Abstract
As reported in the previous papers, the high current AC-MIG welding process has been successfully applied to butt welding of sheared plates in a steel pipe mill. The author has improved the AC-MIG process to a further high efficient one that employs two electrodes in tandem providing one molten weld pool. An attempt has been made to apply this improved process to seam welding of UO pipes for the frigid zone use together with a SAW process.
It has been found that the new process gives deep penetration exceeding 5 mm in the root pass and sufficiently melts grooves to provide wide weld beads so that 1 m/miri welding velocity two times higher than that by the previous processes can be obtained even under highly varying groove width conditions.
