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

[Bob Kane]

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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