某油田天然气井的钻杆悬挂器(套筒)在使用过程中发生断裂失效事故, 采用化学成分分析、金相检验、硬度测试、断口分析、微区成分分析等方法对断裂件进行了分析。结果表明: 该1Cr13钢悬挂器淬火后未经高温回火, 不符合调质热处理工艺的技术要求。基体中的淬火马氏体组织硬度过高, 残余内应力大, 沿晶界及亚晶界聚集分布的颗粒状未溶碳化物(Fe, Cr)23C6降低了钢的抗蚀性。该套筒内联上接头的螺纹部位薄壁存在周向拉应力, 使用时在高压天然气作用下, 筒壁沿圆周方向附加有横向拉应力。套筒内部环境为湿硫化氢的天然气介质, 结果导致该悬挂器沿纵向产生应力腐蚀断裂。

The natural gas pipe hanger (sleeve) of an oilfield was fractured in use. By means of chemical composition analysis, metallographic examination, hardness testing, fracture analysis, micro component analysis and so on, the fracture reason was analyzed. The results showed that the hanger sleeve of 1Cr13 steel was not high temperature tempered after quenching, that did not meet the technical requirements. The corrosion resistance of steel was reduced because of the high hardness of the quenching martensite in base metal, the high residual stress and the granular undissolved carbides (Fe,Cr)23C6 distributed along grain boundary and sub-grain boundary. There was circumferential tensile stress in the thin wall of sleeve joint thread, under the effect of high pressure of natural gas, the transverse tensile stress was added along the circumferential direction of tube wall. The internal environment of wet hydrogen sulfide gas medium resulted in stress corrosion cracking along the longitudinal hanger.