某特种产品接套体在黑色磷化后磁粉探伤时陆续发现裂纹，采用宏微观断口分析、X射线能谱分析、金相检验及硬度测试等方法对零件开裂原因进行了分析。结果表明:该特种产品接套体材料为高硬度钢，氢脆敏感性较大;由于该零件在装配时违反了正常工艺流程，先采用油压机装配，装配后才对表尺座燕尾槽部位与孔轴心线的对称度进行校正，该种不正常的操作程序导致校正后零件内孔壁薄板R过渡拐点部位残余应力加大，加上该零件本身内应力较大，从而在随后的酸洗磷化过程中发生氢渗入开裂，形成氢脆裂纹。

Cracks were found in a batch of special products of splicing sleeve bodies when they were magnetic particle inspected after black phosphating, and means such as macro and micro fracture analysis, X-ray energy spectrum analysis, metallographic examination and hardness test were used to analyze the cracking reasons. The results show that the material of the splicing sleeve body was high hardness steel with high hydrogen embrittlement sensitivity. The assembly sequence of the parts violated the normal process, with first assembling by hydraulic machine, and then correcting the degree of symmetry between the dovetail groove and the hole axis. The abnormal assembling procedure increased the residual stress of the inner hole wall sheet R transition position of the parts. At the same time, the internal stress of the part itself was rather high, so hydrogen infiltration cracking happened and hydrogen embrittlement cracks formed during the process of pickling and phosphating.