Aluminium welding by beam addition of cw. and repetitively Q-switched multi-kW Nd:YAG lasers

To ensure a stable process when welding Al, the power density must exceed a certain threshold value. An increase of power density can be achieved with Q-switched pulses. To simultaneously obtain both high average power and high welding speed, the beam of a cw. pumped, repetitively AO-Q-switched 1.7 kW Nd:YAG-laser at PRF 60 kHz was combined with the beam of a 2.0 kW cw. Nd:YAG-laser. The foci of the two lasers were coincident on the surface of the work piece. Positioning was accomplished by using two separate focusing optics. As the spot size on the work piece increases with the cosine of the tilt angle between the focusing optics, the relative movement of the work piece and optics was in the direction of the tilt angle. The beams from both lasers were delivered via O 600 mu m optical fibres.