Silver Soldering Stainless to Copper

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Has anyone on here done this? I know its do able, but I haven't been able to do it regardless of what I try doing. I have some 46% silver solder, and I'm trying to use the paste that comes with it but doesn't seem to hold on to copper, but work for the stainless. The closest that I've gotten it, and only worked on one spot, is I per-soldered on some regular plumber solder on the copper tubing with the flux that it goes with it. And then Pre-soldered the stainless with another flux and the 45% solder, and then with using the 45% solder, I would manually manipulate the puddle to bridge, with extra solder. I'm really trying to keep this as clean looking as possible, and I know that isn't it. So my question is, what kind of flux do you guys use to join dissimilar metals like that?Owner at: www.re-speed.comLike us on Facebook: https://www.facebook.com/respeed
Reply:You should be able to silver solder the stainless to the copper.My thinking is do not tin the copper with regular solder.Clean the stainless and copper with a stainless steel brush.Flux both the copper and stainless with paste flux (I like Harris "Stay-Silv" silver solder flux).Get the torch on the pieces and when hot enough add the silver solder.Good luck,John
Reply:You need the correct flux.ESAB has a great line up  http://www.esabna.com/us/en/products...m?Category=181Have a look at that overview; the one you want may be this one  http://www.esabna.com/us/en/products...roduct_ID=1024Best O Luck!Rick V 1 Airco Heliwelder 3A/DDR3 CTC 70/90 amp Stick/Tig Inverters in Parallel1 Lincoln MIG PAK 151 Oxy-Acet
Reply:++ on the Stay-Silv.  Good stuff. DanD.
Reply:Not much bridge action with 45% silver.   Proper fit up is important.
Reply:do you need the strength of silver solder (braze?).How about 50/50 solder at lower temps?  (unless this will be subject to a lot of vibration or high pressure).CLEAN is important.  Wipe both parts with 91% isopropyl alcohol.  Scuff up both pieces with a clean stainless wire brush or red 3M scuffy pad.Use the right flux for the solder/braze material and temperature.Here are some of the samples of soldering, brazing (silver soldering) and welding from my recent Mastering the Torch course.  I think the left-most sample, near the top, is copper and regular cold-rolled steel with silver solder (hard soldering/brazing).  Plenty of these samples are stainless.  The stainless should need a cleaning (acid) flux.  I haven't tried it myself, but I've heard that apple cider vinegar works in a pinch:Kevin / Machine_Punk from The Aerodrome Studio - Lincoln PowerMIG 210 MP - Meco N Midget w/custom welding station - Vintage Victor 100Current Projects: The Aerodrome Studio
Reply:Not much of a help because I don't know what we were using but, I worked at a place were we had to silver solder copper tubes into stainless blocks.  We also used the same solder and flux to do stainless to stainless joints, and brass to copper joints, and we may have done brass to stainless joints as well.  No major prep work was needed except all cutting oil was off the pieces.This was all done with an O/A torch.  The blocks were mostly 2"x2"x2" square and took a bit of preheat with the torch turned up pretty good, we mostly heated to a dull red then turned the torch down to a soft flame and worked the joints until the solder flowed.Last edited by Oxford; 12-28-2013 at 09:24 PM.
Reply:If you can find some of the premixed paste flux that has a fine silver solder powder mixed with it, that has always worked for me.... but you have to have a nice fit-up.  Once you get the solder/paste mixture on both pieces and fitted up, just play the torch flame over the connection until you see the solder flow out.  This makes great looking clean connections.  You can make your own solder/paste if you get the paste flux. Frys Electronics carries it.   Melt some of your solder into an aluminum tube to create a decent sized silver plug, remove the plug from the aluminum tube, then rub the plug against a file until you get a good pile of silver filings and mix with the paste flux.Miller Syncrowave 350Millermatic 252/ 30A spoolgunMiller Bobcat 225g w/ 3545 spoolgunLincoln PowerArc4000Lincoln 175 Mig  Lincoln 135 Mig Everlast 250EX TigCentury ac/dc 230 amp stickVictor O/AHypertherm 1000 plasma
Reply:Thanks for everyone's input on this. I needed to get this project done today, and wasn't able to source better flux in time to get this done. After much playing around, I found out that I was able to actually weld the stainless to copper with that 45% silver solder, no flux, but I used the TIG welder to work the materials together. Came out much better than expected! My main goal with all my projects, is that I like to have my welds looking as best as possible, and not being to properly flow that solder in there easily and cleanly with an open flam, was my biggest issue. It wouldn't have been as big of a problem if I had something to go around the soldered joint to clean up the excess, but due to the way the components had been laid out on there, I could have only done it by hand. This piece needed to be fully polished afterwards, so anything to reduce that time is a huge factor. That was my main reason for loving TIG welding in the first place (cleanliness of weld).Owner at: www.re-speed.comLike us on Facebook: https://www.facebook.com/respeed
Reply:Machine Punk - ever try SSF-6 silver solder from Muggyweld?  A local artist here in Chicago swears by their flux-coated rods (56% silver) is really nice and the net strengths are 70 ksi.  He produces a lot of stainless and mild steel art.  I am not pro solderer by any stretch and have only used traditional 50/50 tin-lead solder.  I would appreciate you sharing any of your experiences with SSF-6.  I want to try some of the flux-coated rods!  http://muggyweld.com/all-products/silver-solder
Reply:"Discovery is to see what everybody else has seen, and to think what nobody else has thought" - Albert Szent-Gyorgyi
Reply:Originally Posted by ManoKai
Reply:Originally Posted by roadkillbobbshe can clean my pipes any day...lol
Reply:Propane works ok with lead/tin solder but for silver solder you need at least MAPP gas or OA.What process did you use dj55b? I would tin both pieces with silver and use white stuf flux.I have to go check out Savanahs rack now, I mean how she racks balls I mean how she racks 9 balls. Ah never mind.Last edited by Insaneride; 03-14-2015 at 11:20 AM.
Reply:If you can TIG, EZ Weld TIG wire from DaveBro Inc. will join SS to Cu, SS to Mild, Mild to Cu, and CI.HF 98233 Stick/TigHF  95136 PlasmaEastwood TIG200Eastwood MIG250Damn, I cut it twice already and it's still too short!