S/Steel to Copper Brazing

I don't think you are going to have a lot of luck brazing copper to stainless, but I'm certainly not an expert on that subject. However, I had an identical problem a while back on a vacuum furnace. It was a barrel shaped chamber so I ran multiple loops of copper tubing around it (can't remember the exact spacing...I'm thinking it was about six inches). I then epoxied the tubing to the stainless. It wasn't the prettiest thing to behold, but it worked like a champ. BTW, the furnace was ramping up and down from ambient to 750C if I remember correctly but the water in the copper tubing kept the cured epoxy reasonably cool. Hope that helps.

The best procedure may be to determine how the original copper tubes were fastened and replicate that material. It will depend on how hot the furnace wall becomes during operation. Soft solder (eg SnAg) is the easiest to use with an acid flux, but will melt if the temperature goes above about 400 deg.f. A silver solder such as easy-flo 45 will be good to about 1000 deg. f, but is more difficult to use.

hi,

I don't think its a big problem. Just align copper tube and Stain less tube and heat both with gas cutting set up to redness. Take a suitable filler rod and dip it in flux and melt it over the joint ( ss-copper joint) all around. After full joint is covered with molten material, allow it to cool at room temp. This type of joint will sustain a presurre of about 7 - 11 kg/ sq. cm. Try this and have a nice time.

virendra

Well, I more-or-less agree with guest (post3)... but, upon reviewing some "defect" data (in ASM Volume 17) ... then realizing that you didn't specify WHAT GRADE of SS, I am more inclined to suggest some of that old "Ounce of prevention..." philosophy first. Learn from others what THEY have done, then proceed with an educated approach.

Your options might include changing your piping (cupro-nickel?) so as to utilize a much better brazing approach.
See: All Stainless Nickle Brazed Plate Heat Exchangers at~
https://www.globalspec.com/FeaturedProducts/Detail/SWEP/All_Stainless_Nickle_Brazed_Plate_Heat_Exchangers/19719/0

and then, perhaps call 440-349-5100 to confer with these experts...
https://www.brazesolutions.com/?gclid=CLeByqf0w5ECFQd4Hgod0WECyg

Surely SOMEBODY knows exactly what the BEST solution currently available is... instead of taking the old 'shotgun' approach.

Best of luck with it.

Soldering copper is a tricky business in itself. It's hard to do it without having leaks let alone doing it with stainless steel.

I think a better solution would be to weld a Stainless Steel threaded nipple to the tank and put a flanged fitting on the copper tube. Copper tube you can get a tool that will flair the end to hold on a slip-on fitting to thread into the threaded nipple on the tank.

evidently you are not a plumber. soldering copper to copper is one of the easiest things todo. just make sure the joints are clean and well fluxed, add heat and solder, the solder will flow where the heat is.

copper to stainless? a little more tricky, but can be done.

oilcan13

No, I've never had to do it but I've heard talking about it by my Dad who was working on a swamp cooler about how the solder doesn't always form a seal on the copper.