Fracture Analysis on Drill Pipe Hanger of Gas Well

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.