通过化学成分分析、断口分析、金相检验和扫描电镜观察等方法, 对42MnMo7钢地质钻杆的断裂原因进行了分析。结果表明: 钻杆在交变力作用下, 在螺纹根部的应力集中处产生裂纹, 此裂纹在过载力和钻杆基体存在带状脆性马氏体的情况下进一步扩展, 最终导致钻杆发生断裂。最后对此提出了相应的措施及建议。

The fracture reason of 42MnMo7 drill pipe was analyzed by means of chemical compositions analysis, fracture analysis, metallographic examination and scanning electron microscopy(SEM) observation. The results showed that drill pipes were effected by the alternate stress, making the cracks initiated on the bottom of thread stress concentrated, meanwhile the martensite layer in the pipe body reduced the toughness and plasticity, which made the crack propagate, and eventually the drill pipe was fractured. And the corresponding solutions and suggestions were proposed.