ABICOR Innovation Award 2006 (2nd Place)
Dipl.-Ing. Frank Höcker (ISF Aachen)
Dr.-Ing. Konrad Willms (ISF Aachen)
MSG welding of aluminium using thin welding wires
In industrial practice, mainly welding wires with a diameter of 1.0 mm to 1.6 mm are used for the MSG welding of aluminium, since additive materials with smaller wire diameters can lead to problems with wire feed due to their tendency to buckle. The development of this new MSG process now makes it possible to use smaller wire cross-sections during aluminium welding.
This is achieved by an integrated forming process directly before the welding torch, during which the cross-section of an easily feedable 1 mm standard wire is reduced by up to 40%. The re-formed electrode cross-section has a rectangular shape. This reduction in cross-section and the reduced linear energy caused by this extends the area of application of MSG welding of aluminium to thinner sheet metals which could not previously be welded using this method.
This forming process is achieved using a jig similar to wire feed drive. The first pair of rollers is responsible for the largest share of cross-section reduction. The second pair of rollers mainly takes over the fail-safe feeding of the re-formed wire. The welding results achieved document the good process stability in the thin sheet metal range up to 0.6 mm. In addition, the spray arc process has been able to be extended to thinner metal sheets up to 1 mm.
A further unsolved problem is the use of light arc sensors for aluminium welding, since the electrical resistance of aluminium is approx. 10 times lower than that of steel. Electrical resistance depends on the cross-section, however. For this reason, re-formed wire results in an increase in the sensor useful signal in comparison with the initial wire.
With the reduced cross-section, a sensor useful signal of approx. 1.8 A/mm free wire length was achieved for the use of a light arc sensor system for spray arc and of 0.6 A/mm free wire length for the pulse light arc. The sensor useful signal achieved is not comparable with the signal for steel, but it does represent a significant improvement with regard to the use of a light arc sensor system for aluminium welding, particularly with the spray arc.
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