Brazing Rod Crisis

 
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Old 06-24-2012, 09:12 AM   #1
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Brazing Rod Crisis


You guys should have seen it. Last night at about 9pm I brazed the worst joint of my life. Now...that is saying something...considering I've been doing this about thirteen years, lol. I never even botched a joint that bad in tech school!

I want to blame it on the fact that (for the first time in my life) I am using 5% silver rod. I guess I've been so set in my ways with 15% all these years. Idk, but this "incident" (for lack of a better term) is going to cost me about a half days work.

Anyway, I could really use your input on things...so please feel free to answer the following questions.

FOR JOINING COPPER-TO-COPPER, in diameters up to 1":

Silver Content: 5%, 6%, 15%, other? (and why)

Brand: Stay-Silv, DynaFlow, Forney, Harris, other? (and why)

Flux: yes, no, maybe, some times, powder, paste, pros, cons, experiences? (and why)

Fuel: Oxy- or Air-Acet? (and why, keep in mind, this is copper-to-copper up to 1" diameter)

Torch Manuf: Harris, UniWeld, Victor, other? (and why)

Tip Style/Number?

I am in need of a serious refresher after last night's incident and am seeking any advice on the matter of brazing.

Thanks all.

Ivan


Last edited by VersaTek; 06-24-2012 at 09:36 AM. Reason: post went all catawompous and showed html code in a jumbled mess
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Old 06-24-2012, 08:59 PM   #2
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Re: Brazing Rod Crisis


15%, because it flows better.
What ever brand the supply house carries, as long as it 15%.
No flux.
Air acetylene.
Uniweld.
A14.
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Old 06-24-2012, 10:24 PM   #3
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Re: Brazing Rod Crisis


Quote:
Originally Posted by beenthere View Post
15%, because it flows better.
What ever brand the supply house carries, as long as it 15%.
No flux.
Air acetylene.
Uniweld.
A14.
Hey, thanks for the reply.

You ever have a joint go horribly wrong even though you "think" you did everything right?

This was a textbook joint.

3/4" copper to 3/4" copper with a slip coupling.

I cleaned all the surfaces (or so I thought) meticulously.

Removed the schrader core and applied a heat sink to the suction line service valve.

Preheated the area evenly.

It just would NOT FLOW.

As a stop-gap measure, I applied some stay-silv flux to the joint, thinking it would clean any residues. Fairly certain that made matters worse.

When a joint goes wrong like that, I just wish I knew the reason, so I won't repeat it in the future.

I don't know if it was the proximity of the heat sink (probably six inches down the line, doubt it), or some sort of oily residue that just wasn't coming off the fitting with sanding, or even worse - a problem with my technique.

This is an old condensing unit that had the quick-connect fittings, so there is technically no "service valve". Idk how those things connect, but I know I'm going to have to cut it out and install a new length of 3/4" tubing into the condensing unit itself and completely remove that for fear of being too close with the heat if I cut off the bad braze joint.

Blows.
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Old 06-24-2012, 11:06 PM   #4
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Re: Brazing Rod Crisis


basically, only if my B tank is low on gas. Then its hard to get the fitting hot enough.
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Old 06-25-2012, 08:08 PM   #5
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Re: Brazing Rod Crisis


I think this was a classic case of overheating the fitting because I had the wrong torch tip and also the fact that 5% brazing rod blows donkey balls.

I threw a couple of larger torch tips in my bag and got a killer deal on some Lenox 15% rod.

I figure by the time I had the fitting hot enough, it was heavily oxidized.
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Old 06-26-2012, 05:32 AM   #6
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Re: Brazing Rod Crisis


Small tips can be a draw back on large fittings.
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Old 06-26-2012, 06:43 AM   #7
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Re: Brazing Rod Crisis


Quote:
Originally Posted by beenthere View Post
Small tips can be a draw back on large fittings.
Indeed.

Since this happened, I'm considering switching over to oxy-acetylene on my personal van. I've been reading on it. I've used oxy-acet quite a bit too. Honestly, I've never really had a preference. It just depends on what my particular employer provides. In my personal time van, always used an air-acetylene torch.

That may be changing though.

I've been reading on carburizing vs. oxidizing flame. It's my understanding that if you run your oxy-acet a little oxygen deprived (or carburizing) that it will prevent oxide build up by robbing oxygen from the surrounding area.

This alone seems like a good reason to try it. Although in my reading I found a page that says to use a neutral flame for copper-to-copper.

Idk, I'll give it another shot and see what happens.
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Old 06-26-2012, 06:49 AM   #8
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Re: Brazing Rod Crisis


If your flowing nitrogen while brazing. Then a slightly carbonizing or oxidating flame make no difference on the inside of the fitting.
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Old 06-26-2012, 07:57 AM   #9
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Re: Brazing Rod Crisis


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Originally Posted by beenthere View Post
If your flowing nitrogen while brazing. Then a slightly carbonizing or oxidating flame make no difference on the inside of the fitting.
I do flow nitrogen. It's the outside of the fitting that concerns me. Not getting a good bond because of oxide.
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Old 06-26-2012, 04:22 PM   #10
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Re: Brazing Rod Crisis


Quote:
Originally Posted by VersaTek View Post
I do flow nitrogen. It's the outside of the fitting that concerns me. Not getting a good bond because of oxide.
Getting the joint hot fast is probably the best way to avoid that as far as brazing is concerned.

But give it a try, and see if you thought works better for you.
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Old 06-26-2012, 06:10 PM   #11
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Re: Brazing Rod Crisis


I'm going back Saturday...

This time with a larger torch tip and 15% rod.

I will report back.

Words can not express just how messed up this fitting was.

I should have saved it and taken pictures, but I was at the point of blind rage, so tossed it. Literally.
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Old 06-26-2012, 06:15 PM   #12
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Re: Brazing Rod Crisis


I done a few that were just hard to get to. Where I used the old saying. if you can't make it look nice, at least make it leak proof.
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