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TIG welded aluminuzed exhaust and violent Popping/spattering occured what happened?

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  • TIG welded aluminuzed exhaust and violent Popping/spattering occured what happened?

    Yesterday a buddy brought over a new exhaust he bought from autozone for me to weld up. it consisted of a "Thrush welded" POS aluminized muffler and some 2" aluminized pipe. Everything welded nice as it should until i got to the muffler then i dont know what kept happening but it kept violently popping the weld pool out of the weld. At one point it popped up so bad that the weld went verticvally up and landed rigth in my hair giving me a nice bald spot to deal with. looking at the weld afterward i saw a major crater in the weld where the material had popped out. Logically to me it seemed like some sort of gasses were getting trapped behind the weld and expanding violently but im not understanding how when the pipe was open on one side and the muffler was open on the other. It was definely scarry and i'd like to figure out what happened to avoid it in the future.

    Machine was a sync 250
    2% thoriated
    er70s filler
    90 amps
    DCEN


    Anyone know what was happening. The only pics i have is when it was completed. None of the carnage.



    Flange came out pretty good
    Last edited by TTNickSoCal; 12-10-2012, 01:49 PM.

  • #2
    It happened because of the aluminized coating on the muffler. I dont know the specifics on the coating but it should be ground clean like you would do for welding galvanized. You are correct about the gases created by the coating building up in the puddle and eventually popping out.

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    • #3
      I thought it may have been an issue with the coating but i thought i grinded it all off. Maybe the inside of the pipe had it, which i didnt remove.

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      • #4
        The pipe may have been aluminized and the muffler zinc or something else coated.
        You gotta clean it for sure.
        CG

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        • #5
          Your first weld is obviously not aluminum, so if you are welding an aluminum exhaust to steel or s/s pipe, it is not going to work. Aluminum only welds to alum. Steel and s/s can be welded together. And all coatings should always be removed prior to welding.

          The way you can check materials is by grinding, aluminum makes no sparks but clogs up grinding/sanding wheels. S/S makes small grind spark trail. Steel makes a large grind trail. Zinc coating can have a trail that goes between steel and s/s.

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          • #6
            It was Aluminized Steel pipe. Pretty common on cheap exhaust piping. I hope i can tell the different between aluminium and steel at this point. hahaha

            http://en.wikipedia.org/wiki/Aluminized_steel

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            • #7
              The type of wheel you used for cleaning could have been the issue to. I find that when i use a regular grinding wheel to prep galvanized, the disc will load up with zinc and re deposit it on clean metal again. I use scotchbrite blending wheels on a velco backing wheel to clean coatings. I find that since they don't dig into the base metal, there is alot less problems with contamination. They come in different grades too, Like different grit flap discs do.

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