965 MPa ??????????????????????????

 某油田在商检过程中发现1根965 MPa高强度套管外螺纹接头存在裂纹。通过对该套管进行断口分析、金相分析、力学性能检测、化学元素成分检测，认为套管化学成分和力学性能符合订货技术要求，裂纹是在工厂淬火之前就产生的轧制裂纹。由于该套管母管切定尺管时没有将母管含轧制裂纹的端头彻底切除，在随后加工外螺纹之后进行探伤检验也没有发现该带原始轧制裂纹的套管，致使该含裂纹的套管发给油田。为防止存在裂纹的套管下井，对该批套管逐根进行了探伤检查。建议工厂加强该工序质量检查，并将该工序作为驻厂监造的重点环节之一。

Cause Analysis on Crack of High Strength Casing Pin

It was found during inspection that there was a crack on the pin of 140ksi high strength casing.It is considered that the crack was rolling crack occurred before quenching in mill based on crack and fracture analysis,metallography,mechanical property test and chemical component check.The crack was still in the casing pin because it was not removed from the mother pipe and was not found later during threading and NDT.In order to prevent such casing with crack from running down well,it was inspected for all the casing in the batch.It is suggested that factory should strengthen quality inspection in the working procedure which is also one of the keys for supervision.