Comparison of two different nozzles for laser beam welding of AA5083 aluminium alloy

AA5083 aluminium-magnesium alloy is increasingly used by shipbuilding industry due to its high strength to weight ratio. Laser welding is a crucial technology enabling reduction of thermal distortion of the weld assemblies and enhancing productivity, but its application to these alloys is far from being a reliable technology. In this work a comparative study has been carried out on the influence of two different shielding gas delivery systems on the autogenous laser welding process of AA5083. Bead-on-plate tests have been performed by using a 2.5 kW CO2 laser source and helium as shielding gas, supplied respectively by a coaxial conical nozzle and a two-pipe nozzle. The effects of the variation of the main process parameters, i.e., travel speed, beam focus position, gas flow rate and nozzle standoff distance on the bead profiles (width, penetration depth, melted area), were investigated. Useful information has been obtained on the role of the welding nozzle geometry on the laser-matter interaction. Several sets of process parameters able to produce acceptable welds were selected. Some preliminary results have been presented on the laser butt welding of AA5083 3-mm-thick plates. Weld results are very competitive if compared with the state-of-the-art.