Scientists at Australia’s CSIRO have developed a high speed welding technique called Keyhole Welding. It is suitable for joining corrosion resistant metals and offers an alternative to TIG welding which has a limited penetration.
Their new technique uses high welding currents and a novel torch design and utilises a standard GTAW power source capable of delivering 500-1000 amps. It forms a keyhole in the molten metal produced by the arc. It is this keyhole that anchors both of the faces of the metals to be joined, forming a stable joint. It is claimed to be capable of punching through 12mm plate with ease.
In the new process the arc gas passes cleanly through the metal, making it highly reproducible and robust.
Another advantage of Keyhole Welding is that the process can complete welds in a single pass, minimising the possibility of contamination and increasing productivity, especially when materials thicknesses exceed about 5mm.
The process is suitable for corrosion resistant material such as stainless steels and titanium alloy. Welding speeds are dependent in material thickness, but welding that used to take hours can now be completed in minutes. As an example, single pass welds on 12mm plate can be done at 300mm per minute, 8mm plate at 500mm per minute and 3mm plate at 1000mm per minute.
The newly developed process also permits automation of the welding process.