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Silver solder or braze

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Eric Cox19/01/2011 09:54:11
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When building a boiler or fastening two components together do I use silver solder or braze.
JasonB19/01/2011 12:53:07
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Silver solder, though if you are from the US it would be called "silver braze" would be the best option.
You can use Brazing also called bronze welding to join materials together but best not on a boiler as some of the brazing rods react to steam over time. It requires more heat than silver soldering so you really ned oxy-acetalene or at a push carbon arc rods on an arc welder, I think its also possible with tig using a specific rod.
Jason
Richard Parsons19/01/2011 13:06:11
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Which to choose, silver solder or brazing? It all depends on which metals you are joining together. What you have to know is the melting points of the materials involved. Copper has a melting point of around 1083°C. Brazing rods have a MP about 900°C, a bit too close for comfort, but if you are doing a furnace braze you could do it if your thermostats are good.  What about brass?  Well brazing rods are an alloy which is brass, so you would use a lower melting point rod. Probably silver solder out of choice

Steels, I often braze mild steel. A well made braze has some 80% the strength of mild steel.I have also brazed cast iron but you have to pre-heat the whole casting before doing this and let it cool down very slowly.

Special steels are designed to be brazed.One I think is Reynolds 853 (I may be wrong with the number) when brazed does not go brittle which it can do when welded.

Stainless Steel, I believe that it is illegal to braze or silver solder stainless in the U.K.The Gnomes of Elfin Safety do not like it.

Edited By Richard Parsons on 19/01/2011 13:08:09

Richard Parsons19/01/2011 13:17:10
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JasonB our postings crossed. I use Propane/Butane and compressed air for brazing it works well but like Oxy Acetelene you need a carburising flame.
There is a sort of myth about hot watwer disolving the zinc in brazing rods.I buy rods which aregauranteed proof against that problem.
Bowber19/01/2011 18:17:58
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I was always told "I've told you a thousand times is Bronze welding, brazing is silver soldering!"
Then I'd be clipped round the ear

Silver solder is good for close joins, so parts with a free sliding fit or close together etc can be silver soldered with the solder working it's way through via capillary action.

Parts that don't have a close fit will need to be bronze welded or brazed if you want to call it that.

Reynolds did make tubing for bronze welding I think it was 731 though and they make bicycle tube kits for custom made bicycle manufacturers with the same properties.
I think we used sifbronze mainly with a gas fluxer, better than powder flux as it didn't run off down the tube with the braze following it.

I just use a TIG now as the gas bottles cost too much to keep the rent on these days for hobby use.

Steve
KWIL19/01/2011 19:02:12
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Reynolds 531 Tubing was the start of it.
Speedy Builder519/01/2011 20:08:57
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Hi Richard P - Silver soldering stainless steel - Illegal ??
Not so sure about this advice.
Looking at Johnson Matthey's latest information:-
Their chart shows the Silver-Flo range of silver solders being suitable and
the use of Easy-Flo silver solder flux with Tenacity-5 for larger SS parts requiring extended heating cycles.
The silver flo range is Cadmium free (Cadmium bearing silver solder is not illegal, but not advised).
Hope this helps.
JasonB19/01/2011 20:12:35
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I've got a nice 531 smooth fillet brazed mountain bike, my uncle was a frame builer. He was certified to work with all their tube sets (and Colubus)having had test joints approved.
J
Nicholas Farr20/01/2011 00:22:04
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Hi,
brazing is joining two metals with hard solder that has a high melting piont, and having a gap of between 0.04 and 0.20mm. Silver solder being one of them.
 
Braze welding has a higher temperature and uses brass filler rods, of which there are many types.
 
Brass or bronze welding is as it says it is, i.e. the welding of brass or bronze.
 
Richard, when using oxy-acetylene you should use a soft neutral flame for brazing. A slightly oxidising flame may be used, and is preferred when braze welding or when welding brass or bronze
.
A carburising flame should be used for hard facing and when welding cast iron, using cast iron filler rods.
 
Regards Nick.

Edited By Nicholas Farr on 20/01/2011 00:23:03

Edited By Nicholas Farr on 20/01/2011 00:25:29

Edited By Nicholas Farr on 20/01/2011 00:28:05

Edited By Nicholas Farr on 20/01/2011 00:28:57

Nicholas Farr20/01/2011 00:22:04
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Sorry double posted.
 
Regards Nick.

Edited By Nicholas Farr on 20/01/2011 00:24:33

John Olsen20/01/2011 08:53:46
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I got a lot of fun as an 18 year old trainee watching another trainee try to braze a nipple onto the end of a cable for a scooter. He would turn up a cylindrical brass nipple, cross drill it for the wire, then take it to the welding bay and try to braze it onto the cable. Annoyingly, just as it all seemed to be getting hot enough, the nipple would go and melt on him. He tried this several times before somebody took him aside and clued him up as to what the problem was.
regards
John
KWIL20/01/2011 09:12:09
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Nick, when you have to edit, you can also edit out your previous "Edited by...." as well !!
Bowber20/01/2011 20:35:26
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Posted by Nicholas Farr on 20/01/2011 00:22:04:
Hi,
brazing is joining two metals with hard solder that has a high melting piont, and having a gap of between 0.04 and 0.20mm. Silver solder being one of them.

Brass or bronze welding is as it says it is, i.e. the welding of brass or bronze.

I can only go by what I was taught, I've still got the twitch Maybe the ringing in my ear was why I miss heard.
Steve

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