钻铤内螺纹接头开裂失效分析

摘要

通过宏观分析、力学性能测试、化学成分分析、金相组织和微观断口分析，对某井发生的钻铤内螺纹接头开裂失效原因进行分析。结果表明，钻铤规格和螺纹型号匹配不当降低了钻铤的服役能力，在服役过程中交变应力载荷作用下，应力集中最为严重的最后旋合螺纹根部萌生疲劳裂纹并扩展，最终致使钻铤接头开裂失效。%Failure reason of drill collar box was researched through visual inspection, mechanical properties test, chemical composition anal-ysis, metallographic examination and fracture surface analysis. Results showed that the mismatch of drill collar and thread decreased the drill collar’s service ability. During the drilling process, under the effect of alternating stress loads, fatigue crack initiated and propagated fast from thread root, and eventually caused the cracking failure of drill collar.