SWRCH22A钢自攻螺钉在装配一天后发生断裂，通过宏观检验、化学成分分析、金相检验、断口分析及氢含量测试等方法，对其断裂原因进行了分析。结果表明：螺钉的断裂性质为氢致延迟脆性断裂；螺钉经过热处理后的显微组织为回火马氏体和少量残余奥氏体，而马氏体为氢脆敏感组织，且螺钉经过电镀处理，使得其内部氢的质量分数高达0.000 49%，最终导致螺钉于应于集中的螺纹起始位置根部发生氢致延迟脆性断裂。

Fracture occurred to self-tapping screws of SWRCH22A steel after assembly for one day. The fracture reasons were analyzed through macrographic examination, chemical composition analysis, metallographic inspection, fracture analysis and hydrogen content testing. The results indicate that:the fracture mechanism of screws was delayed brittle fracture induced by hydrogen; the microstructure of screws after heat treatment was mainly tempered martensite and a small amount of residual austenite, and the martensite structure was sensitive to hydrogen brittle; the screws were treated by electroplating, which made the hydrogen content of screws as high as 0.000 49%, and finally caused the delayed brittle fracture of screws induced by hydrogen on the root of thread initiation position where the stress concentrated.