ABICOR Innovation Award 2006 (1st Place)
Dr.-Ing. Sven-Frithjof Goecke (EWM HIGHTEC WELDING GmbH)
"EWM coldArc - energy-reduced short arc"
With the latest development of new materials, lightweight construction is undergoing rapid progress not only in the automotive sector. In future, further lightweight construction potential will only be able to be realized, however, where the jointing technology for thin high-strength and super high-strength steel plate and for material combinations such as steel with magnesium or aluminium can provide practical solutions. In these cases, the implementation of existing material-related and design possibilities is coming up against limiting factors in conventional jointing processes, particularly the productive metal shielding gas jointing technology.
The development of high-performance light arc processes in the 1990s and the boom of laser and laser-hybrid technology in the high-end capacity range was followed by an extension of the previously known MSG process limits to the "cold" end. Process approaches on the basis of short-circuit effected material transfer have proved to be showing the way.
With coldArc, an MSG process has been developed which generates a controlled melt volume through as little energy input as possible into the wire additive as well as into the component. For this purpose, a pulse-type melting process takes place in the light arc phase but without any free drip transfer. In the subsequent material transfer in the short-circuit phase, the energy input is adapted to the material in order to guarantee a controlled "soft" re-ignition. For this purpose, a drastic reduction of the power peak during cyclic light arc re-ignition is actively achieved, which makes a significant reduction of the heat input during this sensitive ignition phase possible.
The principle of the technology, implemented exclusively in the energy source, lies in the development of a particularly high-dynamic inverter circuit, whereas in a separate digital signal processor (DSP) high-speed digital process regulation monitors the pinching of the short-circuit separation in the µ-second range.
With an almost powerless material transfer, an MSG process can be used for the very first time to joint very thin metal sheets of less than 0.3 mm as well as use additive materials on a magnesium or even zinc basis (Ts around 400°C) for the "cold" jointing of mixed compounds of light alloys with steel. As an alternative to MIG soldering with a copper-based solder, the use of zinc-based electrode wire allows zinc-plated steel plate to be soldered using the same material, while the corrosion-protection zinc covering remains intact on both sides of the sheet metal.
Beyond use in all standard applications of short arc welding, further fields of application can be found in the combination of coldArc with laser and plasma technology for flux-free jointing where it is important to master the very thin line between as cold a jointing as possible while at the same time maintaining large component tolerance and high process stability.
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