Development of submerged arc welding wire for fabrication of hot bend low-temperature pipeline steel K65 pipe

A NiMoTiB type solid wire was developed for submerged arc welding of hot bended K65 linepipe, and microstructure and mechanical property of the fabricated pipe with a wall thickness of 30.8 mm welded by two-sided four wire submerged arc welding were analyzed and tested. The results shows that the weld metal of as-welded pipe consists of acicular ferrite, a few bainite and M-A constituents, which has a tensile strength of 670 MPa and the impact absorbed energy is no less than 162 J at -40℃. Hot bending process changed the weld metal microstructure into a mix of blocky ferrite and pearlite, while possesses the tensile strength of 665 MPa and impact absorbed energy of no less than 84 J at -40℃.