摘要
某井发生钻铤内螺纹接头横向开裂失效。进行了宏观分析、力学性能测试、化学成分分析、金相组织和微观断口分析,结果表明,钻铤材料中MnS夹杂物超标,螺纹底部和牙侧存在腐蚀坑和加工划痕,这些缺陷的存在降低了钻铤的服役能力;钻铤接头应力减轻槽加工不符合标准要求,致使内螺纹接头螺尾根部成为螺纹连接的薄弱部位,在交变应力作用下,应力集中的螺尾根部萌生裂纹并疲劳扩展,导致钻铤接头横向开裂。
Failure reason of drill collar box was studied through visual inspection,mechanical properties test,chemical composition analysis,metallographic examination and fracture surface analysis.Results showed that MnS inclusion wasn＇t in accordance with standard,and there were lots of corrosion pits and mechanical defect in root and flank,witch decreased life of drill collar box.Stress-relief structure was not in accordance with related standard,witch leaded washout thread＇s root to be the weakest situation of drill collar box.Under the effect of alternating stresses,cracks initiated from root of washout thread and developed quickly.In the end,they leaded the drill collar box to early fatigue failure.
出处
《石油矿场机械》
2010年第11期44-48,共5页
Oil Field Equipment
关键词
钻铤
疲劳
螺尾
失效分析
drill collar
fatigue
washout thread
failure analysis
