Bead shape control in high-speed fillet welding using hot-wire GMA laser hybrid welding technology

The weld defects of an undercut and humping bead readily occur in efforts to apply high-speed gas metal arc (GMA) welding for higher productivity. Additionally, weld defects and parameters of the bead geometry such as the flank angle affect the fatigue strength of fillet welded joints. The present study investigated bead shape control for high-speed fillet welding using hot-wire GMA laser hybrid welding technology. First, the effect of hot-wire feeding on the bead formation and molten metal flow was investigated for hot-wire GMA bead-on-plate and fillet joint welding. High-speed imaging and cross-sectional observations showed that a large volume of molten metal from the hot wire created a forward flow of molten metal in the molten pool, which prevented an undercut and obtained a sound bead shape. Second, hot-wire GMA laser hybrid welding was investigated for fillet joints with the aim of obtaining sufficient root penetration at high welding speed. A sound bead shape having sufficient penetration exceeding 5 mm and sufficient leg lengths exceeding 7 mm without defects was obtained at a high welding speed of 1.0 m/min.