某8.8级42CrMo钢高强度螺栓，在热处理后滚丝过程中发生轴向开裂。利用化学成分分析、宏观检验以及金相检验等方法对螺栓开裂原因进行了分析。结果表明：螺栓开裂主要是因为其原材料表面存在呈线状分布的锻造折叠缺陷，折叠缺陷末端形成应力集中，在热处理淬火时成为了裂纹源，于强大的淬火应力和滚压应力作用下诱发了螺栓轴向开裂。

A 8.8 grade high strength bolt made from 42CrMo steel cracked along the axis during thread rolling process after heat treatment and the cracking causes of the bolt were analyzed by means of chemical composition analysis, macro examination and metallographic examination. The results show that the cracking of the bolt was mainly due to that there was linear distribution forging fold defect in the raw material surface before heat treatment. And the forging fold defect caused stress concentration and became a cracking source when quenching, which induced the axial cracking of the bolt under the action of powerful quenching stress and rolling stress.