<Misc> re: cryogenic" treatments

[Knute Ream <knute@xxxxxxxxx>]

"Mark Dean" <osterbri@domain.elided> wrote:
>
>Does anyone have any FACTS regarding this "cryogenic" treatment?  What is
>the purpose of the treatment, what is the theory behind it, and is there
>any actual proof that it works (not anecdotes).  It sounds a lot like slick
>50 / duralube and other snake-oil products.

Well, by the time my response hits the digest, there will probably be half
a dozen equally or more authoritative posts, but here goes!

My exposure to cryogenic treatment is job-related; I manage a precision
metal fabrication facility.  Similar to heat treating, the basic purpose of
the cryo process is to relieve internal stresses and effectively increase
the working life of the item being treated.  Cryo apparently has a number
of advantages over heat treating (cost is not one of them), in part related
to the behavior of crystalline structures as they freeze; things tend to
straighten out a bit in the structure.  I have no personal experience with
cryogenically treated rotors, but I can attest that cryogenically treated
punch tooling doesn't require sharpening as frequently, and the overall
lifespan of the tool can double or triple.  It should be noted that proper
cryo treatment is much more than simply freezing something and warming it
back up; the rate of cooling, the target temperature, the time held at the
target temperature, and the gradual rate of warming back to room
temperature will all affect the outcome.  If heated or cooled too quickly,
it can ruin the tooling or cause cracking.  (I guess I'm trying to suggest
that you cannot cryo-treat your rotors simply by pouring liquid helium on
them...)

Since warpage appears to be the primary cause of death for BMW rotors,
anything that relieves internal stresses is a very good thing.

Just my .02 cents...

- -Knute

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