Thin tubing TIG welding question


I am trying to welding a one inch long piece of 1" x .049" tubing to a

1" wide x .090" metal strap (all 4130). The tubing lays sideways on the strap so I have 2 wedge-shaped areas on each side of the tube that need to be filled. Problem is trying to get filler material into the narrow area where the tubing contacts the flat strap. I extend the .040 tungsten and am using .045 rod but in trying to get enough heat in there to melt the filler and get it to drip into the bottom of the wedge causes burn-through.

All I can think for doing is building up filler on the strap until it contacts the tubing but this leaves empty space at the bottom of each wedge where the tubing contact the strap. Any suggestions? Thanks

Rick Holland

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Why are you trying to use a 0.040" tungsten? Move up to a 1/16" tungsten, a and gas lens collet body. Use a #7 or #8 gas cup, and extend the tungsten 1/2" beyond the gas cup. Cut a short length or 1/16" filler and drop it down into the joint to fill the gap. Now weld over it.

Reply to
Ernie Leimkuhler

*Caution, newbie welder at keyboard*

Rick, when the burn through happens, how big of a hole does it make? If its fairly large, what may be happening is the inside of the tube is getting hot enough to react with the oxygen, and "whosh" a big burn thru hole.

I've had pretty good luck welding short (or thin) pieces of aluminum tube by strategically blocking up the tube with scrap material, (small Al plates or whatever), then purging the inside of the tub with Argon from the tig torch, and then quickly start welding on the outside of the tube.

In my case I was welding 5/8 solid aluminum hex bar stock, to 0.06" wall square tubing. I was having a lot of problem with burn thru on the tubing until I placed to flat plates on each end of the tube. Right before I started welding, I would move one plate, blow some argon down the tube to try and displace the oxygen, set the plate back in place and then quickly get to welding the bar stock in place. Either this worked, or my technique got better :).

Here's some pictures showing what I was trying to do, and the results:

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Take Care, James Lerch

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(My telescope construction, Testing, and Coating site)

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Reply to
James Lerch

I was trying to use lower amperages to try to prevent the burn-through problems (and the cavity I am trying to fill is so narrow) and figured I needed thinner tungsten. I will go back to the 1/16". I have been using a #5 gas lens collet body with about a 1/4" opening because the whole thing is small diameter and I can get it further into the narrow cavity but it sounds like I need to do the opposite, extend the tungsten further, use a large gas cup with a large opening and blast it with the argon.

Still have a lot to learn.

Thanks Ernie

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In my case its *Caution, newbie welder at welding torch*

The burn throughs happen half the time at the edge of the tube and half the time at the edge of the strap, so I think bad technique is the culpret here. I will take Ernies advice and practice on a dozen or so more pieces and see what happens.

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