S135钻杆管体刺穿失效分析

Piecing Failure Analysis of S135 Drill Pipe Body

通过宏观分析及材料理化性能分析测试,并结合断面微观分析,对某S135钻杆管体刺穿失效原因进行了分析。结果表明:钻杆刺穿失效的主要原因是热处理工艺不当,使得钻杆外表面形成脱碳层,降低了其力学性能,在钻井过程中复杂的交变应力载荷作用下,钻杆表面腐蚀坑底部首先形成微裂纹并迅速扩展,最终导致钻杆发生早期疲劳失效。

Failure causes of S135 drill pipe were investigated through visual morphology analysis, mechanical property test, and fracture analysis. Results show that the decarburized layer on its out-surface caused by improper heat treatment is the mainly failure reason of the drill pipe body, which decreases its mechanical properites. Under the effect of alternating stresses, the crack is firstly initiated in the bottom of corrosion pit and extended quickly. In the end, it leads to early fatigue failure in the drill pipe.