[Bulk] Heat treating aluminum header?

Bill Glaze billglaze at triad.rr.com
Thu Sep 8 05:50:58 AKDT 2005


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.
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.
Because the applied exhaust heat would, it seems, tend to put the 
aluminum in a continual annealing condition.
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.
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!
Sorry for the long posting, but, as I said, it is an extremely 
interesting thread.

Bill Glaze

Karl G. Mueller wrote:

> Jon,
>  
> The problem with the aluminum being heated and cooled every time
> you run the engine acts like an artificial aging (hardening). In time the
> material will get very brittle and therefore break very easy. Here is 
> a little
> trick you can try that I know works: If you have a self cleaning 
> electric oven
> at home, put the header in the oven run the cleaning cycle. Do that at 
> night
> before you go to bed and the next morning you header will be annealed.
> It has to cool of slowly.This is the opposite process of hardening. 
> This makes
> the aluminum more flexible and less prone to breakage.
>  
> Karl G. Mueller
> kgamueller at rogers.com <mailto:kgamueller at rogers.com>
>
>     ----- Original Message -----
>     From: JonLowe at aol.com <mailto:JonLowe at aol.com>
>     To: discussion at nsrca.org <mailto:discussion at nsrca.org>
>     Sent: Wednesday, September 07, 2005 8:39 PM
>     Subject: [Bulk] Heat treating aluminum header?
>
>     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.
>      
>     Thanks
>      
>     Jon Lowe
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.f3a.us/pipermail/nsrca-discussion/attachments/20050908/38e58391/attachment.html


More information about the NSRCA-discussion mailing list