Plasma augmented laser welding of 6 mm steel plate

A hybrid laser arc welding system incorporating a plasma arc in a triangulated configuration (plasma augmented laser welding – PALW) was used to produce bead on plate welds in 6 mm low carbon steel. Laser powers up to 5 kW and arc currents up to 150 A were investigated. Plasma augmented laser welding allowed an increase in full penetration welding speed of 100% or an increase in penetration of between 25 and 100%, compared with the laser alone. At speeds of 2 m min⁻¹ and above, PALW and laser alone were found to be equal with respect to fusion zone area per kW (mm2 kW⁻¹). Plasma augmented laser welding was equivalent in terms of welding energy utilisation (mm³ J⁻¹ of fusion zone) at 2 m min⁻¹ and superior above 2 m min−1. Full penetrating PALW allows significant energy losses via the keyhole root exit. Only when the keyhole root closes can the full benefits of the hybrid process be manifested in the workpiece.