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Tig welding Bronze

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  • Tig welding Bronze

    Can bronze be tig welded/brazed? I know silicon bronze rod can be used with iron based metals but I had a local artist call me today and she has a small part that is cast from a silicon bronze material and has a crack. I do not have a torch set so I can not braze it, the only thing I have available right now is my tig welder.

    I am afraid that if I heat it the part is just going to melt away and I will have ruined a nice casting. I was thinking about trying to make an aluminum backer to support and draw heat out of the part.

    -Dan

  • #2
    I recently TIG welded a bronze statue from a university. It was commissioned by the university over 50 years ago was cast at the now defunct Roman Bronze Works.

    A new replacement (cast in China) was quoted at $250,000. But the original with its history, was priceless.

    This is one of those jobs where you've never encountered a situation like this and not much is documented about it, so you have to really be good at playing it by ear and have the macadamias to take it on.

    First of all, the OA process is not recommended when welding artistic castings or statuary bronze. You can TIG it with silicon bronze filler. You'll have to preheat to around 500 degrees and run a nice clean root bead. You'll need AC to drive out the junk that is going to be in the casting. 80/20 will be alright for an inverter. You'll need to very quickly peen the root bead after you weld it, while it's piping hot. Do not allow it to cool. Fill the bevel up in one more pass. Peen again and allow to cool slowly, pretty much the way you'd do for cast iron.

    The reason you can't treat these things like some other metallurgically sound casting is because these artistic castings are not controlled in their chemical makeup. To me, the word "composition" means what metal and what percentage is in a piece. To an artist, that word means some big idea of collecting their thoughts and putting them to some medium or some other bull**** like that. Anyway, this results in castings that contain a lot of garbage you don't want to weld, like lead, magnesium, and zinc. The AC will blow it right out of there. Oh, and expect to use a LOT of amps. I used about 250 amps on 1/8" beads, but that was with AC sine wave.

    Hope this helps a bit.

    Comment


    • #3
      Thanks,
      I did a little reading in the welding bible (the Lincoln Book) and it says it can be tig welded too, so I am going to give it a go, I am going to see if she has a piece of scrap to test on.

      -Dan

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      • #4
        A few years ago I repaired a statue with AC tig and silicon bronze wire. It was with a dynasty 200 but i dont remember the settings. I also tigged up some bronze slides that I mis cut the grease passages in, the material was 1" thick and my cuts were only about 1/8 deep but I had to have the machine cranked all the way up and the pedal floored to get the puddle going but then it filled in real quick. Good Luck

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        • #5
          Well, I took the job on and had the artist bring some scrap pieces. It turned out to weld much easier then I thought it would and with a lot less heat then I thought it would need. I did take the advice given here and ran it on AC to take adavantage of the cleaning action, set it at 80% heat (20% cleaning) 120hz and had at it. I will try and remember to post some pictures tonight.

          -Dan

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          • #6
            That makes a big difference. I tried it DC like the books told me for industrial bronzes, but the crud got deep in a fast hurry and I found myself jamming the rod under the crud when I had the idea of using AC. Cleared that right up.

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