copper sheets- weld? braze? solder? etc.?

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I want to take a couple sheets of 12 ga. copper, cut it into strips and adhere it together to form a U shape (bottom being flat, not curved like the U is), to form like a channel.   one vertical leg will be 17", the other vertical leg 2".  The web or horizontal piece that the two legs are joined to would be lil over 6" in width. So it would be like a 6" piece of channel iron w/ one grossly tall leg and one short leg.  The prints show the legs being welded 1/8 in. from outside of web so that it is a T joint rather than a corner joint.  Assuming the filler metal needs to match color of copper, what does anyone reccomend?  Want to cut it the length of the sheet which is probally 8'. also there would be a couple butt welds to make the channel longer than the sheets     These are going to lay atop a cinder block wall w/ very little anchoring or adhesive to hold them in place.     So warpage would be a big issue.  Anyone have any experience w/ joining copper.    i was thinking of TIG.   any advice at all would be welcome.Last edited by 123weld; 04-29-2009 at 10:44 PM.
Reply:I have a couple of questions: Is this going to be decorative and is it expected to weather uniformly?Why can't a large sheet just be bent, leaving a lip where the "T" edge is on each side? Wouldn't that be easier/less expensive? What about the annealing that welding/brazing will cause?Seems to me that because of the shrinkage in the weld area, you'll need some kind of jig to hold everything well in place, followed by peening to stretch it again, in order to control the warping. I've never tried this, so might be wrong!
Reply:I have actually sheared sown small stips of the material to use as filler.   IT works some of the timeVantage 500's LN-25's, VI-400's, cobramatics, Miller migs, synch 350 LX, Powcon inverters, XMT's, 250 Ton Acurrpress 12' brake, 1/4" 10' Atlantic shear,Koikie plasma table W/ esab plasmas. marvel & hyd-mech saws, pirrana & metal muncher punches.
Reply:Thanks Old Iron, yes its outdoors and should look uniform, I'm not familiar w/ the annealing or what happens to copper after its been heated up, Its non structural-more ornamental like.   The people dont want it bent, they want it done as in the plans.   The plans don't specify what type of weld.  You mention warpage, well thats my concern also. Do you think by Brazing, there will less warpage?    You mentioned weather uniformly, whats your thoughts or suggestion about that?     Thanks to the other reply of cutting strips, sounds like that would help w/ the color match.
Reply:Very easy to braze this nice thick copper !-Use Copper Phosphate 0 (no silver content) as your filler rod (I use Aufhauser Brand).-No flux is required either.  Just make sure the copper is 'somewhat clean'.Use a fairly neutral flame with about a '0' tip (or Propylene Bottle if that's all you have..) and lightly heat the pieces of copper evenly (at the joint of course..).  You won't even need to come close to cherry red and that copper phos will wet into ANY joint with ease (closer to soldering really...).  The color match is also quite EXCELLENT.  I do LOTS of copper this way....Experiment with a few small pieces and I think you'll be pleasantly surprised at how easy it is to use.  The bond is Very Strong too...Also, don't forget that the parent metal may become VERY soft after annealing so I would suggest putting the piece in between to 'heavy pieces' of cardboard and lightly pound it with a rubber mallet.  This will harden the copper and then it won't bend at the brazed joint.  Your copper is quite thick so you may not even have to do this step.....Cheers !/Jman...
Reply:Jman's suggestion is probably as good as you'll get. Copper/phosphorus is widely used in the refrigeration business, both for new and repair. As applied, I think it usually is a bit darker colored, but that may clean up well and then look just the same color; I can't remember if I've ever tried. It will probably be great as is; they want ornamental looks, you said. Adds class and 'texture'.The low working temperature will lessen warping, the alloy will be easier and faster to apply,  and probably cheaper that TIGing.Last edited by Oldiron2; 05-01-2009 at 01:29 AM.
Reply:Thanks you two guys, I'm hoping to get some scraps of copper beggining next week to play around w/.    I may come up w/ more questions then.
Reply:Originally Posted by 123weldThanks you two guys, I'm hoping to get some scraps of copper beggining next week to play around w/.    I may come up w/ more questions then.