Thread: Silver soldering / brazing with propane

tail about on the heat.

theres not enough heat in the stainless so the solder has flowed away from the stainless.

the stainless is a much bigger heatsink than the brass so will take more heating to get to the same temp as the brass. fitting.

you can see spots where the stainless has hot spotted onto the stainless and is trying to hold. in additon to the heat you may need a different flux to get it clean enough to solder.

when ive done braizing in the past ive used silver solder rods from the welding shops I normaly try to get 46% silver as ive had best luck with that,

the flux I normaly use is just the one the welding shop sold me years ago, the lable is gone off the bottle now, so not sure what it is

were you using map gass or a oxy set?

Originally Posted by Blknight.aus

tail about on the heat.

theres not enough heat in the stainless so the solder has flowed away from the stainless.

the stainless is a much bigger heatsink than the brass so will take more heating to get to the same temp as the brass. fitting.

you can see spots where the stainless has hot spotted onto the stainless and is trying to hold. in additon to the heat you may need a different flux to get it clean enough to solder.

Got it, thanks. You might be right with the flux. Will see next time...

Originally Posted by R Miller

when ive done braizing in the past ive used silver solder rods from the welding shops I normaly try to get 46% silver as ive had best luck with that,

the flux I normaly use is just the one the welding shop sold me years ago, the lable is gone off the bottle now, so not sure what it is

were you using map gass or a oxy set?

Propane blow torch. Similar to MAPP, although not sure if it's identical. MAPP looks like it might be a mix of propane and other.

I watched some videos with people using flux covered rods and they also look suitable, but I guess that's where I'm a little confused. The only rods I've seen are for an oxy, which I don't think will melt with a blow torch. If you're saying silver solder rods then that makes sense. I'll continue with my solder for the moment anyway. Thanks.

Originally Posted by Judo

I watched some videos with people using flux covered rods and they also look suitable, but I guess that's where I'm a little confused. The only rods I've seen are for an oxy, which I don't think will melt with a blow torch. If you're saying silver solder rods then that makes sense. I'll continue with my solder for the moment anyway. Thanks.

Yes, silver soldering/brazing with a propane torch would be a very slow process. I have done it when an oxy set wasn't available, but the fittings were small, held the job with bricks (lower heat transfer than using a vice to hold them), and zero wind. One joint still took about 15 + min.

I have used the flux covered rods and personally much rather a separate flux.

Brass is a PITA to silver solder IMHO....stainless steel s/solders beautifully tho.

Ran out of silver solder rods at work last week, and the only ones I could find in town worked out quite expensive, $70 a pack....5 rods
No wonder the boss whinges when I get the big boxes ....about $500for a .5kg box.

Comweld 965 is a really good flux for soft solder (stuff that will melt with a soldering iron} Brown tip silver solder for copper no flux needed but needs silver solder flux copper to brass. Eutectic pink flux coated ideal for hydraulic fittings. brass. copper .stainless .monel .steel but pretty dear. LPG or oxy ok
You can do very neat silver soldering on copper with TIG with a small heat affected zone but need a fair bit off experience for dissimilar metals If soft soldering clean is essential and try and tin each part separate if possible

AM

I read this and learnt a few things.

Soldering

First thought is, that with better technique I will be able to solder the brass barb onto SS tube OK.

If improved technique doesn't help, I suspect better flux is a good place to start. The link above says if the flux burns black and sooty, it's too hot / no good for flame. I fear I had this problem - the flux was ready almost instantly, but the SS was not hot enough. Heating it more ruined the flux. Second to this I found further info on the solder I have and it melts at 220C and presumably the flux is matched to that solder (it came in together in a pack). That doesn't seem very hot to me...

The site also lists Comweld 965 as the "best for any flame based soldering. I have not used anything better ever". Comweld 965 sounds like a good tip AM.

Cheers.

Stainless has lower thermal conductivity than brass, this means that if the size of the materials is equal the SS will keep the heat localised and have less heat sinking. But you have a tiny pimple of brass on a big lump of SS, so you'll need to heat the SS for longer to get it to the same temperature.
You can add the flux after the metal is up to temperature too, using a wooden spatula or a screwdriver (just don't solder it on!), but be careful as it may spit and spatter into your eyes or onto your skin.

Since the barb is close to the end, would it be worth while heating the SS tube from the inside? then once up to temp put the brass barb on.