"copper" brazing

[JCKelly]

Haven't used it myself, just watched AC guy braze copper fittings together yesterday. Filler looks like a light copper, so ought to look good on iron hardware that might have been copper brazed originally. But this stuff melts some 500F or so lower than does pure copper metal. High phosphorus, when used on copper needs no flux. That was the first time I have seen fluxless torch brazing.
However, for use with brass or iron/steel one must use a braze flux, such as Harris Products "Stayfil" 
This copper-colored filler is nominal 87.9% copper, 6.1% phosphorus (the deoxidizer when brazing copper) and 6% silver. AWS spec is BCu-P-3. Solidus 1190F (where it just gets slushy) and liquidus 1465F (where it is completely liquid. Actual braze temperature should, I believe, be somewhere above 1465F. Recommended joint clearance 0.003 to 0.006". I watched the guy torch braze, nothing seemed to glow. The only scary part was he had no protective goggles on. What the heck, he had two of 'em . . . I did politely mention eyeball stuff when he was finished.
Anyway, it is a so-called "silver solder"  that almost matches copper's color. If anyone cares. Look under www.harrisproductsgroup.com, assorted video at www.infernobyharris.com

[LRB]

  Good info to know JC. Thanks for passing it on.

[docone]

When I first got into silver soldering, I used that stuff.
For doing silver work, it is miserable. The self flux makes a dark, hard scale. The resulting joint was much harder than the surrounding silver.
It definately has its limits.
I got it as it was cheap and I thought I could learn on it. I went to silver wire solder, and went from there.
That is just me, I am sure it has its purposes. I just never found them for silver work.

[David R. Pennington]

silver solder/brazing has been the industry standard for years in AC & refrigeration for joining copper tube and fittings. I use a 15% silver content type although it has become very expensive lately. When joining two like metals, ie copper to copper no flux is required but must be used if joining dissimilar metals , ie copper to brass or copper to steel. The flux does create a glass hard scale that is very difficult to remove. Every one I've ever trained burns holes in the tubing on their first try.