repair of brass to copper steam heat coil

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Hello, I could use some help with the repair of this heat coil. It is a cast brass piece that is brazed to a copper coil assembly. The copper coil piece has a hole (1/8")and I've tried using silversolder 15% with no good results.Also tried making a fishplate type plug to lay over hole.Thuroughly cleaning with a file and preheating tube before placing plate to cover hole and attempting weld.The silver solder just rolls of the original copper tubing,yet it attaches to the copper piece placed over top of the hole.The solder looks dirty once it is melted onto the tubing.Got any good advice for a newby to brazing?bcwldr80MILLER BIG BLUE 300MILLER 175Miller suitcase 12 vs
Reply:You might be able to tig the hole using some copper for a filler. I have never tried tigging copper but I have seen it done and it does a very nice job.Miller DVI2Lincoln Precision Tig 225Thermodynamics Cutmaster 38Everything else needed.
Reply:yup, get your hands on some copper filler wire.  Its pretty easy to do as long as your confortable with thin material.I wonder if you can use thin gauge wire for filler?Have we all gone mad?
Reply:Originally Posted by bcwldr80...The silver solder just rolls of the original copper tubing,yet it attaches to the copper piece placed over top of the hole...
Reply:Originally Posted by denrepWith solder rolling off of the clean tube, while bonding to the patch, I wonder if the tube actually is something other than copper.
Reply:Agreed Rojo, As a test, I would scrape and try to "tin" another spot on the coil.
Reply:Thanks for the replies guys, I file the tubing to a clean copper looking shine before beginning preheat and welding.Your comment about something other than water is good because I know that there is a chemical glycol among other things that helps keep the pipes free from alkaline buildup.That could be why I got much better results soldering a seam that had no leaks with good penetration.I will also look for the silver solder flux that Rojo mentioned as well as trying a 25% silver filler rod. Sometime next week I will get to that project again.Happy hunting. Until next time.bcwldr80MILLER BIG BLUE 300MILLER 175Miller suitcase 12 vs
Reply:Easy to TIG with silicon bronze filler wire.
Reply:bcwldr80, I'm confused by the mixture of soldering and welding terminology you are using to describe what you have tried.  Solders can't normally be used to fill a hole of any size, since they rely on capillary action to be drawn into the thin gap between work surfaces.  You can't normally build up a patch with solder alone unless the hole is much smaller than 1/8".Are you using low temperature silver bearing soft solder intended for copper plumbing like "Bridgit" or "SilvaBrite" or hard "silver solder?"  They are quite different and your description sounds like low temperature solder that melts around 500 degrees F.  Such solder should work fine soldering a patch onto tube with clean materials, but since you are having difficulty getting wetting," or tinning of the surface, I agree with others that contamination may be the problem.One problem with low temperature fluxes is that if you overheat them by using too hot a torch or as you struggle to get wetting, they chemically change to dark residues that inhibit any further wetting.  Then you have to start over with the cleaning.  More heat after the brown residue forms just makes things worse.What type of torch are you using?  You can definitely soft solder with an Oxy-Acetylene torch, but it takes finesse and experience to avoid overheating the work because the flame is much hotter than necessary.  A propane torch will work fine for soft soldering most objects.For hard soldering a propane torch will sometimes provide enough heat if the object is not too large or thick so that heat is not wicked away too quickly, but a $40 MAPP torch (with the yellow bottles) will easily be hot enough for most objects.  I definitely recommend using the lowest temperature torch that will get the job done to minimize the risk of overheating.I'd suggest "easy" hard silver solder with silver brazing flux to solder on your patch.  "Easy" refers to a hard solder alloy that melts at the low end of the temperature range for hard solders.  Silver brazing flux usually looks like a white paste or dry white granular powder.  When you first heat the paste flux, it dries out to a powder stuck to the work surface.  Then, for either dry powder flux or dried-out paste flux, as temperature gets high enough the flux turns into a clear, viscous liquid which is very active in cleaning the work surface.  It is also a very useful indicator that you are approaching hard soldering temperatures in the neighborhood of 900 degrees F.Be sure that the system you are patching has an opening to the atmosphere somewhere other than at your patch so the expanding air has someplace to go other than through your joint.Have fun.awright
Reply:if the joint is not required to flex- try a phospor-copper hard solder like the plumbers use for copper AC fittings on tubing. plenty strong and not as much problem as high-silver soldersfill the hole with a piece of copper electrical wire bent into a U and tapped into the hole to almost completely fill it ( #14 is common in house wiring and a reasonable fit for that size hole) , then solder it up and file it off flush. if the tube can be tinned with the phosphor copper solder then clean up both surfaces and heat them together very gently but quickly in a small spot, play the most heat onto the heavy part, once the solder will melt then fill as you go along but be very careful to heat away from the solder direction as it will run out quickly if you over  heat it. use a small torch tip and let the pieced soak up the heat. many silver solders flow very easily but like water, they run out also. others can be more viscous like the phosphor-based ones, and with some small amount of silver in them it helps them wet up. once you have a few spots soldered then you can cool the part again and go back to fill in the others. heat control is very important. hot coppers are a good example of what used to be the method for this but they cant heat the big part - that would have been preheated by torch and then the coppers used to heat the tube up locally to fusing temp for the filler.Last edited by lucywalker; 01-07-2008 at 07:06 PM.
Reply:Just finished welding the leaks on the coil. It turns out that I used the cutting torch at hottest setting.With a 5-7 minute preheat.The reason that the brass filler didn't melt to the copper is because the 3 lbs of brass next to it sucked up the heat. I was shocked that it took that much preheat. But the result is a plugged hole and a repaired steam heat coil.It may look like a stitched up cows ***, but it does not leak.bcwldr80MILLER BIG BLUE 300MILLER 175Miller suitcase 12 vs