Continuous Wave Laser Welding of Copper with Combined Beams at Wavelengths of 1030 nm and of 515 nm

The low absorptivity of similar to 1 mu m laser *beam sources in copper materials is a major challenge. Deep penetration welding at similar to 1 mu m is only possible with brilliant lasers providing high power and small focus diameters. The absorptivity increases with shorter wavelengths and higher temperature of the surface of the specimen. To exploit these facts, a 1 mu m and a frequency doubled thin-disk laser were combined. The precursory green laser beam is used to heat up the surface. Under these conditions the IR-beam interacts with the preheated material which leads to an enhanced absorptivity and a lower threshold for deep-penetration welding.