Thread: Brazing/silver soldering brass and steel

Silver solder only for stainless...
I would silver solder only the brass as well, but that’s just me

Originally Posted by twr7cx

Thanks for the responses. I was ignorant and had previously assumed that brazing and silver soldering where two terms for the same process.

Soldering, as a process, wets the metals, but does not key into the parent metals.
Brazing has keying at the metal surfaces, hence the filler and the parent metal alloy at this joint.
Real world, most people get the idea whichever term you use.

As for the fluxes, choose one as per filler material manufacturer's recommendations. Unlike filler materials, there is little in the way of specifications for fluxes (that I'm aware of), but you'll need to know what active ingredients they use (eg flouride), and the flux should remain active at the temperature at which the filler material melts.
FWIW, people often refer to coated fillers by their flux colour. Realistically, there is no convention here, and a white fluxed rod, a blue fluxed rod, and one with pink and blue polka-dots may all have the same metallurgy... But try telling an old boily/engineer that the comcoat rods with the pink flux are the same as the same spec rods with a white flux, and you'll be in for a bit of an argument.

Originally Posted by Rick1970

You let it flash off and/or dry off with compressed air obviously. But yes, had the odd unexpected flame up when got sidetracked, usually talking when should have been concentrating .

I said gases , not flame or flame/flare up.

google it. Can be fatal

Chlorinated brake cleaner makes phosgene IIRC.

Originally Posted by Rick1970

Stainless silver solders beautifully.

It's really easy to stuff it up, you can oxidise the joint badly as the stainless dosen't dissipate heat well.

If using stainless use 'pickling paste' and at a minimum 45% silver brazing rod and flux.
The flux I've been using for the last couple of years actually turns from green to white when the temps roughly correct.

Using 15% and 45% silver solder is technically brazing, not soldering even though that's what we all call it.

Just remember that 45% silver doesn't fill voids near as well as 15% that is used on copper/copper joints, but it capillaries really well if you get your heat right and makes for a very strong joint if the parts have a good fit.

Originally Posted by rick130

It's really easy to stuff it up, you can oxidise the joint badly as the stainless dosen't dissipate heat well.

If using stainless use 'pickling paste' and at a minimum 45% silver brazing rod and flux.
The flux I've been using for the last couple of years actually turns from green to white when the temps roughly correct.

Using 15% and 45% silver solder is technically brazing, not soldering even though that's what we all call it.

Just remember that 45% silver doesn't fill voids near as well as 15% that is used on copper/copper joints, but it capillaries really well if you get your heat right and makes for a very strong joint if the parts have a good fit.

Yeah, 45% is what we use. 99% of the time we are just joining steel/steel (hydraulic fittings)

Originally Posted by uninformed

I said gases , not flame or flame/flare up.

google it. Can be fatal

Interesting.
Think I will be checking the label on the parts cleaner we use......

Years ago it was always cut down 20L drums with Petrol in them that we used, tho that’s kinda frowned apon these days.

Originally Posted by Rick1970

Yeah, 45% is what we use. 99% of the time we are just joining steel/steel (hydraulic fittings)

I used to do a lot of work on industrial ice machines a long time ago.
The tubes the ice forms on are over 1m long and about 150mm in diameter with stainless tails out the top going onto copper.
I had some higher % silver rod once (60%??) and god it was good to use.