6-kW Nd:YAG-laser system for welding applications

High average laser output power was realized by combining the beams of three Nd:YAG lasers of the 2 kW class, each being coupled into an individual 600 mu m fiber. The end faces are imaged onto a 1 mm fiber, which then transmits 6 kW cw power to the processing station. With this laser system, butt and edge joints with up to 5 mm thick sheets of AlMgSi1 and AlMgMn4,5 were performed. Velocities of about 3 m/min in combination with filling wire and Helium shieldings gas yielded satisfying results. The sheets of 1.5 mm thickness were best welded with 8m/min and a O 1 mm wire delivery speed of 5-7 m/min. One of the drawbacks of the system is the deterioration of beam quality due to the tilt angle between the incoming beams, so that a 1 mm fiber has to be used. With a modular oscillator-amplifier system with fiber link it should be possible to use fibers with smaller core diameter.