某导弹发射架在进行第3次动载荷试验过程时,其上的一件42CrMo外六角高强度螺栓出现了断裂;通过对断口进行宏微观检查、电镜观察、金相组织检查、硬度检查及化学成分分析,确定了零件的断裂性质和断裂原因.结果表明:螺栓的断裂性质为原始裂纹引起的应力腐蚀断裂.由于螺栓在镀锌前存在原始微裂纹,造成了应力集中,并在随后的镀锌过程中出现了腐蚀现象;在试验过程中,由于弯曲应力和大气环境中氧、硫、氯、钠等腐蚀介质的共同作用,导致了螺栓的断裂.另外零件硬度值偏高,存在轻微的回火脆性,对断裂也有一定的影响.
When the missile launcher was carried out during the third test procedure,fracture occurred to the 40CrMo bolt.In this paper,investigations were performed by macroscopic examination,electron microscope observation,metallographic examination and chemical composition analysis in order to get the fracture property and the reason of the fracture.The results suggest that the property of fracture is stress corrosion,as well as the original micro-cracks in the bolt before galvanizing and lead to stress concentration.During the test,the existence of bending stress and atmospheric oxygen,such as sulfur,chlorine,sodium and other interaction,which result in fracture of the bolt.Furthermore,high hardness values and a slight temper brittleness can also have a certain effect on the bolt fracture.
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