On Sun, 22 Jan 2006 10:34:22 GMT, Ernie Leimkuhler
wrote:


Allstate also sells aluminum brazing supplies.
They call it Allstate #31

Good stuff for thin metal, be sure to get the #31 flux as well. It
doe not work well (for me) on metal over .062" for some reason.
Allstate #31 was developed for HVAC work, joining aluminum tubing in
refrigeration systems. It works really well for that. I first
saw it demonstrated at an ASHRAE show when it was first introduced. I
was amazed.

Tinmantech also offers a similar brazing material, Aerobraze, with
companion flux.

I've had varying reports from others on these two materials: some say
one works for them while the other doesn't, and conversely. I don't
know why. I like them both on thin metal. The Allstate #31 is way
lots cheaper, available from Grainger.

The difference in temperature between either of them and welding is
less than 100 degrees F. That's a big difference on thin metal,
but I find it as easy or easier to weld as to braze on material .050"
and thicker. Neither of these materials work well for butt joints;
they're better for fillet or lap joints as one might design for
brazing. Butt joints and outside corner joints are best done by
welding.

I guess they're really different processes. I can cut a preform out
of either Allstate #31 or Aerobraze, set it in place with appropriate
flux, heat until it wets and flows resulting in a joint that looks
just like a silverbrazed joint in brass or steel. Welding aluminum
is, well, more like welding, melt and dab while controlling a puddle.