Weld Copper to Stainless

[salem747]

Hi Guys,

I need to connect a 2" copper fitting to a flat piece of stainless. I have a Syncrowave 200. I have tested fusion welding the two together but the puddles don't want to mix, as I suspected.

I thought for sure I could just use JB Weld but that didn't stick to the stainless.

I want the joint to be pretty strong as a tall apparatus will be sticking out of the fitting.

Is there any way to TIG this (PS I am brand new to TIG)?

What about silver solder?

PS Yes, this is to connect a copper still to a mash pot!

[sn0border88]

Silver solder is perfect for what you want to do.

[WenValley]

Good luck with your still...

[Vinnie]

Can be tiged with silicone bronze but not a job for a beginner tig welder.

[Greyhorse]

What about a threaded fitting of the same metal welded on to each piece and then screwed together?

[weldbead]

What about a threaded fitting of the same metal welded on to each piece and then screwed together?

poooosies way out...an you still gotta solder or braze the copper side...

[MoonRise]

Braze the pieces together.

Because short of some sort of 'solid-state' joining method (explosive welding and such), there is no real way to arc (or gas, or laser, or EB) weld two such dissimilar metals together.

Pay attention to the brazing alloy and possible fluxes involved, as not all such may be food-safe.

Maybe an alternative could be to weld or braze the appropriate flange-fitting halves to their similar metals and then make a bolted and gasketed flange joint between the two?

[rhunt]

Yes on the silver solder. Keep most of your heat on the stainless. Bob

[Fegenbush]

...short of some sort of 'solid-state' joining method (explosive welding and such), there is no real way to arc (or gas, or laser, or EB) weld two such dissimilar metals together.

I beg to differ. Not only do I believe that it can be done, I have seen it done and x-rayed.

[prop-doctor]

i have welded my copper template to a SS blade by accident

[prop-doctor]

doin some reading
( google search welding stainless to copper turn up some scrolled down found one
" welding-copper with intense heat localized heat input "
2/3 down article PWL# 027 Weldability for weld repair,copper to stainless
.welding-advisers.com/PRACTIAL_WELDING_LETTER-PracticalWeldingLetterNo.27
grrrrrrrrrrr cant get link to work

[Ries]

I have TIG brazed, with a silicon bronze filler rod, lots of copper, brass, and bronze to stainless. Works fine.
Copper is a lot easier than brass, especially if it has zinc and lead in it, like CDA 360 does.

Copper takes a lot of amps, though. You will probably need to turn your welder up all the way.
I would start the arc on the stainless, feed in silly bronze, and wash it down onto the copper.

[salem747]

So I went to get silver solder and talked to a buddy at the LWS. He had silver solder and some Bernzomatic "metal solder" So I bought both to try the metal solder stuff. It was $8.99 vs $54 for silver solder.

I didn't realize that silver solder requires and OA torch. I only have Oxy Propane, but he figured I could use my TIG for the heat source.

The TIG brazing sounds cool I will see if I can get some of that silicon bronze rod. Now in brazing you should be melting both host metals, right? Then add rod as filler?

Anyway I attached it with the "metal solder" and did a test run with water, seemed to hold up OK. I need to patch a few leaks in my copper soldering now that I have run water through it. I will test the whole thing tonight on some apricot mash I have been fermenting for a couple of weeks. AND we have peaches and plums that are alomost ripe in the garden!

[MoonRise]

Umm, no.

In brazing, you heat the 'parent' metals just enough to be able to have -them- melt the brazing filler.

Just like soldering, except hotter.

No melting the parent materials. (that's called "welding" )

And if the low-cost Bernzomatic "metal solder" is the stuff I'm thinking of, it is a solder that is either solid wire (may be a lead-based alloy, which you really-really don't want to use for food stuff) or an acid-core lead-based solder (again, which you really-really don't want to use for food stuff). So not the right stuff for your purposes either way.

By me, TSC has (had?) some bare phosphor-bronze brazing rods (possible also some flux-coated ones too). Lowes and HomeDepot also have (had?) similar.

You probably do want brazing rods and not "solder" there.

[BCTimberwolf]

You're making this too hard. I used compression fittings and simple gaskets to fit up a SS part on my SS still and then a compression nut on the copper line. You could even use high temp silicone instead of gasket material.

[salem747]

I tried with a local plumbing wholesaleer for parts to do this and didn't have any luck. I guess if I researched and found the parts I wanted then just ask/order those it would work better. My whole still is copper, made of 2" copper pipe so that is what I need to connect to the SS pot. The "metal solder seems to work. It is actually around the outside of the connection too so there isn't really any interaction with the vapour going by.

[prop-doctor]

with practice it can be done ----
will be Hot and Fast Tig set just like i weld SS ,didn"t have a big piece of copper or smaller SS
was running about 120 amps my SS was toooo thinguess in .020 ,copper .045
needed both the same thickness and practice practice but could be done
sorry crappy cell pics

[VPT]

I'll have to give this a try. I've accidentally welded aluminum to stainless with a very brittle but ok looking weld before.

[sn0border88]

Looks like a situation where high peak, low frequency pulse welding would be ideal.

Something like:
Peak 180-220A
Background 5%
Hz .3-.5/sec

[prop-doctor]

all the amps were needed to puddle the copper
but when it did you better be ready to move
the SS was to thin just sucked right up, with same thickness materials could run a nice bead
just didnt have enough scrap copper to play with
any one got some test coupons to play with would like to see more tests

[CosmicRambler]

Sounds like you already got it done but there is a method I will always try in those situations.

Get both materials in a round form so it can be like a socket weld. In this case I would put the stainless as the smaller insert piece. Make the socket pretty deep, flux up the parts a ton and pour lead free solder about like lead'n up a drain line cast iron part. You should get something like a mechanical joint that is leak free. Should work as long as your application is below melting temp of solder.

Could use lead if you did not have a booze application.

Biggest trick is how to keep the pour from leaking, a preheat and hammered tight fit up works, inner part cold, outer hot is better yet before hammering her in. Can try the packing method used in plumbing pours too. Method does work when nothing else you try does. Or you ain't got the right equipment for something fancy.

[jdchmiel]

silly question - why do you need to weld the copper to the stainless? Why not weld a female threaded stainless part to the stainless, and then use a male threaded copper piece on the copper side.