Silver soldering / brazing with propane

[Judo]

I did some reading and I had a go, now I have questions. Google gives a lot of contradicting answers and terminology, so I'm going to the source of all technical truth.... Land Rover owners. :D

Firstly, silver soldering = brazing?

Type of filler: I tried with silver bearing solder and flux (pictured below). Brass to Stainless. Is this solder OK for brass to stainless?

I was expecting to have to put more heat into it, but it wasn't very long before the flux was sizzling, so I added some solder. I think the first dab of solder went well.
I had prepared myself to add just a little solder and let it flow around like my research had told me. But in the heat of the moment (get it?), something happened....I got carried away and put heaps of solder on. :mad: ;) So I suspect this is part of my problem. I ended up with a small pool of solder inside the tube too. :angel:

I filled only where the metals were touching. As you can see the solder flowed vertically up the brass OK.

Heat / Thermal conductivity: I understand brass needs heating much more than SS to reach the correct temperature? The solder flowed all around and stuck to the brass really well, but not the SS. However the SS is thicker. Not enough heat on SS? Or is it another problem that caused the solder not to join with the SS?

So in conclusion, I suspect the first dab of solder was actually quite successful and I should have stopped, but the rest of my over filling ended up too cold. :confused: Thoughts?

Any other pro (or not so pro) tips before I try again?


https://www.aulro.com/afvb/images/imported/2013/09/926.jpg
https://www.aulro.com/afvb/images/imported/2013/09/927.jpg

[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.

[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?

[Judo]

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...


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. :)

[Rick1970]

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 :eek:
No wonder the boss whinges when I get the big boxes :D....about $500for a .5kg box.

[Ancient Mariner]

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:cool:

AM

[Judo]

I read this and learnt a few things.

Soldering (http://www.willingtons.com/mymac/soldering.htm)

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.

[isuzutoo-eh]

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.

[crash]

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.

[slug_burner]

If you have a gas bbq burner put your ss pipe onto that for extra heat. My dad would silver solder on the kitchen cook top to help his soldering iron along.

[Judo]

Attempt 2 with the same solder and flux was not very successful. Same flux problems - the flux is all burnt away in seconds leaving a black surface, but it takes ages to get the SS hot. The result is that the solder won't stick to the SS. Discovered there's a BOC not far from home, so Monday I will go to BOC and buy some better flux and maybe some rods to play around with.


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.

I tried the screwdriver trick, but the flux didn't get much of a chance to do anything before being rapidly spat everywhere!



If you have a gas bbq burner put your ss pipe onto that for extra heat. My dad would silver solder on the kitchen cook top to help his soldering iron along.

WIth my level of skill presently, I think it's best I keep the flux and solder away from the stove top!! I plan to get my rental bond back when I move out! :p

[Judo]

Went to BOC and purchased some of these.

https://www.aulro.com/afvb/images/imported/2013/09/369.jpg

BOC man said it's impossible to braze or solder stainless without an oxy. I also purchased a MAP gas blow torch - which he also said wouldn't be hot enough.

Then I did this first go with MAP gas and the 45% silver solder rods.

Still hot:

https://www.aulro.com/afvb/images/imported/2013/09/370.jpg

Cooled down and wire brushed only:

https://www.aulro.com/afvb/images/imported/2013/10/1029.jpg

Good enough for me! :)