Trouble soldering SS to copper

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PeatyKeats
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Trouble soldering SS to copper

Post by PeatyKeats »

I know this is a topic that has been discussed profusely.

I’ve read the “How to solder SS to copper” thread from many years ago, I’ve seen tutorials, and I’ve read through other threads on this topic. I bought Stay-brite liquid flux along w/ silver solder, have a MAP torch, and followed the basic steps of soldering SS to copper.

I am trying to solder two 2” SS ferrules & one 1/2” SS ferrule to a copper tee. I followed the suggestion if tinning the silver solder in the joint. I had to use a shim in w each ferrule.
I managed to solder them, but when I checked to see if there were any leaks, both 2” ferrules leaked water. I tried touching them up, but couldn’t get it sealed.

My question is with respect to the gauge of the silver solder. Would it be best to purchase a silver solder that was a thicker gauge?
The solder that came with the liquid flux is very thin. I wonder if that may be part of the reason why it’s not sealing properly.

Thank you for any responses or suggestions.
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Re: Trouble soldering SS to copper

Post by Saltbush Bill »

Ive found the higher the silver content of the rod the easier it is to use......high silver content rods aint cheap though.
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Re: Trouble soldering SS to copper

Post by AlWorms »

Thicker gauge doesn't help - you just end up putting more on faster.

Stay-brite 8 silver solder has a temperature differential between it's liquid and solid states, that means if you get good at playing the torch of the work, you can stop it getting too "runny". The difference between solidus and liquidus is about 100F.

I find it MUCH easier than the standard Stay-brite, which has THE SAME liquidus and Solidus temp - it's either solid or runny, not anything in between.

As Saltbush Bill says - it's the higher silver content makes it easier.

Anything else with similar characteristics probably makes it easier, or make tighter fitting parts first - that helps a LOT, but is sometimes easier said than done!
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Re: Trouble soldering SS to copper

Post by Sporacle »

I also find I put the solder on the joint in the horizontal position and make sure I get a good cover on the stainless (I rotate as I go and do a bit at a time) once I have a good coverage on the stainless I let it cool and clean it really well being careful not to separate the joint, I re flux it and place the joint vertically with the ferrule at the top and reapply the heat and run the solder down into the joint and add solder as I need, take your time and it'll go eventually, good luck
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Re: Trouble soldering SS to copper

Post by PeatyKeats »

Thank you for the responses so far.

Sporacle wrote: Wed Sep 15, 2021 2:48 pm I also find I put the solder on the joint in the horizontal position and make sure I get a good cover on the stainless (I rotate as I go and do a bit at a time) once I have a good coverage on the stainless I let it cool and clean it really well being careful not to separate the joint, I re flux it and place the joint vertically with the ferrule at the top and reapply the heat and run the solder down into the joint and add solder as I need, take your time and it'll go eventually, good luck
Are you worried that the fitting might come loose with the heat in the horizontal position?
Nevertheless, I’ll give that a try.

Using liquid flux, is anyone truly worried about heating it up too much?
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Re: Trouble soldering SS to copper

Post by acfixer69 »

As with any flux heat can be a problem. What did you use to shim the fit and how clean were they. A pic would make it a lot easier to maybe spot a problem.
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Re: Trouble soldering SS to copper

Post by Sporacle »

Not to worried about it coming loose, we are lucky here that generally our ferrules need to go into a socket then pipe on stuff up to 2 inch I've found, I tend to set everything out and make sure everything is in position and won't move to much when I rotate them. I have found that set out, prep and patience are key to fitting ferrules, good luck
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Re: Trouble soldering SS to copper

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acfixer69 wrote: Wed Sep 15, 2021 3:21 pm As with any flux heat can be a problem. What did you use to shim the fit and how clean were they. A pic would make it a lot easier to maybe spot a problem.
I cut a 1” length if 2” copper pipe to use as a shim.
Sorry, but I don’t have a pic at the moment.
I would like to believe they were TOTALLY clean, as I’m all about preparation. Every video, or article, or post I've read talks about preparation being 90% of the job.

I’m wondering if the shim I made was not long enough.

The other possibility is that I didn’t flux enough with liquid flux.
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Re: Trouble soldering SS to copper

Post by acfixer69 »

The shim doesn't need to be long. It is only to bridge the gap. Keep the flux handy and the heat low and slow. Best I can mention with info given. Good news is all you have written sounds right.
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Re: Trouble soldering SS to copper

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acfixer69 wrote: Wed Sep 15, 2021 4:45 pm The shim doesn't need to be long. It is only to bridge the gap. Keep the flux handy and the heat low and slow. Best I can mention with info given. Good news is all you have written sounds right.

