FWIW; I did some tests on JB weld to get an idea of how well it holds,
and how it does at elevated temp. I was impressed with it's strength at
room temperature, and disappointed with its strength at 250F.

 I was considering its use on cooling system components; specifically on
a thin walled aluminum surge tank (fire extinguisher bottle) where
welding is a bit dicey.  I was surprised that it says on the package
that it is good to 600F. This was pretty much qualitative, although I
did bond roughly 1 sq. in. on flat stock and made a rough estimate of
force required to break.  I prepared samples of both aluminum and SS,
sanded with 120 grit, cleaned with acetone.  Cured for 18 hours at room
temp, then baked a couple of hours at 180F.

Stressed at room temp to maybe a few hundred psi in tension and more in
shear.  It held fine, pretty impressive.  Didn't go further because I
had only one sample, and wanted to test it at temperature.  Heated it to
250F, then applied some force again.  Both samples broke before I
expected.  Still some strength, but probably less than 100 psi. tension;
more in shear.

My conclusion was that it can be used a cooling system temps for sealing
and filling, and maybe some shear loads, but not reliably where you
expect tensile loading.  I don't think I'd use it to bond a wiggin's
style coupling to the pump or lines as was discussed some time ago.

 Mostly all this just confirmed what I already had guessed.  I have no
idea what they mean saying it's good to 600F.  I guess it means it stays
where you put it; just don't expect it to carry any loads.

Has anybody tried the A-lum-rite brazing?

Al

 
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