Laser Arc Hybrid Welding of Thicker 6000-series Aluminium Alloy : Laser-MIG butt welding of 8 mm 6082-t6

Abstract: Laser arc hybrid welding presents many benefits but has many parameters that must be optimised for it to work. It becomes even more challenging when welding thicker aluminium with the process. Welding of thicker aluminium alloys involves a lot of different challenges, on itself. This thesis presents some theory about welding of aluminium alloys and theory about laser arc hybrid welding. Welding trials on 8mm thick 6082 aluminium alloys is performed. A few welding parameters are tested and evaluated. A few welding speeds are chosen, and the laser power is chosen to the lowest possible to still achieve full penetration. The highest welding speed of around 4m/min is achieved at the maximum laser power at hand (10kW). A few autogenous laser welds are also welds as reference. Welding trials with integrated backing strips are also tested. The welding trials results in two process area which gives low porosity welds. At welding speed of around 0,5m/min and lower welds with low porosity can be achieved. Welding speed of around 4m/min and above also gives low porosity welds. In the process area between 0,5m/min and 4m/min the welds have a lot of porosity. The reason for the porosity is probably keyhole instability. Non full penetrating welds shows a lot of porosity in the lower part of the weld, this becomes obvious when welding with backing strip. Most of the welds welded without backing material have sagging top and excessive penetration. Only welds welded at the highest welding speed gave welds within the quality levels of chosen standards.