TWI Industrial Member Report Summary 238/1984
M G Murch
The potential for mechanised pulsed MIG welding of thin aluminium alloy sections for mass production applications has been investigated. Lap, edge and unsupported butt welds were fabricated in 1.6mm thick 6010 and 5182 alloy sheet with 5556A and 4043A filler wire, as appropriate, and under three pulsed MIG welding modes, sinusoidal, constant current square wave and controlled voltage operation. Optimised welding parameters were established for every joint type and filler wire combination and the processes were assessed to BS 4870: Part 2. The tolerance of optimised welding procedures to a 10% change in a major parameter and joint fitup variations was also investigated.
Both sinusoidal and constant current square wave pulsing were capable of producing the full range of lap welded joints. The edge joint in 6010 alloy/4043A filler wire was obtained only with the constant current square wave pulsed welding mode. Unbacked butt welds in 6010 alloy with 5556A and 4043A filler wire required the enhanced arc length stability found in controlled voltage pulsing to producing acceptable results.
Fitup variations with up to 0.75mm gaps between sheets in the lap and edge joint configuration were acceptable, but a joint gap in butt welds could not be tolerated with either sinusoidal or constant current pulsed operating modes. The tolerance to welding parameter variations was limited with only the lap joint producing a range of acceptable results.
In sinusoidal pulsing, arc starting difficulties gave rise to wire buckling and burnbacks at the low current levels necessary for the production of butt and edge welds.