R95钢级外加厚油管断裂失效分析

Analysis of Fracture Failure of R95 Externally-upset Tubing

某油管服役3年后发生了断裂失效,分析了其断裂失效的原因。结果表明:此次失效油管承受较大的沿管体纵向的拉应力,并且现场采集的放喷液也检测出大量S^(2-),再加上R95钢级油管材质本身也具有硫化物应力腐蚀开裂的敏感特性,三者结合作用导致硫化物应力腐蚀开裂;另外从硬度分析可以看出油管实测强度、硬度较高,一般来说,随着强度、硬度增加应力腐蚀开裂敏感性增加,所有这些因素增大了硫化物应力腐蚀开裂风险;最后提出了酸性环境使用的管材应尽量选择专用管材,加强酸性环境使用管材的质量把控等建议。

Analyzed here in the paper are the causes for the fracture failure of a certain piece of tubing that has been used for three years.The following facts concerning the failure are revealed via the analysis.The failure tubing is loaded with the tensile stress along the longitudinal direction of the pipe body;so much S^(2-)is found in the blowout liquid as collected on the operation site;and moreover the material of the R95 tubing itself has the SSC-caused fracture sensitive characteristic.As a result,the combined effects by the above mentioned three elements leads to the SSC fracture of the tubing.On the other hand the tubing’s measured strength and hardness via the hardness test are rather high,and in general along with the increases of the strength and the hardness,the SSC fracture sensitivity of the material is getting higher and higher.Conclusively speaking,all the elements as mentioned here get the SSC fracture risk increased.Accordingly it is suggested to select as far as possible specialty tubular goods for service under acidic conditions,and to improve the quality control of the tubular goods as used under the acid conditions.