Thanks. Perhaps I heated too fast. I should pull back the heat from the pipe.

My other thought was, should I double tin the joint?
A circle of silver solder in between the SS & the copper tee (where they meet), and a circle of solder where the shim and copper tee meet inside.
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Re: Trouble soldering SS to copper

Post by acfixer69 »

Tinning isn't needed. But won't hurt either. The loose fit and shim is what I would suspect the problem. Last request for a pic.
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Re: Trouble soldering SS to copper

Post by rolling »

Gasflux. With stainless you need to braze, not solder. Higher heat. Use 56% silver and Gasflux U. It's a good place to start, steep learning curve.
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Re: Trouble soldering SS to copper

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acfixer69 wrote: Wed Sep 15, 2021 5:32 pm Tinning isn't needed. But won't hurt either. The loose fit and shim is what I would suspect the problem. Last request for a pic.
I’d post a pic, but I already took it apart. I’m going to clean it and try to redo it tomorrow.
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Re: Trouble soldering SS to copper

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PeatyKeats wrote: Wed Sep 15, 2021 1:30 pm
I am trying to solder two 2” SS ferrules & one 1/2” SS ferrule to a copper tee. I followed the suggestion if tinning the silver solder in the joint. I had to use a shim in w each ferrule.
I managed to solder them, but when I checked to see if there were any leaks, both 2” ferrules leaked water. I tried touching them up, but couldn’t get it sealed.
I also use Sta-brite 8 and liquid flux and it helps that ss be properly 'textured' by sanding (I use a bench grinder) for the solder to adhere. Also, I 'shim' my ferrules to fit copper fittings with 2" pipe. This ensures an ideal gap for soldering. When properly preparing both surfaces I haven't found the need to (pre) tin.
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rolling wrote: Wed Sep 15, 2021 5:54 pm Gasflux. With stainless you need to braze, not solder. Higher heat. Use 56% silver and Gasflux U. It's a good place to start, steep learning curve.
100% not needed. 56% silver solder is prohibitively expensive and overkill for the joint strength needed in this application.
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Re: Trouble soldering SS to copper

Post by PeatyKeats »

Twisted Brick wrote: Wed Sep 15, 2021 6:11 pm
PeatyKeats wrote: Wed Sep 15, 2021 1:30 pm
I am trying to solder two 2” SS ferrules & one 1/2” SS ferrule to a copper tee. I followed the suggestion if tinning the silver solder in the joint. I had to use a shim in w each ferrule.
I managed to solder them, but when I checked to see if there were any leaks, both 2” ferrules leaked water. I tried touching them up, but couldn’t get it sealed.
I also use Sta-brite 8 and liquid flux and it helps that ss be properly 'textured' by sanding (I use a bench grinder) for the solder to adhere. Also, I 'shim' my ferrules to fit copper fittings with 2" pipe. This ensures an ideal gap for soldering. When properly preparing both surfaces I haven't found the need to (pre) tin.
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IMG_1788 copy.jpg
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IMG_1871 copy.jpg
Thanks for the response. I’m trying to figure out where I went wrong, and perhaps I just over thought the process. All my copper joints have worked, including the copper ferrule I soldered today to my 2” copper riser.
Maybe it’d be best to start again simple, using the liquid flux and silver solder.

So, to be on the safe side, you simply made a copper shim that fit flush with the SS ferrule, and used silver solder on the joint without tinning?
I assume you fluxed both side of the shim and the other necessary surfaces…
Thanks.
Last edited by PeatyKeats on Wed Sep 15, 2021 6:16 pm, edited 1 time in total.
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acfixer69
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Re: Trouble soldering SS to copper

Post by acfixer69 »

rolling wrote: Wed Sep 15, 2021 5:54 pm Gasflux. With stainless you need to braze, not solder. Higher heat. Use 56% silver and Gasflux U. It's a good place to start, steep learning curve.
Bullshit NO NEED but is a way. Stop this needless nonsense.
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Re: Trouble soldering SS to copper

Post by Twisted Brick »

PeatyKeats wrote: Wed Sep 15, 2021 6:14 pm
So, to be on the safe side, you simply made a copper shim that fit flush with the SS ferrule, and used silver solder on the joint without tinning?
I assume you fluxed both side of the shim and the other necessary surfaces…
Thanks.
Yes, but I work mostly with Type L pipe which requires a slight reduction in ID for the ferrule to fit properly. I use a drill-mounted tungsten carbide cutting burr on the end of 2" pipe before cutting the shim off. A 5/8" shim fits the ferrule barrels nicely. After sanding my ferrule the reduced shims should slide onto it with very slight resistance. This encourages a complete 360* filling of solder. If you heat around the shim from the top down and feed the solder from the bottom, the solder will draw upwards and ideally give you a complete ring.

