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Thread: Silicon Bronze Brazing

  1. #1
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    Silicon Bronze Brazing

    Hi all,

    I'm a novice welder trying to mig braze some copper sheet metal together for an art project. I'm using .023 silicon bronze wire on a Lincoln 140HD with Argon gas. The problem is that the braze doesn't stick to the copper and creates little globules that fall right off. I've tried varying power and speed and don't notice much difference in the outcome. Anybody have any ideas why this might be happening? Thank you!

  2. #2
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    Re: Silicon Bronze Brazing

    What has are you using?
    Last edited by tapwelder; 10-21-2021 at 07:15 PM.

  3. #3
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    Re: Silicon Bronze Brazing

    I'm using Argon

  4. #4
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    Re: Silicon Bronze Brazing


  5. #5
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    Re: Silicon Bronze Brazing

    Yes, 100%

  6. #6
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    Re: Silicon Bronze Brazing

    Is your copper clean? No coating? Actually copper sheet? Thickness?

  7. #7
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    Re: Silicon Bronze Brazing

    Yes, it's copper sheet and I've sanded the areas to be brazed. It's 24 gauge, fairly thin.

  8. #8
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    Re: Silicon Bronze Brazing

    Polarity? What wire was in your machine previously? Ground connection solid?

  9. #9
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    Re: Silicon Bronze Brazing

    Polarity is DCEP. I had stainless steel in there previously. As far as the ground connection, I clamped right onto the sheet so I think it was pretty solid.

  10. #10
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    Re: Silicon Bronze Brazing

    It seems like you are not getting enough heat for capillary suction. I have a spool of 030 silicon bronze wire.
    I haven't tried it yet But I'm sure it is recommended 130 to 140 amps that is probably more than your 140 can handle
    Last edited by Josey; 10-21-2021 at 09:39 PM.

  11. #11
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    Re: Silicon Bronze Brazing

    I was afraid it could be something like that.

  12. #12
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    Re: Silicon Bronze Brazing

    Try preheat.

  13. #13
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    Re: Silicon Bronze Brazing

    Quote Originally Posted by tapwelder View Post
    Try preheat.
    LOTS of preheat,, close to melting the copper type of preheat,, CRAZY hot copper.

    your problem is that copper can conduct away any heat that your welding machine tries to add.
    the copper has to be so hot, that when your machine adds heat, the copper has no where to put it, so, the filler metal "sticks" to the copper..
    In the case of brazing, it is much the same, the copper has to get so hot that the filler will "wet" to the copper,,
    that temperature is gonna be close to melting.

    OR,, you can go the other way,, get a machine that can output 300 amps, then not quite so much preheat will be needed,,,

  14. #14
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    Re: Silicon Bronze Brazing

    I suspect SweetMK nailed it, but just for grins, try putting some 20 Mule Team borax on your workpiece before trying to braze it. Probably won't work, but worth a try.

    Whenever I use SiB to braze, I use an O/A torch and borax flux, and it works fine, though I've never tried to braze copper...

  15. #15
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    Re: Silicon Bronze Brazing

    Thanks everyone, I will try those suggestions and see what happens.

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