Effects of superposition of 532 nm and 1064 nm wavelengths in copper micro-welding by pulsed Nd:YAG laser

Unstable and low absorption of laser energy is experienced in copper welding at around 1000 nm wavelength. At 532 nm wavelength, there is stable and high laser absorption by copper. Past researches have shown that transitional processing condition between keyhole and heat conduction welding results in a stable micro-welding process characterized by good surface quality and deep penetration. In order to adapt laser welding to copper using pulsed Nd:YAG lasers, investigations of welding quality and efficiency were addressed. Processing was done under transitional processing condition between heat conduction and keyhole welding. Copper C1020 specimens were processed using superposed laser wavelengths of 1064 nm and 532 nm. Effects of irradiation delay and power density on the process were clarified by taking measurements of molten volumes, and by analyzing the weld beads. In addition, the dynamics of molten area and keyhole formation were investigated through three-dimensional FEM analysis. A stabilized laser absorption and increased molten volume was achieved by superposition using 532 nm laser of an appropriate high power density coupled with a short irradiation delay for the 1064 nm laser, which resulted in high-efficiency welding of copper.