Fundamental study on welding phenomena in pulsed laser-gma hybrid welding

Abstract

Hybrid welding phenomena such as the interaction between the arc and laser plume, bead formation and metal transfer have been investigated. CW or power modulated CO2 laser is combined with pulsed GMA process. Pulsing frequency, arc current and arc voltage have been controlled in such a way that one droplet transfers per one pulse. The critical welding speed is significantly improved in the hybrid welding compared with the GMA welding due to formation of stable molten pool. The interaction between the arc and the laser plume is clearly observed during the base period of the arc. The arc is attracted by the laser plume due to high electrical conductivity of the plume. Spatter generation is influenced by the interaction, since the direction of the electromagnetic force changes. On the other hand, the arc sometimes continues to interact with the laser plume also during the peak period. This causes a reduction in the arc current due to large arc length, resulting in unstable metal transfer and spatter generation. Laser power modulation synchronized with the arc voltage is effective in preventing the unstable metal transfer.Hybrid welding phenomena such as the interaction between the arc and laser plume, bead formation and metal transfer have been investigated. CW or power modulated CO2 laser is combined with pulsed GMA process. Pulsing frequency, arc current and arc voltage have been controlled in such a way that one droplet transfers per one pulse. The critical welding speed is significantly improved in the hybrid welding compared with the GMA welding due to formation of stable molten pool. The interaction between the arc and the laser plume is clearly observed during the base period of the arc. The arc is attracted by the laser plume due to high electrical conductivity of the plume. Spatter generation is influenced by the interaction, since the direction of the electromagnetic force changes. On the other hand, the arc sometimes continues to interact with the laser plume also during the peak period. This causes a reduction in the arc current due to large arc length, resulting in unstable metal transfer and spatter generati...