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  1. #1
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    Brazing practice








    It's been years since I brazed copper tube. I got out some stay-silv 56 and white paste flux to practice on a scrap piece. The silver-56 filler flowed all the way through the joint and can be found around the perimeter of the pipe in the joint.. The inside of the fitting is stained and has a bit of flux marking. Next try will with with a lot less flux and some inert gas slowing through, to protect the inside from oxidizing. I'd be interested to hear recommendations on brazing methods. I have an oxy/acet setup with various tips, 0, 1, 2 for instance. I had it set for sightly more fuel than would produce a neutral flame.

    Are the copper clad fittings on a compressor very fussy about flux and temperature? I read they can burn off the copper clad and then you have a mess. I guess being hooked to the pot, they can take a bit of heat.

    I Have silv45 and silv56 available. Stay-Brite too, but we won't talk about that.... these connections have high pressure and vibration.
    Last edited by Larry2; 26-11-2006 at 05:38 PM.



  2. #2
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    Re: Brazing practice

    I'm in two minds over using flux.

    Originally told to only add to male section so that excess is pushed out of the joint when assembled.

    Now instructions seem to be to only flux the brazing rod by warming it and then plunging it into the dry flux.

    Second method reduces chances of contaminating internals of pipework.

    Obviously yes, use inert, dry gas when brazing.

    Nice photos by the way.
    Brian - Newton Abbot, Devon, UK
    Retired March 2015

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    Re: Brazing practice

    Best way to check a joint it to cut though it length-ways with a hack-saw.

    If the pipe comes away at the shoulder then it's a duff. If both parts stay together then it's a good one..

    Well it was good untill you just cut it....LOL

    Chillin
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  4. #4
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    Re: Brazing practice

    I normally used flux on the male fitting only. The real trick is to get the two surfaces very clean before applying the flux to the male part.

    It looks like you got a very nice joint on the fitting.

    You are correct about the copper plated steel connections They are a bit tricky to work on as the metals heat at dissimilar rates.

  5. #5
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    Re: Brazing practice




    I did a few more practice connections, burning up some of my precious silv45 in the process. I cut a couple of them open lengthwise to check on the capillary action. This is water pipe, not refrigeration pipe I'm using just for practicing. (That is why it's a sharp 90*)

    I seem to get a tiny void at this inside corner a few times now. What am I doing wrong that causes this?

    With clad steel fittings, is there anything one does differently? I know steel is a poor conductor of heat until you pick up a piece you set down and forgot you heated up.

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    Re: Brazing practice

    Larry
    your main problem is that water pipe is not the same thickness or quality as refrigeration pipe and tends to have more impurities in it. I am slightly confused as to what sort of rod you are using, if you are using a silbraloy or silfos rod ie rothenberger S2 why are you using flux as it is self fluxing. Or are you using silver solder if so the joints you have done are pretty good.

    Ian

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    Re: Brazing practice

    Quote Originally Posted by Larry2 View Post

    With clad steel fittings, is there anything one does differently? I know steel is a poor conductor of heat until you pick up a piece you set down and forgot you heated up.
    when you say clad steel fittings, you mean the steel fittings with a nano thin covering of copper?

    if so, I always sandpaper away the thin copper coating and use 60% silver rods with flux to braze it.

    the copper will most likely burn away, unless you want to spend an hour brazing one joint... and who knows how good the copper plating sticks to the steel anyways? when you braze it, the silver runs between the two copper surfaces, no contact with the steel, so in theory... in theory with enough pressure the copper could peel of the steel and blow the pipe out in theory
    -Cheers-

    Tycho

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    Re: Brazing practice

    I am using Harris Safety Silv45 1/16" wire solder. It's 45% silver, 30% copper, 25% zinc. Solidus 1250, liquidus 1370. It has no phosphorus, so stay-silv flux is recommended. It is mil-spec stuff. I also have some 56. It was a bit more silver colored and is supposed to flow even more nicely. I didn't see much difference.

    The compressor fittings are copper clad over steel. I don't know how thick the copper is, but it doesn't nick readily. I think it's clad this way to facilitate soldering. I share your concern about copper plating because I've seen plating peel up when plating processes were poorly controlled.

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    Re: Brazing practice

    Larry, for me, your solderings are just perfect.

    The little pinhole you have coud be avoided if you heated it perhaps a little bit more but I think you don't have to practise any longer.
    Anyhow, your brazing is 100% gastight, that's for sure.
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

  10. #10
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    Re: Brazing practice

    For brazing copper to steel/copper plated steel i usually heat the copper to red hot a few cm from the joint and once its nice and hot move the flame and the red hot area to the joint. Heat your brazing rod a little with the flame and dip into flux powder (the heat should make it stick to the rod) Draw the rod across the joint area to deposit the flux on the pipe. If you're using an oxyacetylene set keep the flame moving as its hot enough to melt the copper off the steel in no time. Not such a problem if your using mapp or propane torch.
    Once the joint is hot enough apply the brazing rod, once you've got some braze on the joint its less likely the copper will burn off the steel as the braze in the joint passes the heat to the copper. When finshed clean all the flux off as its corrosive. Be careful not to breath in the fumes when brazing as i remember reading that they're poisonous (cadmium ?)
    If its a rota lock valve open it halfway before brazing or it may stick shut and not seal if you do get it open. wrap a wet rag around it also.
    Most important thing is to clean the pipe and fitting with some degreaser/ paper towel. You often get a wiff of oil blown out of the stub when you pull the plug out or open the valve.
    If the paint has burnt off the stub or the valve put some galv paint on it. Some small compressors and driers have copper stubs and you can use ordinary rods which are easier and more forgiving to poor cleaning. Pass some Ofn through as you braze.
    Aslo don't use ordinary rods on copper plated stubs/valves etc as they can form brittle joints prone to leaking.

    Cheers Jon

  11. #11
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    Re: Brazing practice

    Thanks everyone for the help and comments.

    Jon, your absolutely right about drifting through the nitrogen during the braze. I did some practice joints without because I didn't care if my sample corroded inside. When I quenched it in water to have a look, a thin piece of corroded copper rinsed off. Had this been in a refrigeration circuit, that could end up in some unhandy location, like the txv. I wonder if the folks who installed this system used nitrogen while brazing the line set. I kind of doubt it.

    I'll try another practice piece or two, starting the heat from the tubing end of things instead of starting at the fitting.

  12. #12
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    Re: Brazing practice

    Has anyone brazed a titanium tube to copper? Its for a saltwater chiller I'm designing. I need the titanium for its anti-corrosion properties.

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    Re: Brazing practice

    http://www.deutschetitan.de/eng/profi/kb24.html

    There's some interesting information there. I recommend you contact the folks at www.jwharris.com and inquire about their products. Stay-silv 45 or 56 may work well, but it's best to ask. Flux selection is also important. Your brazing material may not have the corrosion resistance you seek from the titanium. What about stainless steel?

  14. #14
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    Re: Brazing practice

    Quote Originally Posted by easttn View Post
    Has anyone brazed a titanium tube to copper? Its for a saltwater chiller I'm designing. I need the titanium for its anti-corrosion properties.
    Would you be able to use a mechanical joint?

    Might be the best option in this case.

    Chillin
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    and go get a cuppa

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