某单相断路器连杆的断裂原因

Failure Cause of Link of a Single-Phase Circuit Breaker

某批单相断路器4Cr13钢连杆在调试试验中发生断裂,结合连杆的加工过程,用光学显微镜、扫描电子显微镜和维氏硬度计对其断裂原因进行了分析。结果表明:4Cr13钢连杆在90°弯角内侧发生脆性过载断裂,断裂形式为准解理断裂;4Cr13钢连杆在90°弯角内侧的硬度偏高,同时倒角圆弧半径偏小,使其在弯型过程中于90°弯角内侧发生应力集中而形成微裂纹,并最终导致4Cr13钢连杆在调试过程中因受力而发生断裂;合理设计连杆结构,并在弯型工序前控制退火过程中的加热速率,可避免4Cr13钢连杆发生断裂。

4 Cr13 steel links of a batch of single-phase circuit breakers fractured during debugging.The reason for fracture was analyzed by optical microscope,scanning electron microscope and Vickers hardness tester,combining with manufacturing process of links.The results show that the brittle over-load fracture of 4 Cr13 steel links occurred inside the 90°corner,and the fracture mode was quasi-cleavage fracture.The hardness at inner side of90°corner of 4 Cr13 steel links was relatively high,and the radius of chamfering fillet was small,resulting in the stress concentration inside the 90°corner of links during bending.And then the microcracks formed,leading to the fracture of 4 Cr13 steel links due to the force during debugging finally.The reasonable design of link structure and controlling the heating rate of annealing process before bending process could avoid the occurrence of fracture of links.