HYBRID WELDING WITH CONTROLLED SHORT ARCS - A VARIATION OF THE REDUCTION OF THE ENERGY-PER-UNIT LENGTH

摘要

Laser beam welding is a fast, non-contact joiningrnmethod. It is characterised by a high energy densityrnwhich allows high process speed with, at the samerntime, low energy input into the joining zone. The weldrnseams which have been thus produced are very narrowrnand have a small heat affected zone. It is, however, notrnpossible to exert metallurgical influence on the moltenrnmetal using the laser or to bridge gaps without weldrnsag or root collapse. There is the possibility to add coldrnwire where, however, comparatively expensive laserrnpower for melting the wire must be used. Another approachrnis laser GMA hybrid welding with spray and/orrnpulsed arc. The energy-per-unit length is, however,rnstrongly increased, thus problems caused by residualrnstresses and distortion in the component and also hotrncracks in the weld may be developing. Conventionalrnhybrid methods do, moreover, not permit the weldingrnof plates with galvanised surfaces, since the GMArnprocess shows instabilities caused by the explosivernzinc burn-off. Due to this problem in laser beam GMArnhybrid welding, the industry requires a joining methodrnwhich combines the positive properties of laser beamrnGMA hybrid welding with a lower energy input. Thisrnmethod may be laser GMA hybrid welding with thernaddition of low-energy arc welding methods. The resultsrnof this project may, on the one hand, be beneficialrnfor companies who apply laser GMA hybrid weldingrnsuccessfully already and who require a further minimisationrnof distortion. On the other hand, the processorientedrnconsequent further development of laser beamrnGMA hybrid welding allows the manufacturing ofrnparts and components which have, so far, not beenrnproduced because of joining restrictions. It is, particularlyrnwith regard to the welding of coated materials,rnthe distortion and the process stability, possible to generaternadvantages.