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从化学成分、硬度、断口宏观形貌、显微组织等对断裂失效的D20发动机连杆螺栓进行了分析。结果表明,发生在螺纹处断裂的螺栓是由于热处理后滚丝成型不当造成表面加工缺陷,在交变载荷的作用下,产生微裂纹,进而至螺栓完全断裂;在头部支承面处断裂的螺栓因无圆角过渡、加工制造粗糙,在交变载荷的作用下,发生应力集中,致螺栓断裂。建议严格控制热处理工艺过程,提高螺栓加工精度。
From the chemical composition, hardness, fracture morphology, microstructure fracture failure of the D20 engine connecting rod bolts were analyzed. The results show that the bolts that break at the thread are caused by surface processing defects caused by improper thread rolling after heat treatment. The microcracks generate under the action of alternating loads and the bolts are completely broken. The bolts broken at the head support surface Because there is no fillet transition, manufacturing rough, under the action of alternating load, stress concentration, resulting in bolt fracture. It is recommended to strictly control the heat treatment process and improve the bolt processing accuracy.