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This is getting to be a rather absorbing thread; at least for me. I
had always been taught that aluminum anneals like brass and copper;
that is, opposite to steel. I had been taught that to anneal aluminum,
(or brass, as in cartridge cases, or copper, as in cold worked bullet
jackets) that one heats the material, then chills it rapidly. In fact,
even with lead, which most people would think is, well, just lead, that
lead in its pure state, or alloyed with the common metals, (tin,
antimony, others) can be hardened. In fact, by heating lead bullets in
an oven to just below deformation temperatures, (just below where the
bullets would begin to "slump") for an hour, then rapidly immersing
them in cold water, I have been able to raise the Brinnell of the
bullets from 9-10 to over 20.<br>
What I am wondering is if the aluminum headers are being hardened to
brittleness by "work hardening" caused by minute vibrations, repeated
thousands of times.<br>
Because the applied exhaust heat would, it seems, tend to put the
aluminum in a continual annealing condition.<br>
I was in the aluminum window manufacturing business for many years. We
used several hardnesses of aluminum, and several different hardening
processes; heat treating, artificial aging, artificial hardening, etc.<br>
Of course, when flying for United Airlines, in severe turbulence, I
found myself hoping that the wing spars hadn't been work hardened to
the brittleness stage!<br>
Sorry for the long posting, but, as I said, it is an extremely
interesting thread.<br>
<br>
Bill Glaze<br>
<br>
Karl G. Mueller wrote:<br>
<blockquote cite="mid004701c5b471$5b084560$04000005@cr398119a"
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<div>Jon,</div>
<div> </div>
<div>The problem with the aluminum being heated and cooled every time</div>
<div>you run the engine acts like an artificial aging (hardening). In
time the </div>
<div>material will get very brittle and therefore break very easy.
Here is a little</div>
<div>trick you can try that I know works: If you have a self cleaning
electric oven</div>
<div>at home, put the header in the oven run the cleaning cycle. Do
that at night</div>
<div>before you go to bed and the next morning you header will be
annealed.</div>
<div>It has to cool of slowly.This is the opposite process of
hardening. This makes</div>
<div>the aluminum more flexible and less prone to breakage.</div>
<div> </div>
<div>Karl G. Mueller<br>
<a href="mailto:kgamueller@rogers.com">kgamueller@rogers.com</a><br>
</div>
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<div
style="font-family: arial; font-style: normal; font-variant: normal; font-weight: normal; font-size: 10pt; line-height: normal; font-size-adjust: none; font-stretch: normal;">-----
Original Message ----- </div>
<div
style="background: rgb(228, 228, 228) none repeat scroll 0%; -moz-background-clip: initial; -moz-background-origin: initial; -moz-background-inline-policy: initial; font-family: arial; font-style: normal; font-variant: normal; font-weight: normal; font-size: 10pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"><b>From:</b>
<a title="JonLowe@aol.com" href="mailto:JonLowe@aol.com">JonLowe@aol.com</a>
</div>
<div
style="font-family: arial; font-style: normal; font-variant: normal; font-weight: normal; font-size: 10pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"><b>To:</b>
<a title="discussion@nsrca.org" href="mailto:discussion@nsrca.org">discussion@nsrca.org</a>
</div>
<div
style="font-family: arial; font-style: normal; font-variant: normal; font-weight: normal; font-size: 10pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"><b>Sent:</b>
Wednesday, September 07, 2005 8:39 PM</div>
<div
style="font-family: arial; font-style: normal; font-variant: normal; font-weight: normal; font-size: 10pt; line-height: normal; font-size-adjust: none; font-stretch: normal;"><b>Subject:</b>
[Bulk] Heat treating aluminum header?</div>
<div><br>
</div>
<div>After many many flights, I had an aluminum header break for my
OS 1.60. I had it welded up by a very good welder, but the header
broke again after one flight in an area removed from the weld, but
close enough that it would have gotten pretty hot. I suspect that the
heat treat of the header got changed. Any ideas on how to try to heat
treat a second pipe that has benn welded to try to at least get more
than one flight? I've odered a new header, but it is not here yet.</div>
<div> </div>
<div>Thanks</div>
<div> </div>
<div><font ptsize="10" size="2">Jon Lowe<br>
</font></div>
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