Steel to copper brazing.

[josan6]

Trying to brazing a steel to copper connection, do I have to use a kind of flux or is correct do it as a copper to copper?. I use oxi-acetylene torch, and use silfox solder.

Thanks for comments.

[R12rules]

Originally posted by lmtd
It is NOT correct to do it as copper to copper.

Clean it REAL GOOD, don't touch it or blow on it, silver paste flux and 35 or 45% brazing wire. I like the 45% myself.

AMEN!


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[fixerup]

I have had the best results with paste flux and 45% silver solder.Make sure your copper and steel are real clean then get your tubing warm with your torch and apply your flux.I never had good luck applying the flux to cold metal.Keep most of your heat on the copper when it starts to flow move your heat towards the steel this will draw the solder up into the joint. Watch out and don't let the steel get cherry red.

[Wild Leg]

Originally posted by josan6
...brazing a steel to copper connection...

Silphos contains phosphorus.
Phosphorus is not intended for use with steel.
It might stick to steel, but it causes the steel to become brittle. It's a leak, waiting to happen.
Use 45% instead, with the proper paste flux.

Clean everything.
Keep excess flux out of the system.
Coat the tube & fitting with flux, then slip it together.
(Part of the job of the flux is to protect against oxidation while heating.)
Watch the flux. It will indicate temperature.
At 212, the water boils out and the flux becomes dry. Keep heating, slowly.
When the proper temperature has been reached, the flux will turn clear & quiet.
Don't overheat.
Practice, practice, practice, on some scrap.

(Sorry, R12rules, I did a search & many, many unrelated threads showed up.
Including, "Who wants to argue with me?".
I thought I might help Josan6 narrow it down a little.)

[thehumid1]

Originally posted by fixerup
I have had the best results with paste flux and 45% silver solder.Make sure your copper and steel are real clean then get your tubing warm with your torch and apply your flux.I never had good luck applying the flux to cold metal.Keep most of your heat on the copper when it starts to flow move your heat towards the steel this will draw the solder up into the joint. Watch out and don't let the steel get cherry red.

Thats the real trick to it i think.

[hi-tork]

all good advice, don't touch it because of the oil on your skin...will screw the whole thing up...

[frozensolid]

Stay silv 45 comes in sticks with the flux on it. I’ll never go back to coils of silver again. That stuff is great.

[icemeister]

Originally posted by frozensolid
Stay silv 45 comes in sticks with the flux on it. I’ll never go back to coils of silver again. That stuff is great.

I've used those blue flux-coated sticks for a couple of years now. I love them, too. I still have the wire and paste flux in the truck but I can't recall when I used it last.

[markwolf]

colored pictures too.. http://www.jwharris.com/jwref/procs/