Soldering vs Brazing

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Soldering vs Brazing

Postby yeastherder » Sat Jan 05, 2013 8:12 am

I have doing a lot of reading and thinking about the tools and materials I would need to build a copper pot still similar to the pintoshine design I have seen posted here. I have read the How to solder post and searched the forums but I haven't been able to find a clear answer to this yet.

A lot of what I read, people seem to use soldering interchangeably with brazing and that's where I am getting confused. Brazing is done at a higher temperature and with a higher content silver brazing alloy (solder) than plain old soldering is or so I have read. Plain old lead free solder melts around 400 to 600 degrees while brazing alloys melt at much higher temps.

So if I am building a copper pot still, do I want to braze the bottom and sides when joining them together or can I get away with soldering them? My concern is if a soldered joint will melt when i am making a run. After all you can solder with a propane torch and I plan to use propane as my heat source to fire the still. Any opinions on this would be much appreciate.
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Re: Soldering vs Brazing

Postby Maritimer » Sat Jan 05, 2013 8:38 am

Hi yeastherder,

Providing your boiler doesn't run dry, the temperature of the metal will not get much above boiling point, so you could solder that. You might have trouble using a propane torch, though, because the copper conducts heat away very quickly. MAPP gas would do the trick, but even better would be acetylene.

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Re: Soldering vs Brazing

Postby Usge » Sat Jan 05, 2013 8:46 am

If I remember correctly, much of that design uses rivets for strength and soft solder should be fine. The bottom...where the heat is...has liquid in it. This is what keeps it from heating to the point it would melt. So long as you don't boil it dry or run it dry...that solder shouldn't be a problem. It takes about 1200-1300 F to braze. That's when the copper is "cherry red". So, brazing..inherently means you are annealing the copper (it will be soft after you braze it, dent easily, etc) . And as was said above...copper soaks up the heat. It takes a LOT of direct heat to get it up to brazing temp.

Some people do/use a bit of both. ie., they braze certain joins/parts to make them extra sturdy. Like the bottom, the lynearm where it connects to the head, etc. If you decide to do that...make sure you do your brazing first. Because heating the copper to brazing temps will only melt the soft solder anywhere near it. You can soft solder all day long right next to a brazed join and it wont' budge.

Another old trick is to use a wet rag (or something to cool with) when you have an already soldered join or seam you are trying to protect. It works...up to a point.
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Re: Soldering vs Brazing

Postby heynonny » Sun Jan 06, 2013 8:27 am

Silver solder takes more heat than reg solder, but less heat than brazing. Its stronger than reg solder, prob a little less than brazed, but plenty strong. -hey-
  
 
 
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Re: Soldering vs Brazing

Postby yeastherder » Sun Jan 06, 2013 6:15 pm

Thats reassuring. Thanks for the info.
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