Experimental investigation on arc characteristic and droplet transfer in CO2 laser–metal arc gas (MAG) hybrid welding

The present work reports results obtained using computer-based system techniques to investigate the metal transfer in laser–MAG hybrid welding. This arc characteristic information can be recorded by combining the sensing of the welding current and arc voltage with high speed imaging of the droplet transfer. An LD pumped green laser was used to overcome the strong interference from the welding arc. The arc energy determined mode of droplet transfer. When the arc energy is less than 4 kW, the transfer mode is short circuit transfer, or globular transfer or transfer mode between short circuit and globular. When the arc energy exceeds the 4.68 kW, the transfer mode is spray type. The laser energy has an important influence on the arc length, droplet size and the droplet velocity. When the arc energy is less than 4 kW, the attraction and compression of laser on arc play an important role, which caused the average arc length increases with increasing laser power. When the arc power is beyond 4.68 kW, the average arc length is decreasing with increasing laser power, which is attributed to expansion of the arc plasma, and enhancement of jet force of metal vapor on droplet. The droplet velocity decreases with increasing laser power, which is attributed to the attraction force of laser plasma to arc and the jet force of metal vapor produced by laser keyhole on droplet.