I got your "cryo" treatment right here...

[urq]

> >But seriously...what exactly -is- it that these cryo-treatment companies
> >  do that's so special?
>
> Ok, I answered my own question.
>
> Apparently, they lower the part to -300 degrees or so over 8 hours,
> let it sit for a while(10 hours or so), and warm it up slowly, then
> heat it up to 300 degrees, because the freezing makes it very
> brittle...
>
... many times when a part is cast as it is solidifying in the mold, points
of internal stress are created.  Internal stress is one of the things that
can serve as a starting point for cracks ... warpage can also be attributed
to internal stress.  What happens when a part is cryo treated is that it
allows internal stresses to be worked out as the crystalline structure
reforms.  The temperature changes are highly controlled to try to maintain a
consistent temperature within the part being treated ... temperature
differences in the part can create internal stresses as well; so yeah, if
your cryo guy simply drops your part into a cooler and pours liquid nitrogen
in it is not likely to solve any problems.  I hear people say that
cryogenically treated brake rotors last longer, and I know that a good
percentage of the rifles used for competition are cryogenically treated.

In my case the reasoning is that it is pretty well known that Audi 5-cyl
EM's are prone to cracking.  Cryo treatment of an EM really isn't that
expensive, and if I can buy some level of insurance that I won't have to
deal with the EM again afterwards to me it is worthwhile.  The strange thing
is that there is some chance you will need to have the mounting surface of
the EM re-planarized afterward ... but if you think about it that is the
same warpage you would have gotten thanks to the annealing that occurs from
the heating the part gets from normal use.  If you are interested it is
pretty easy to do some research on the web ... from that you can draw your
own conclusions ...

Steve Buchholz
San Jose, CA (USA)