TIG newby trying to join two thin pieces of aluminum

I've got some heatsinks that are .050" thick. The heatsink fins are about .200" long and .050 thick, but the flat oppsite sides are where I'm welding on.

I can lay down decent beads on a single piece. The arc is nice and stable, and as long as I don't dwell to long, I don't get too much sag or any burn through.

However, when I try to do a T joint with two of them, the arc tends to wander between the flat portions of the horizontal and vertical pieces. I can't seem to get the arc to focus on the joint.

The two pieces have been cleaned with a virgin stainless steel brush and wiped down with acetone. I've even tried it without the acetone with no real observable difference.

I'm running at about 80Hz, 30% DCEP, and 70A max current with a 3/32" pure tungsten electrode and a #5 cup.

Any advice would be appreciated.

Bob

Reply to
BobW
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The trick to starting the arc between 2 thin pieces of aluminum is to be pre-emptive with the filler rod. You need to place the end of your filler rod at the joint between the pieces. Bring up the amperage very slowly until the very end of the filler rod melts into a tiny ball. Keep raising the amperage until the ball melts off the end of the rod and sits in the joint. Now heat the ball directly until it flows out to both pieces. This trick allows the arc to focus on the ball, therefore it doesn't dance between the 2 pieces.

BTW Dump the pure tungstens. They are only useful as fishing weights. Get some 1% or 1.5% Lanthanated tungstens for AC and DC. For high amperage AC use Zirconiated tungstens.

best of luck.

Reply to
Ernie Leimkuhler

Ditto on what Ernie said, but I would add that you would probably find a smaller electrode (1/16") easier to control at that current and metal thickness. Make sure your filler rod isn't too big as well.

Pete

Reply to
Pete Snell

BobW wrote in sci.engr.joining.welding on Sun, 6 Feb 2011 20:48:02 -0800:

I second what others have said so far.

And it might help to have thinner filler wire. You can use mig wire off the spool if you need smaller than 1/16".

Reply to
dan

Ernie,

What you say makes perfect sense. I realize, now, that the arc is jumping to the closest surface that's available.

I have tried placing the (1/16") filler rod flat against the joint, and then apply the heat. The good news is that the arc finds the rod, but the bad news is that the rod gets easily vaporized. I'm trying to keep the initial current lower to avoid this, but it's difficult (for me) to get control of the situation. I'm going to try some thicker rod and see if it's easier to avoid the initial destruction.

I was able to do a lap joint on some .063 aluminum without any trouble, and didn't need to stick the rod in first. It looks pretty good with no burn through.

After some practice, I'm also able to lay down beads near the bottom of an empty soda can. With that, I definitely need to keep the filler rod in there soon so it takes some of the heat and avoids dissolving that thin .013" material.

I will get some lanthanated electrodes.

TIG welding aluminum is hard. I have a lot of respect for those who can do it well. Give me about ten years and I'll be there.

Thanks for your help.

Bob

Reply to
BobW

The bottom of the can is easy. I once took a red bull can, and sliced around the middle. Rotated the 2 halves 90 degrees and welded it back together.

Back then I was TIG welding a lot more often than now. I would have to work at it a bit to do it again.

Reply to
Ernie Leimkuhler

It might also help to make the tungsten less tapered. It seems wrong, but a blunter angle makes a narrower arc.

Dan

Reply to
dcaster

Show off :)

The only real sheet metal TIG work I've had to do was modifying a truck box for my truck. This was a 12ga steel box, 60" max span cut down and rewelded and it was rather a pain to hold it in alignment while hopping around on it welding an inch or two here and there to limit the heat input. It came out ok though after finish grinding and a touch of spotting compound, and it didn't need to be perfect anyway since I had the box coated inside and out with Line-X to match my truck bed. The end product came out very nice.

Reply to
Pete C.

Good grief, Ernie! You are to a TIG torch what Yoda is to a light saber.

The Force is strong with this one.

Bob

Reply to
BobW

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