stress concentration;brittle fracture along

1 研究背景

某單位产品更新换代前，在验证气体绝缘金属封闭开关设备（Gas Insulated Switchgear，GIS）操作机构性能时出现异常报警，连续操作中断。经检查发现，该机构止锁凸轮开裂损坏，如图1所示。

该凸轮材料为42CrMo耐热钢。42CrMo耐热钢属于中碳低合金结构钢，具有较高的强度、韧性以及良好的淬透性，淬火变形小，在高温下仍有较高的蠕变强度和持久强度。42CrMo耐热钢一般在调质热处理后试验，调质后的组织为均匀细小的回火索氏体，具有较好的综合力学性能，疲劳强度高，抗冲击性能好，没有明显的回火脆性等。42CrMo耐热钢被广泛用于制造起重机承重轮、汽车曲轴、连杆及发动机气缸等[1-3]。

止锁凸轮的生产工艺流程为：原材料→下料→粗机械加工→半精机械加工→调质热处理→精加工→碳氮共渗。42CrMo耐热钢经过调质、碳氮共渗后获得显微组织表面为细马氏体、残余奥氏体和碳化物，心部组织为回火索氏体。……