Solidification Cracking of Longitudinal Submerged Arc Welded Pipes

摘要

High-strength longitudinal submerged arc welded (LSAW) pipes are used by the oil and gas operators for long-distance fluid transfer. During manufacturing of 18-m-long LSAW pipes, numerous T-end (Tail end) cracks were observed by manual ultrasonic testing. A failure investigation was carried out on weld crack formed approximately 40-150 mm away from T-end of a 762 mm OD x 15.8 mm WT x 18,000-mm-long API 5L X70M grade pipes. The present paper discusses the analysis of end cracks with the help of NDT, microhardness, metallography, SEM and EDS analyses and possible factors responsible for the T-end cracks. The high strength of parent material, a longer length of the weld seam and transverse displacement were observed as the possible causes for the formation of solidification cracks at one end of LSAW pipes.