Brazing copper and stainless steel help

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Hello, I have a problem.  I have a copper tube that I want to braze a hollow stainless steel part inside.The braze has to be air and water tight so that it will not leak.  Also, adding filler material from the outside cant be done as the flange has to be clear of any filler material.  My previous attempts have failed, to where they leak.  I have taken out the stainless steel part and have noticed that the brazing material is mostly on one side.(pictured is a old design but the results are the same)I constantly rotate the piece while heating up the tube with a flame.  Does anyone have any tips or suggestions on how to braze these to parts together? Would heating the inside of the hollow stainless steel part instead of the copper tube be a better idea? Any help would be appreiciatedThank you
Reply:What filler did you use, what did you apply the heat with, what is the gap between the tubes, how were surfaces prepared, any flux, intended operating condition temp range and fluids as well as function, yada yada.
Reply:We used a silver solder, we used a flame from a torch, the gap is .004" radial, yes there was flux, under pressure 100% of the time no more than 100psi and max temp of 200*F
Reply:Brazing? With solder at 200°F? hmmm..
Reply:sorry, meant silver brazing rod
Reply:Too cold.  Maybe this will help.http://www.harrisproductsgroup.com/e...Soldering.aspxMM200 w/Spoolmatic 1Syncrowave 180SDBobcat 225G Plus - LP/NGMUTT Suitcase WirefeederWC-1S/Spoolmatic 1HF-251D-1PakMaster 100XL '68 Red Face Code #6633 projectStar Jet 21-110Save Second Base!
Reply:Originally Posted by homeyjoseyWe used a silver solder, we used a flame from a torch, the gap is .004" radial, yes there was flux, under pressure 100% of the time no more than 100psi and max temp of 200*F
Reply:You may be running into a problem with differential thermal expansion coefficients. You may want to do some real brazing with silicon bronze rod or whatever people usually use, rather than solder, around the bottom and then chuck it up in a lathe to remove the filler from the flange. I think solder is fine for similar materials but this is a different situation.
Reply:You didn't mention the grade of stainless, but 304 stainless steel and copper have almost identical expansion coefficients . . . however, heating from the outside will make the copper tube hotter and it will expand away from the stainless.Dynasty 300DXSmith He/Ar gas mixerMM350PHobart Handler 120Smith LW7, MW5, AW1A
Reply:I ran across this post and figured I would throw my 2cents in. If the two pieces are fairly snug together get some brazing rod and "sweat" the two pieces together. This requires both pieces be at temperatures hot enough to melt the filler rod without heat from the torch being present when adding the filler, if both pieces are heated to the correct temp (very hot) you will see the filler pull it's self into the joint as soon as you add it.This is how HVAC hi pressure copper lines are put together (300+ psi) , if you have a large tolerance or gap that needs to be filled this will NOT work!Real welders know how to penetrate!(Equipment)Whatever can be used to beat my opponent into submission!
Reply:Then either the gap is too big or wrong filler.I have never seen silver solder used on stainless. Is this appropriate?
Reply:Originally Posted by atgI have never seen silver solder used on stainless. Is this appropriate?
Reply:Ok maybe the oxide is reforming on the stainless when you heat it, or it is the wrong flux. Silver solder seems fine according to this link: http://morebeer.com/brewingtechnique....6/palmer.html
Reply:Silver solder is commonly used for stainless and is what I would choose for this job. You do need to use a flux made for use with stainless. You can call Harris or other manufacturers and get their recommendations.JohnA few weldersA lot of hammersA whole lot of C-clamps