A friend wants to braze copper pipe to stainless steel for a
project. He’s looking for food safe brazing rod and more info. on
brazing stainless steel.
He has access to an oxyacetylene torch.
Suggestions?
Thanks!
Elaine
-
you need the right reactive flux specifically for stainless steel.
Johnson Matthey make a good one in 500 gm pots in powder form -
any silver based hall marking grade brazing rod will do, tho a
cheaper option is ordinary silicon brass brazing rod, it depends
where the brazed joint is and how big it is. -
Your friend will find that the copper will be the real problem
when in contact with food.
Frying in olive oil will be fine, but say cooking acidic fruit will
eat the copper away. Tho copper pots were or still are tin coated by
melting the tin onto the copper. not electro plated.
You will get a silver solder to do that. I have soldered S/S many
times with silver solder “for base metals”. Easy flow solder and flux
will do it. I don’t dilute the flux, just warm the solder and object
and melt the flux powder on to the surface of both to give a good
blanket to keep the oxygen out!
Hamish
My suggestion would be to have it done professionally by a welding
shop, the word that scares me is “food safe” I worked in factory
that made food safe printing presses for a while, and there are so
make things that aren’t food safe, even the wrong kind of stainless
steel isn’t food safe. Even 316 stainless that isn’t passivated,
really isn’t food safe. So please, on the side of caution, get it
professionally done, it will probably be cheaper than the
brazing/welding rod.
Chris
Elaine- I’d just use silver solder and paste flux for that. Silver
solder should be food safe. However bare copper, not so much if it’s
coming into contact with acidic foods.
Have fun and make lots of jewelry.
Jo Haemer
www.timothywgreen.com
A friend wants to braze copper pipe to stainless steel
Search “Harris Brazing Products”, they have the brazing rods, fluxes
and how to videos. Very helpful website.
Regards,
Jim Sivertsen
United Technical Dept.
Hello Elaine,
I would recommend using a silver brazing alloy for this joint. If you
are based in the US use an AWS BAg 7 specification alloy or in Europe
use an EN1044 AG103 specification alloy. These two alloy
specifications are available from many different suppliers under
their own trade names. The key when joining any stainless steel
alloy by brazing is to use a specialist stainless steel brazing flux
to remove the surface oxides off the steel. Any good welding/brazing
consumables supplier should be able to advise you on this correct
flux choice.
Charles Allenden
However bare copper, not so much if it's coming into contact with acidic foods.
Just boiling water, so should be okay, right?
Elaine
CreativeTextureTools.com
I’ve not brazed stainless to copper, but I’ve done stainless to
stainless… We used silver solder for that, so assuming that’s food
safe, then I would try that first. Be careful not to overheat the
steel because stainless will “cook” pretty easily.
Just boiling water, so should be okay, right?
There will be some corrosion issues, how fast and how bad will depend
on what the water chemistry is like. Tap water is not pure water and
has dissolved minerals in it. These minerals make it conductive and a
silver / copper / stainless battery will be set up if the stainless
is fully passivated then there will be minimal stainless corrosion
but if the passivation layer is damaged there will be corrosion.
Silver is the most noble of the metals in the mix so the copper will
also corrode, but because the silver will likely have the smallest
surface area exposed to the liquid there will likely be minimal
effect from it but, looking around the braze joint for evidence of
corrosion might not be a bad idea.
James Binnion
James Binnion Metal Arts
I’d ask at restaurant kitchen equioment suppliers who does custom
work, Lots of kitchen equipment is custom built, customized, or
modified in local shops They;d have the practical familiarity.
Just to pick up on what James has said about corrosion issues. The
biggest potential problem when brazing stainless steel and/or copper
in systems where they are going to be exposed to hot water is
de-zincification of the brazing alloy. Experience in the hot water
boiler industry has shown that where a cadmium-free silver brazing
alloy with a silver content of 55% or greater is used then this
problem does not usually occur. In a previous role where I advised on
this type of joining and investigated failure the majority of the
corrosion I saw usually initiated in an area where the brazing flux
had not been completely removed after the joining operation had been
carried out. The residual brazing flux traps water beneath it
allowing and the creation of this static area of water allows
electro-chemical corrosion to take place.
Charles Allenden