Hybrid welding with controlled short arcs - A variation of the reduction of the energy-per-unit length

Laser beam welding is a fast, non-contact joining method. It is characterised by a high energy density which allows high process speed with, at the same time, low energy input into the joining zone. The weld seams which have been thus produced are very narrow and have a small heat affected zone. It is, however, not possible to exert metallurgical influence on the molten metal using the laser or to bridge gaps without weld sag or root collapse. There is the possibility to add cold wire where, however, comparatively expensive laser power for melting the wire must be used. Another approach is laser GMA hybrid welding with spray and/or pulsed arc. The energy-per-unit length is, however, strongly increased, thus problems caused by residual stresses and distortion in the component and also hot cracks in the weld may be developing. Conventional hybrid methods do, moreover, not permit the welding of plates with galvanised surfaces, since the GMA process shows instabilities caused by the explosive zinc burn-off. Due to this problem in laser beam GMA hybrid welding, the industry requires a joining method which combines the positive properties of laser beam GMA hybrid welding with a lower energy input. This method may be laser GMA hybrid welding with the addition of low-energy arc welding methods. The results of this project may, on the one hand, be beneficial for companies who apply laser GMA hybrid welding successfully already and who require a further minimisation of distortion. On the other hand, the process-oriented consequent further development of laser beam GMA hybrid welding allows the manufacturing of parts and components which have, so far, not been produced because of joining restrictions. It is, particularly with regard to the welding of coated materials, the distortion and the process stability, possible to generate advantages.