某51/2 FH双台肩钻杆内螺纹接头断裂原因分析

摘要

The internal thread joint fracture of drill pipe and the small crack near the fracture of the thread root were analyzed by macroscopic observation, metallographic examination, SEM, EDS energy spectrum. The results showed that the failure of drill pipe is mainly due to the small upper buckle torque, which caused extrusion of the thread surface. Bending at the same time, the thread root bending stress in-creased, then fatigue crack was occurred firstly at the thread root of the drill pipe threaded joint, all of these lead to fatigue failure.%对钻杆内螺纹接头断口及其断口附近螺纹根部的小裂纹采用宏观观察、金相检测、SEM形貌观察、EDS能谱等手段进行分析后认为：该钻杆主要是由于上扣扭矩偏小，造成螺纹面挤压，同时承受弯曲时，螺纹根部弯曲应力增大，使钻杆内螺纹接头在螺纹根部萌生疲劳裂纹，导致疲劳失效发生。