Re: [Chrysler300] replacing trunion with u-joint

[mr-320@xxxx]

lo stranger;
im very interested in the broken trunnion pin as i am in the
business of cryo-treating . ill just bet that the metallurgical fault
you found, in the broken ends of the pin, was a small, roundish nubbin
that abutted the surface just at the break. if so, what it was is an
austenitic inclusion, in the post heat treat martensitic grain structure
of the pin. had the part been cryo-treated [frozen] , the stress riser
induced by this inclusion, would not have existed, it would have been
incorporated into the martensitic grain structure of the pin, and it [in
all probability] would not have broken, because the weak spot didnt
exist any longer, it had been induced, by the cryogenic temperatures, to
complete the transition that heat treating tried to induce on the part
and was only 85-90% successful. cryo-treating brings this success % up
to 99+ . that broken trunnion pin is a perfect example of the type of
metallurgical defects that cryo-treating eliminates. it, of course, does
nothing for mechanical defects, foreign objects, folds in the metal and
pre existing cracks, only austenitic inclusions and their accompanying
stress risers are affected...

JEFF
tucson az.