某油田生产井油管短节发生断裂,采用宏观观察、化学成分分析、金相检验、力学性能测试、扫描电镜和能谱分析等方法对其断裂原因进行分析。结果表明:镦粗工艺和结构特征导致短节的力学性能不均匀,且在腐蚀性介质的作用下,短节内壁产生微小腐蚀坑并萌生裂纹;在环境和载荷的共同作用下,裂纹发生扩展,最终导致材料的剩余强度不足,使短节发生断裂。

The tubing joint of a production well in an oilfield was fractured. The fracture reason was analyzed by means of macroscopic observation, chemical composition analysis, metallographic examination, mechanical property test, scanning electron microscope and energy spectrum analysis. The results show that the upsetting process and structural characteristics led to the uneven mechanical properties of the joint, and the inner wall of the joint produced tiny corrosion pits and initiated cracks under the action of corrosive medium. Under the combined action of environment and load, the crack propagated and eventually led to the insufficient residual strength of the material, then the joint cracked.