Hot-wire Laser Welding Process Using Laser Diode for Large-Diameter Pipe with Narrow Gap Joint

We investigated a hot-wire laser welding method using a laser diode with a rectangular laser beam to weld a large-diameter pipe with a narrow gap. First, welding trials using plate specimens were performed to obtain the optimum welding conditions using a defocused beam. We achieved stable feeding of wire, a stable molten pool, and a well-formed weld bead, with few defects. Second, we welded a large-diameter pipe using optimum welding conditions discovered from the trials. Although some small lack of fusion occurrences were observed in the side bending test, we achieved a narrow gap, low dilution, narrow heat-affected zone weld without solidification cracks.