Copper to Sheet Metal Brazing

Date 04-16-2008 13:01 Edited 04-16-2008 13:06

I have had good luck with using these folks....

http://www.harrisproductsgroup.com/

Search around on the site, they have filler metal selection charts to help with choosing fluxes and even some detailed instructions.

Don't know how strong the joints need to be, but have you looked into some silver solder? I think you need to be around 1450-75F to work with it. I used that to join HVAC stuff back in my college days (steel to copper).

Here is a filler selection chart off that site...

http://www.harrisproductsgroup.com/consumables/FillerMetalChart.asp

By DaveBoyer (*****)

Date 04-17-2008 04:04

Rick, what problem are You having?

Copper conducts heat much faster than steel, unless You are melting the copper, You are probably not getting it hot enough.

If You are having problems with the copper melting, You might try a lower melting temperature filler.

Any flux that works for brazing steel should be fine for brazing copper to steel.

By Rick Gush Date 04-17-2008 05:31

Thanks John and Dave,

I'm off today to tour the hardware and welding supply stores in Genova. I'll look to get some medium grade silver filler rods and some low temperature silver brazing flux, as recommended on the Harris site.
My problem was that no matter how I slathered on flux, the brass filler would stick well to the steel sheet, but not really stick well to the copper. It did stick to the copper a few times in some small places where there were particularly jagged edges, and that made me think the surface of the copper might be oxidized sufficintly to retard filler metal adhesion, but no matter how I polishd the copper before brazing, the filler still didn't stick.

I'll report back with an update after I try the new filler and flux. I wil also try the silver filler with the old flux.

I very much appreciate your help, and to return the favor I could give expert advice on agriculture, gardening, aquariums and Italy. Ha! If there's anything I can do for you, I'm at rickgush@gmail.com.

By ravi theCobra (**)

Date 04-17-2008 15:43

Start out with 45 % silver alloy and regular pre mixed ( creamy ) flux

By DaveBoyer (*****)

Date 04-18-2008 02:34

Rick, You are not getting the copper hot enough, that is why the filler won't stick to it. You should be able to get filler rod from a HVAC distributer, they are copper silicon and may have silver as well. These will work without flux on copper to copper, but need flux for copper to steel. What We use here in the US is a flat strip, often with a trade name like Sil Flo, Sil Fos, or something similar. If there is a number from 0 to 15 following the name it is probably the silver content. Silver allows the material to have some working range in temperature, a sort of plastic state between fully melted and fully solidified. This makes it more tolerant of joint fitup. The copper will need to be at dull red heat or hotter for these rods to work.

A lower trmperature alternative is soft solder, 50/50 lead tin or lead free plumbing solder. I prefer to use a "Tinning" flux with these, particularly if soldering to steel. This type of solder melts in the 400+ F range. If much strength is needed the joints will need a fair ammount of contact area, as the solder is, as the name implies, soft.

By OBEWAN

Date 04-18-2008 14:05

We routinely join copper sheet metal to stainless steel sheet metal for a jet engine part. The two can not be welded because the copper causes the stainless to crack. We use silicon bronze filler wire and TIG braze/weld. The wire has an industry trade name and is called Everdue. It would probably work well for your application.