Plasma arc keyhole welding is used successfully in industrial fabrication for welding high alloyed steels and titanium, and more recently structural steels. Due to a lack of reliability and knowledge, the use of plasma keyhole welding is uncommon in the Industrial welding of aluminium and its alloys. The high potential for high productivity and single pass welding of thick plates, gives the plasma keyhole process significant advantages over conventional welding methods such as TIG and MIG welding. The possibility and potential of applying VPPA (Variable Polarity Plasma Arc) welding to aluminium, especially to the alloys AlMg4.5Mn (AA 5083) and AlZn4.5Mgl (AA 7020), has been examined. It is shown that it is possible to achieve high quality welds free of defects, but the tolerance for variations in welding parameters, especially for the highest weld quality, is narrow.
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