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tig welding thin steel tubing

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  • tig welding thin steel tubing

    When you are tig welding thin guage steel tubing say from like .035-.065 are you supposed to completely penetrate through the tube...i.e. be able to see the underside of the weld when you look inside the tubing after your done?
    Last edited by torch; 01-14-2011, 09:04 PM.

  • #2
    You will see your heat affected zone when you look inside the tubing, but Im not sure what you mean by see the weld. If your going to butt joint the tubing together, and just tig fuse your tubing, your gonna get 100% penetration on your weld, and if your speed and heat is right, your weld on the inside of the tubing should look seamless.
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    • #3
      If you're making a tee- joint or a cluster of tubes, sometimes if you look inside the tube, you will see some burn throught. I know the mountain bike guys don't like to see any burn through at all. I also know however, that for AWS 17 (aerospace) certification they don't care of you have burn through-- as long as it's not too gross. ie. no huge grapes hanging down inside the tubing. The only thing they look for in the AWS 17 chromoly test is:

      full fusion with no inclusions of any type in a butt weld (checked via x-ray)

      at least 90% penetration with no inclusions on a fillet or cluster weld (also via x-ray)

      On the real light stuff it's hard to not get at least a few little bumps and t*ts on the inside of the tube
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      • #4
        Originally posted by torch View Post
        When you are tig welding thin guage steel tubing say from like .035-.065 are you supposed to completely penetrate through the tube...i.e. be able to see the underside of the weld when you look inside the tubing after your done?
        I tig weld mainly thin steel tube these days and all my butt welds are purged and 100% penetration. The welds are stronger, look nicer etc. Correctly done purge welds will look as good or better on the inside than the outside as the gas coverage is better.
        mike sr

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        • #5
          I tried to upload a pic from my camera, but my computer is not letting me..By seeing the underside of weld , I mean there is 100% penetration...it looks like a fusion weld without filler, but on the inside of the tube, in a complete circle..It is a bunch of .049" scrap round tube i cut up to practice on, Im trying T joints..I dont really have any bumps ,more like some low spots..This is happening on the piece of tube that did not get the notch cut in it, on the upright tube it is blistered mill scale and just some little tiny spots where the weld seeped in
          Last edited by torch; 01-15-2011, 04:12 PM.

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          • #6
            Originally posted by popspipes View Post
            I tig weld mainly thin steel tube these days and all my butt welds are purged and 100% penetration. The welds are stronger, look nicer etc. Correctly done purge welds will look as good or better on the inside than the outside as the gas coverage is better.
            Yeah I would definately do this, on a project, isnt there some kind of flux you can use too?

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            • #7
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              a picture of the inside and outside of a weld on carbon steel .0625 to .030, purged with 3 cfh, 5 cfh on the torch #4 cup .040 thoriated tungsten 100% argon.

              This is a small weldment approximately 3/4" ID and its kind of difficult to get the inside pic. but this will give you an idea of what it looks like.
              mike sr

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