I have tried recently tried to weld aluminium with tig and I have a few questions.
First of all, I followed the advices that google found for me in this newsgroup by the letter: clean (acetone and wire brush), short arc, orbital motion to start the puddle, about 40 A per mm. I am using AC and Argon.
The first problem I had was that my welds were collapsing into huge holes after a half centimeter. I do not have a foot pedal on my machine, but after a short read from the machine handbook (which could be better written...), I discovered the use of that second button on my torch: it allows me to choose a second intensity. Suddenly I was able to weld.
Or am I? I still have doubts. At present, my welding goes like this: a) -start with I1 b) -when I fear that the material will collapse into a hole, click and reduce intensity to I2 c) -with I2, the aluminium oxydises again (the shiny part becomes much smaller) d) -either with I1 or I2, add some filler, which tends to sit there in a big blob e) -(now for the "I can weld" part): back to I1, heat the blob with the arc, clean the piece next to it... the blob gently flows to the piece as soon as the piece is shiny f) -go back to b)
I1= 50A and I2= 30A, the piece is 1.5mm thick, same as filler wire,1.6mm lanthanated tungsten. I know I should start with something thicker, but this is what I have at present (and about what I want to be able to weld in the end). Balance is 10% into cleaning (the piece seems hard to clean). Tungsten gets hot and forms a shiny blue ball (which is normal with more cleaning action, I suppose).
This technique actually gets the job done, in the sense that the two pieces have their edges melted and that there is melted filler all the way to connect them. Penetration is a bit light, unless I have to fill a hole, of course.
However, this technique produces flat "flow" welds and I wonder whether I should aim for the "stack of dimes" look (but how?). What do you think?
More specific questions:
-is it actually ok to add too much filler and let it flow, directing it with the arc?
-if not, how does one add filler to the puddle (instead of next to it)? When I bring the wire to the puddle, it starts to melt as soon as it comes into the arc cone (and that is before it comes to the puddle). If I move the arc away from the puddle (to be able to let the filler come nearer), the puddle oxydises as soon as the arc moves away... and of course the filler will not flow into an oxydised puddle (but it will flow when I bring the arc back and clean again, see e) above). When I say "move the arc away", I mean "move it somewhere else": the distance between the tungsten and the piece stays about the same. Maybe I should tap the wire very quickly?
-is it normal that aluminium that is cleaned by the arc oxydises again as soon as power is reduced even under the argon shield?