The Effects of Pulse Shaping Variation in Laser Spot-Welding of Aluminum

Aluminum alloys are important structural materials because of their high strength to weight ratio. Unfortunately, due to their high reflectivity and complexity in heat treatment, aluminum alloys are some of the hardest metals to be laser welded successfully and very high laser power is usually required. In this study, the feasibility of using a 220 W Nd:YAG laser for spot welding of aluminum is investigated and mostly focused on shaping of the laser pulse. All aspects of the laser pulse including initial coupling, weld fusion, and cooling will be discussed. Different pulse shaping methods like standard pulse shaping, ramp-down pulse shaping and ramp-down with rectangle initial coupling were used to investigate their effects on the weld characteristics. The results show that, with proper control of welding parameters, the success of aluminum welding can be achieved at considerably low laser power with minimal formation of typical welding defects (porosity, cracking etc.). The deepest penetration achieved was 834 μm with ramp-down pulse shaping. From quality point of view, ramp-down pulse shaping and ramp-down with longer initial coupling gave the best results.