免退火CH35A-M冷镦钢螺栓开裂原因分析

Causes for Cracking of Bolt Made of SCM35A-M Cold Heading Steel Free from Annealing

采用免退火CH35A-M冷镦钢制作的六角头螺栓调质处理后发现有个别开裂。对开裂螺栓进行了宏观检验、金相检验和断口分析。结果表明:螺栓无明显缺陷,裂纹两侧无脱碳现象,但断口被氧化成黑色。据此可以断定,螺栓淬火开裂是可能存在机加工缺陷所致。

Individual hexagonal head bolt,made from CH35A-M cold heading steel free from annealing,was found cracking after quenching and high temperature tempering.The cracked bolt was subjected to macro check,metallographic examination and fracture testing.The results showed that the bolt had no obvious defect,and there was no decarburization phenomen on both sides of crack,but the fracture was oxidized to become dark.From these it was concluded that the bolt cracking in the process of quenching was attributed to possible presence of machining defects.