某批SWRCH15A钢螺钉在装配使用一个星期后，有10件螺钉发生自然断裂。通过宏观检验、金相检验、硬度及渗碳层深度测试、断口分析的方法，分析了螺钉断裂的原因。结果表明：在该批螺钉的电镀锌过程中，溶液中存在H+和H2O分子，促使发生阴极反应析出的氢原子富集，诱发阴极氢脆型应力腐蚀，从而造成螺钉的延迟断裂。

The natural fracture happened to SWRCH15A steel screws after installation and use for one week. Through the methods of macroscopic examination, metallographic examination, hardness and carburized case depth testing, and fracture analysis, fracture reasons of screws were analyzed. The results show that during the process of zinc electroplating, the H+ and H2O existed in the solution caused the cathodic reaction and the precipitated hydrogen atoms gathered. It induced the stress corrosion of cathodic hydrogen embrittlement, and finally resulted in the delayed fracture of the screws.