螺杆钻具传动轴断裂原因分析

Fracture Cause of Screw Drill Drive Shaft

某油井进行钻进作业时,螺杆钻具的传动轴半环发生断裂并落井。通过宏观分析、化学成分试验、力学性能检测、金相试验、扫描电镜(SEM)及能谱分析,对断裂失效原因进行了分析。试验及分析结果表明,该螺杆钻具传动轴断裂失效的主要原因是该传动轴外表面存在大量裂纹,在旋转弯曲应力作用下,从外表面裂纹处启裂,在交变载荷和Cl-作用下,裂纹快速扩展并导致最终断裂失效。

During the drilling operation of a well,the half ring of the drive shaft of the screw drill was broken and fell into the well.The reason of fracture failure is analyzed by means of macro analysis,chemical composition analysis,mechanical properties testing,metallographic analysis,scanning electron microscopy(SEM)and energy spectrum analysis.The results show that the reason of the fracture failure is that there are many grinding cracks on the outer surface of the drive shaft.Under the action of rotating bending stress,the crack starts from the grinding crack,and then with the action of alternating load and Cl-,the crack propagates rapidly and finally leads to fracture failure.