Butt welding of thick, high strength steel plate with a high power laser and hot wire to improve tolerance to gap variance and control weld metal oxygen content

This study, which pertains to the butt welding of 590 MPa high strength steel plates with a high power laser over gaps, was conducted to investigate weld penetration characteristics, to clarify welding phenomena, and to develop procedures for obtaining high quality joints. Butt welding was performed on 12 mm thick plates with a 16 kW high power disc laser together with a hot wire. In this way, welding defects are suppressed and weld metal oxygen content is controlled, thereby producing sound, fully penetrated welds. Penetrations were stable over a range of gaps from 0 to 0.4 mm, owing to an ejection of excess melt through a keyhole outlet at the bottom of the molten weld pool by a strong plume. Here, the use of a hot wire together with a laser of sufficient power to produce a fully penetrated keyhole was effective in improving the gap tolerance and suppressing oxygen inclusion within the butt weld.