Once the aluminum has soaked up all the heat it can..

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Wondering if anyone has some tips on tigging aluminum, RE once the metal has reached that point where it's not soaking up any more heat and you have to start backing your current off.I'm used to reading O/A puddles, but by the time I pick up on what's going on toward the end of an alum stringer, I'm too late and I have to back the pedal off and start moving FAST. Obviously, even then, the last 1/1/2 inches of the bead does not match the rest.I guess what I'm asking is a puddle reading question more than anything, especially since at this point we're operating on settings that we're not really allowed to change. (School)Thermal arc 185135 amps35 wave balance (that's 65 for all you red and bluers)3/32 2% TH rod5052 alum, 16 GA equivalent (I know there's a difference, but it's damn close, can't remember the three digit callout)5356 wire2 inch by 6 inch blanks stamped out on a stomp shearAny help's appreciated, and I'm taking a camera with me from now on, so I'll throw a few pics up midweek in case it helps.If you fight long enough, you will win. The problem is it costs too damned much.- Lee Cheng
Reply:Originally Posted by bellflowerWondering if anyone has some tips on tigging aluminum, RE once the metal has reached that point where it's not soaking up any more heat and you have to start backing your current off.I'm used to reading O/A puddles, but by the time I pick up on what's going on toward the end of an alum stringer, I'm too late and I have to back the pedal off and start moving FAST. Obviously, even then, the last 1/1/2 inches of the bead does not match the rest.I guess what I'm asking is a puddle reading question more than anything, especially since at this point we're operating on settings that we're not really allowed to change. (School)Thermal arc 185135 amps35 wave balance (that's 65 for all you red and bluers)3/32 2% TH rod5052 alum, 16 GA equivalent (I know there's a difference, but it's damn close, can't remember the three digit callout)5356 wire2 inch by 6 inch blanks stamped out on a stomp shearAny help's appreciated, and I'm taking a camera with me from now on, so I'll throw a few pics up midweek in case it helps.
Reply:My simple answer..... is complicated!First; if you change torch angle and the distance from the work piece, the arc will change a lot and this is more pronounced than with steel, due to the lower melt point.Closer to the work means a smaller, more focused arc. It also means better control of the actual heat, and lessens the blob effect.Second; learn to modulate the pedal more through the entire weld. You can get to a point where you can run with the pedal WFO on decently thick material, or start full pedal and then quickly pull back to half pedal, 2/3 pedal, etc. and flow right along steadily. Or, you can start hot, and work the pedal more in tune with your dips. For thin material this tends to be a safer route to go; it is the more common way to deal with the end of almost all aluminum welds that end not landing on another piece or landing back on a weld like with welding a tube or pipe.Most times a puddle fails, it is going to go from a silver puddle, which is easy to read, to a graying silver. This means the puddle is oxidizing. It's a sign that it is oxidizing from the BOTTOM of the weld, and coming up and thru. It also can mean the arc is pulled away too far, and the puddle and pool is getting much larger than you anticipate. Then, the material as a whole reaches 1100 degrees, and......If you see the puddle getting larger, the first impulse is to pull the torch away to reduce heat a little. It kinda works on steel, but on aluminum it makes a mess. The shielding gas falls short, and the heat spreads more and the puddle fails. What to do: keep the torch close to the work piece, and back the pedal off, and dab filler in- all in one fluid motion. The filler will help draw a little heat, and solid up the puddle. The tip held in close keeps the actual arc small, which is what you NEED. And pedaling back is to actually reduce the actual heat applied.It is slightly counter-intuitive, especially for those who have done a lot of oxy-acetylene work.And then, after so much work...... you have it in your hand, and you look over to your side...... and the runner has run off. Leaving you holding the prize, wondering when the runner will return.
Reply:watch the puddle a little more closely, when you see the puddle start to grow larger than when you started, start backing down the heat, even pulse the peddle if you have to, it all helps, just try to not lose the puddle.