Abstract: A method and an apparatus for joining two workpieces by means of a processing beam by forming a weld seam along a lap joint, wherein a gap formed at the lap joint between the two workpieces is filled during welding. The processing beam performs a spatial oscillatory movement parallel and/or perpendicular to the joint during welding. The oscillation parameters of said oscillation, the feed rate, the power of the processing beam and the angle of incidence of the processing beam onto the surfaces of the workpieces are adjusted dynamically during the welding process such that the upper sheet is fused in line with demand and the melt flows from the upper sheet down to the lower sheet thus closing the gap. The gap height is measured permanently during welding and the process parameters are adjusted such that a reliable closing of the gap is made possible.

Abstract: A welding method for joining workpieces (10) made of hot-crack-sensitive materials at a lap joint by means of a remote laser welding device. A stitched weld seam (11) with the equivalent strength of a continuous weld seam (11) is produced from a plurality of weld seam sections (13). The power input of the laser beam (21) changes periodically between a minimum and a maximum value while the laser spot (22) describes an anharmonically oscillating pendulum motion on the workpiece surface plane (18). The welding and the formation of the weld seam sections (13) take place in the phases of the power input with the maximum value. The anharmonically oscillating pendulum motion takes place with an oscillation frequency of 2 to 25 Hz and an amplitude in the range of 1 to 20 mm. The method is intended for welding of hot-crack-sensitive aluminum materials, e.g. for production of automobile bodies.