[Bulk] Re: [Bulk] Heat treating aluminum header?

[Bill Glaze]

Karl:
It has a ball
Understand your standpoint on the technical stuff.
You are quite correct in your statements.  BTW: I used to use a 600 deg. 
steam cabinet for normalizing
and a passivationg bath.  (Neither of which belonged to me.)
Bill Glaze


Bob Kane wrote:

>Does that one use the point or the ball, I can't
>remember . . . .
>
>--- "Karl G. Mueller" <kgamueller at rogers.com> wrote:
>
>  
>
>>Bill,
>>
>>You're correct that aluminum has to be quenched,
>>usually in some type of salt bath,
>>to be annealed. In the case of a header you are
>>looking at a finished item with
>>various material thicknesses (flange). If you quench
>>an item like this you will
>>induce stresses because part of the item (thin wall
>>tubing) will cool of faster than the
>>heavier flange. I have used this method (electric
>>oven) a lot to take the T6 hardness
>>out of 6061 aluminum.
>>I don't think that the heat from the exhaust is high
>>enough to put the header in a 
>>continued annealed condition, but high enough to
>>cause some artificial aging ???
>>Vibration and more so continuous flexing of the
>>header with too much weight
>>(tuned pipe) on the end of it will cause it to break
>>eventually.
>>I did not want to get to technical in my first post,
>>just something  the average modeler
>>should be able to do. Not everybody has a Brinnell
>>Hardness Scale at home :-).
>>
>>Karl G. Mueller
>>kgamueller at rogers.com
>>
>>  ----- Original Message ----- 
>>  From: Bill Glaze 
>>  To: discussion at nsrca.org 
>>  Sent: Thursday, September 08, 2005 9:50 AM
>>  Subject: [Bulk] Re: [Bulk] Heat treating aluminum
>>header?
>>
>>
>>  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
>>
>>      ----- Original Message ----- 
>>      From: JonLowe at aol.com 
>>      To: 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
>>
>>    
>>
>
>
>Bob Kane
>getterflash at yahoo.com
>
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