The shimmed ferrule will now slide into your fitting like a piece of pipe. I stand my pipe vertically onto the ferrule and like the shim, heat from the top down, about 1/2" above where the shim/ferrule terminates inside the pipe. Yes, all surfaces should be sanded and cleaned (I use alcohol) and fluxed (both mating surfaces). Just before applying solder I re-flux the joint, effectively removing any burnt flux. With the Harris silver solder this method has proved very solid with no need for tinning.
IMG_1769 copy.jpg
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IMG_1873.JPG
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Re: Trouble soldering SS to copper

Post by PeatyKeats »

Twisted Brick wrote: Wed Sep 15, 2021 7:43 pm
PeatyKeats wrote: Wed Sep 15, 2021 6:14 pm
So, to be on the safe side, you simply made a copper shim that fit flush with the SS ferrule, and used silver solder on the joint without tinning?
I assume you fluxed both side of the shim and the other necessary surfaces…
Thanks.
Yes, but I work mostly with Type L pipe which requires a slight reduction in ID for the ferrule to fit properly. I use a drill-mounted tungsten carbide cutting burr on the end of 2" pipe before cutting the shim off. A 5/8" shim fits the ferrule barrels nicely. After sanding my ferrule the reduced shims should slide onto it with very slight resistance. This encourages a complete 360* filling of solder. If you heat around the shim from the top down and feed the solder from the bottom, the solder will draw upwards and ideally give you a complete ring.

The shimmed ferrule will now slide into your fitting like a piece of pipe. I stand my pipe vertically onto the ferrule and like the shim, heat from the top down, about 1/2" above where the shim/ferrule terminates inside the pipe. Yes, all surfaces should be sanded and cleaned (I use alcohol) and fluxed (both mating surfaces). Just before applying solder I re-flux the joint, effectively removing any burnt flux. With the Harris silver solder this method has proved very solid with no need for tinning.
IMG_1769 copy.jpg
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IMG_1873.JPG
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IMG_1768 copy.jpg
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Thank you for the detail and pictures.
One last question for clarification.

You flux and solder the shim to the ferrule first, then fit the copper pipe over the shimmed ferrule and then reapply flux and solder, correct?

I was thinking about trying this, but wasn’t sure if there was a downside.
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Re: Trouble soldering SS to copper

Post by bronctoad »

+1 on re-applying flux just before applying solder :thumbup:

that's the trick that makes the joint seal first time.
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Re: Trouble soldering SS to copper

Post by Bee »

I'd think about getting different ferrules.

The short ferrules from sanitaryfittings.us are a slight press fit in a 2" type L. Look for "Tri-Clamp Short Ferrule (14WMP)".
You bevel the mouth of the pipe a little with a round file then put the flux on each piece press it in or use blocks of wood on each end and a hammer, then apply your solder. Leak-free the first time!
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Re: Trouble soldering SS to copper

Post by Twisted Brick »

PeatyKeats wrote: Thu Sep 16, 2021 4:17 am
You flux and solder the shim to the ferrule first, then fit the copper pipe over the shimmed ferrule and then reapply flux and solder, correct?
Yes. I file and clean off the soldered shimmed ferrule so it looks like the second pic before proceeding. Flux, heat and solder as before. If you heat your copper slowly, re-flux and carefully apply your solder at the correct temp, there shouldn't be too much excess solder to file off and will clean up real nice.
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Re: Trouble soldering SS to copper

Post by PeatyKeats »

Twisted Brick wrote: Thu Sep 16, 2021 8:52 am
Yes. I file and clean off the soldered shimmed ferrule so it looks like the second pic before proceeding. Flux, heat and solder as before. If you heat your copper slowly, re-flux and carefully apply your solder at the correct temp, there shouldn't be too much excess solder to file off and will clean up real nice.
Thanks.
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