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Thread: Brazing here?

  1. #1
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    Default Brazing here?

    Is this a good place to ask questions about brazing with oxy-acet?

    Jordan

  2. #2
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    Brazing is a form of welding, so what would you like to know???
    To grow old is mandatory, growing up is optional.

  3. #3
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    I thought it were more like soldering, as the base metal doesn't melt.

    Anyway, the question I have, as a full time amateur at this, is how to get a better result when butt brazing steel pipes?
    The pipes are to carry water under slight pressure - it's part of the cooling system in a bus.
    I can't reliably make it water proof. Under a simple test using tap water pressure, holes that are not obvious or even visible reveal their presence with tiny jets of water coming out of them. Remelting the braze doesn't seem to help.
    I'm using some brazing rods of unknown alloy, a light yellow colour. Also, tobin bronze just to try it because it's here. Flux is "copper & bronze" type.
    Any advice, folks?

    Jordan

  4. #4
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    Quote Originally Posted by nadroj View Post
    I thought it were more like soldering, as the base metal doesn't melt.

    Anyway, the question I have, as a full time amateur at this, is how to get a better result when butt brazing steel pipes?
    The pipes are to carry water under slight pressure - it's part of the cooling system in a bus.
    I can't reliably make it water proof. Under a simple test using tap water pressure, holes that are not obvious or even visible reveal their presence with tiny jets of water coming out of them. Remelting the braze doesn't seem to help.
    I'm using some brazing rods of unknown alloy, a light yellow colour. Also, tobin bronze just to try it because it's here. Flux is "copper & bronze" type.
    Any advice, folks?

    Jordan
    A light yellow colour, sounds like Silver Solder which requires a different flux, I think from memory is a Borasic Acid based paste.
    Unfortunately without knowing exactly what rods you're using, can make re soldering an issue. Silver solder should flow over the top sealing it.
    Personally, for plumbing on a cooling system I'd prefer to use Copper tube and Silver Solder the joints.
    Kryn
    To grow old is mandatory, growing up is optional.

  5. #5
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    Thanks Kryn,
    It's more yellow than silver solder.
    Copper tube would be good, but a lot of work has gone into bending steel tubing and will stay with that.
    Next thing to try is a different type of filler rod - but which one?

  6. #6
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    Default

    Pictures are worth a thousand words !

    Is it possible that you are getting the work piece too hot?

    holes that are not obvious or even visible reveal their presence with tiny jets of water coming out of them
    With brazing or soldering it is important to get the work to the required temperature for the filler to flow correctly, once you go above that temperature you can easily get to the point that the filler will start to bubble and spit causing pin holes in the finished joint. Oxy Acetylene will easily push above ideal temp's particularly with small parts.
    The brazed or soldered joint should have a smooth or glass surface finish across the joint.

  7. #7
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    Thanks Droog,
    That could be the problem, will try less heat.

  8. #8
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    When I go to braze, I put the tip of the rod into the flame to melt off a small piece, remove the rod and when the piece starts to flow, I know I'm at a correct temp. This may or not be the correct way but it works for me. Are you using galv pipe/tube as that can cause a problem also?
    Kryn
    To grow old is mandatory, growing up is optional.

  9. #9
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    It's not galvanised.

  10. #10
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    Are you dead set on using plain steel? sounds like recipe for disaster to me

  11. #11
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    Plain steel tube is commonly found in the cooling systems of engines and presents few issues provided cooling system corrosion inhibitor is used.
    Butt brazing steel tubing however could be an issue when vibration and flex in engine mounts is taken into account.
    Typically, brazed joints itilise some form of mechanical joint such as a sleeve joint or flared joint. While vee butt joints are used, they generally are found in sections of increased thickness.

  12. #12
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    I agree, butt joining isn't ideal.
    However, that's the way the owner has organised it.
    The joints have been initially tack welded, which would hopefully provide more strength, then brazed.

  13. #13
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    Many years ago I used this -

    Comweld Comcoat C – 2.4 / 3.2 mm – Cigweld

    Was good for butt joining RHS.

    There is also a similar product with a pink coating, that IIRC was good for building up worn shafts and may be an option, but you need to do some research on that, as I have forgotten.
    Nev.

  14. #14
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    Thanks Nev,
    The owner has bought some manganese bronze rods, and some flux paste.

  15. #15
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    Seriously ..... but brazing any form of water pipe is just not going to happen ...... serioulsy don't do it end story.

    You need to get some sort of sleeve or flange joint .... minimum

    cheers
    Any thing with sharp teeth eats meat.
    Most powertools have sharp teeth.
    People are made of meat.
    Abrasives can be just as dangerous as a blade.....and 10 times more painfull.

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