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  1. #1
    JunkyardJ's Avatar
    JunkyardJ is offline Titanium
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    Question Brazing paste, flux & metal mix?

    I like to watch a couple shows late at night before I go to bed, Factory Made, and How It's Made. I know the narrator is an idiot and gets his facts wrong a lot of the time. Anyways, it's just neat to watch how they make certain things.

    So, in a couple episodes, I've seen a brazing paste, that looks to be the flux and metal ready mixed. One was a silver solder type goop, and another was brass/bronze based. It seems to me that would be IDEAL to repair broken cast iron where the original parts fit together well. Just apply to the inside of the joint and press the parts together as they're heated. Anybody with any experience with this type of thing?

  2. #2
    adama is offline Diamond
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    Yep you pritty much got it. Some of them benifit from a slow warm up to dry the mosture out before the full on heat. If it boils to hard it tends to displace the solder. All the usual rules about cleanlyness still apply. Some parts benifit from clamping to maintain alignment others that will sit still can just be heated as is.

    The real advantage is when you have a kiln - oven avalible. If you can go for a inert atmosphere in it even better. Simply load up, programme the cycle and return when done.

    The only issue i have seen with this approach is when you have a close fitting joint that has to slide together, say like a tube into a socket. Its hard to get enough solder prescent to do the job. Flat objects were it can be coated - settle together as it melts are the best approach.

    Solders/ brazes are also avalible in foils but i have never messed with thoes.

  3. #3
    Norman Atkinson is offline Titanium
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    Default Brazing paste

    I think that you are probably refering to something called 'solder paint or paste' which is silver/silver solder in powder form mixed in acid based flux.

    If so, that has been around a long time and doses something like 'tinning' prior to putting on a silver solder using a borax type flux.

    If you are talking about brazing with flux filled rods, again, this is old hat.

    Again, MIG( Metallic Inert Gas) can use filled wire as opposed to plain coated wire with inert gas/ CO2 ?argon as a shield/fux.

    As to brazing up a cracked cast iron item with one of them, I'd simply forget about it and go back to using a conventional flux and filler rod.

  4. #4
    JunkyardJ's Avatar
    JunkyardJ is offline Titanium
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    Question Anybody else have any input?

    Not that I question either of these guys opinions, but I really was expecting more input.

    The goop I was referring to is literally a paste, as in gel type suspension of metal and flux. I think that stuff would be IDEAL for a lot of applications outside of a mass production environment. Just curious if anybody tinkered with it using a plain old oxy acetylene rig like I would.

  5. #5
    Mike C. is offline Diamond
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    I have mixed in brass filings from working a brazed part with granulated flux before. Works great. Really helps get the surface tinned. I was using it on cast iron.

  6. #6
    peterve's Avatar
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    I have soldered cast iron together with silver solder with great succes
    But however I could only got it done after grinding the surfaces real smooth on a surface grinder

    Peter from Holland

  7. #7
    Rodl is offline Aluminum
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    The guys building custom bicycles are using this and it is a metal/flux mix all in one. It is supposed to be something really nice to use. You can find out more by contacting Freddy Parr at Fred Parr Dot Com !

  8. #8
    Cyclotronguy is offline Hot Rolled
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    Default Paste

    I've had Handy and Harmon make up a black flux with BAg-7 powder in a 400 mesh for high vacuum joints. Many of those joints have been done in situ with a torch. Usual caveat....slightly reducing flame. Works great.

    Cyclotronguy

  9. #9
    digger doug is offline Titanium
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    Fusion Inc Home Page

    As Adama posted, it's used a lot in oven brazing.

    We do use it with hand torch brazing, as well as
    pre-cut strips (looks like shim stock, can cut
    with scissors)

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