钻杆内螺纹接头纵裂与刺穿失效分析

针对某油田一批进口钻杆连续发生１７根钻杆内螺纹接头纵向开裂和刺穿事故，对断口进行Ｘ射线能谱、电镜和金相分析，并采样进行机械性能试验分析，认为材料不是导致接头断裂的主要原因。对断口裂纹源和内螺纹接头综合分析，认为接头连接后，在内螺纹尾部形成的凹槽区钻井液流动比较困难，使凹槽区螺纹缝隙内的氢离子浓度增加而容易产生缝隙腐蚀，腐蚀反应产生的氢沿内、外螺纹连接后的螺旋空间进入螺纹连接之间的表面，继而进入材料中，诱导材料的氢脆敏感性，最后导致材料的氢脆开裂。钻杆在使用过程中，过扭矩使螺纹连接的切向拉应力大幅度增加也促进了接头的氢脆开裂。

Failure analysis of drill pipe box

In the light of the successively occurred piercing and longitudinal cracking on the drill pipe boxes,the fractures are analyzed by X-ray energy spectrum and electronic microscope,and the mechanical properties of the material are tested.The result of the analysis and test shows that the property of material isnot the main factor causing foe failure.Analysis shows that there is a groove area at the thread end of the drill pipe box,where the concentration of the hydrogen ion increases in the thread crevice due to the im peded circulation of the drill fluid,resulting in the so-called crevice corrosion,and the hydrogen produced by the corrosion action iutrudes into the material,inducing hyprogen embrittlement and therebycausing hydrogen brittle cracking of the material.