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<DIV><FONT size=2>Bill,</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>You're correct that aluminum has to be quenched, usually in
some type of salt bath,</FONT></DIV>
<DIV><FONT size=2>to be annealed. In the case of a header you are looking
at a finished item with</FONT></DIV>
<DIV><FONT size=2>various material thicknesses (flange). If you quench an item
like this you will</FONT></DIV>
<DIV><FONT size=2>induce stresses because part of the item (thin wall
tubing) will cool of faster than the</FONT></DIV>
<DIV><FONT size=2>heavier flange. I have used this method (electric oven) a
lot to take the T6 hardness</FONT></DIV>
<DIV><FONT size=2>out of 6061 aluminum.</FONT></DIV>
<DIV><FONT size=2>I don't think that the heat from the exhaust is high enough to
put the header in a </FONT></DIV>
<DIV><FONT size=2>continued annealed condition, but high enough to cause some
artificial aging ???</FONT></DIV>
<DIV><FONT size=2>Vibration and more so continuous flexing of the header with
too much weight</FONT></DIV>
<DIV><FONT size=2>(tuned pipe) on the end of it will cause it to break
eventually.</FONT></DIV>
<DIV><FONT size=2>I did not want to get to technical in my first post, just
something the average modeler</FONT></DIV>
<DIV><FONT size=2>should be able to do. Not everybody has a Brinnell Hardness
Scale at home :-).</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>Karl G. Mueller<BR><A
href="mailto:kgamueller@rogers.com">kgamueller@rogers.com</A><BR></FONT></DIV>
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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=billglaze@triad.rr.com href="mailto:billglaze@triad.rr.com">Bill
Glaze</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=discussion@nsrca.org
href="mailto:discussion@nsrca.org">discussion@nsrca.org</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Thursday, September 08, 2005 9:50
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> [Bulk] Re: [Bulk] Heat treating
aluminum header?</DIV>
<DIV><BR></DIV>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>
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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: 10pt arial; font-size-adjust: none; font-stretch: normal">-----
Original Message ----- </DIV>
<DIV
style="BACKGROUND: rgb(228,228,228) 0% 50%; FONT: 10pt arial; font-size-adjust: none; font-stretch: normal; moz-background-clip: initial; moz-background-origin: initial; moz-background-inline-policy: initial"><B>From:</B>
<A title=JonLowe@aol.com href="mailto:JonLowe@aol.com">JonLowe@aol.com</A>
</DIV>
<DIV
style="FONT: 10pt arial; 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: 10pt arial; font-size-adjust: none; font-stretch: normal"><B>Sent:</B>
Wednesday, September 07, 2005 8:39 PM</DIV>
<DIV
style="FONT: 10pt arial; 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 size=2 ptsize="10">Jon
Lowe<BR></FONT></DIV></BLOCKQUOTE></BLOCKQUOTE></BLOCKQUOTE></BODY></HTML>