Study of all position electron beam welding process for pipeline joints

Abstract

For the purpose of applying the electron beam (EB) welding process to the site welding of natural gas pipelines, the authors investigated fundamental all position EB welding characteristics for 19 mm thick API 5L–X65 steel pipe. To establish appropriate welding conditions for satisfactory weld bead formation, the study was separated into two steps. First, appropriate welding parameter ranges were investigated in eight representative welding positions by rotating the test pipe in which the electron gun was fixed. Second, based on the investigation in the first step, all position continuous welding was carried out successfully by rotating the gun in a vertical plane. The influence of edge misalignment and mismatch on weld bead formation was investigated and the dimensional tolerances needed to obtain acceptable weld beads were clarified. Solidification cracking in the weld metal of a pipeline steel was investigated and it was determined that sulphur was the most harmful element in terms of promoting cracking. Some mechanical properties of the weld joint were also examined.