At the risk of causing confusion i'm gonna contradict pretty much everything, sorry.
7 litres/min is more than enough, the black stuff looks to be a combination of two things to me... the larger/sooty patches are weld smut, basically the result of trying to melt the filler wire with the arc (or trying to add wire before there's enough of a weldpool to accept it), touching the weldpool with the tungsten or the tungsten with filler. Any of those can vaporise some ally leaving blackish soot behind. The smaller/peppery spots in the weld beads... very little in the way of an etched zone (the white 'cleaning' bands) going on which can result in a weldpool with 'bits' in it. Biasing the AC balance a bit further towards EP (electrode +ve, more cleaning) should get rid of a chunk of them at least. The third pic has some autogenous (without filler) beads with a larger etched zone around them and no sign of black bits or weld smut...
The miller TIG calculator doesn't make much sense as while it's sometimes in the ballpark it's often miles out. The charts in this forums tutorials are closer to the mark for carbon/stainless and the best rule of thumb for a starting point on ally is 1A per 0.001" / 40A per mm although the thermal conductivity of ally messes with things some i.e. small parts/offcuts quickly get heat soaked
Obviously things like amperage charts for things like tungsten size are kinda useful when starting out but i wouldn't pay too much attention to them as the numbers Weldequip quotes don't agree with the numbers in the TIG FAQ which in turn won't agree with pretty much any other source
At the risk of causing confusion i'm gonna contradict pretty much everything, sorry.
7 litres/min is more than enough, the black stuff looks to be a combination of two things to me... the larger/sooty patches are weld smut, basically the result of trying to melt the filler wire with the arc (or trying to add wire before there's enough of a weldpool to accept it), touching the weldpool with the tungsten or the tungsten with filler. Any of those can vaporise some ally leaving blackish soot behind. The smaller/peppery spots in the weld beads... very little in the way of an etched zone (the white 'cleaning' bands) going on which can result in a weldpool with 'bits' in it. Biasing the AC balance a bit further towards EP (electrode +ve, more cleaning) should get rid of a chunk of them at least. The third pic has some autogenous (without filler) beads with a larger etched zone around them and no sign of black bits or weld smut...
The miller TIG calculator doesn't make much sense as while it's sometimes in the ballpark it's often miles out. The charts in this forums tutorials are closer to the mark for carbon/stainless and the best rule of thumb for a starting point on ally is 1A per 0.001" / 40A per mm although the thermal conductivity of ally messes with things some i.e. small parts/offcuts quickly get heat soaked
Obviously things like amperage charts for things like tungsten size are kinda useful when starting out but i wouldn't pay too much attention to them as the numbers Weldequip quotes don't agree with the numbers in the TIG FAQ which in turn won't agree with pretty much any other source
not really sure what to set the machine at there are to many button and knobs lol this is what i have gotquote]
I found breaking each function down to AC or DC use helped when trying to get used to all the knobs & knockers on my similar Tig machine.