"John R. Carroll" wrote in message
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"Ed Huntress" wrote in message
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"Buerste" wrote in message
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snip

But the poster thinks that cyro treating is going to make his piece
harder, sharper and tougher, ain't gonna' happen like he thinks. I'll
refer to my bud George Fisher of "Ion-vacuum Technologies"
http://www.ivactech.com/ George knows cutting tools and materials and is
probably one of the top 10 physicists on the planet. We've discussed
cyro treating many times and I relayed his opinion. It seems you'll get
a different opinion from people that do cyro for a living...kind of like
global warming.

The effects of cryogenic treatment aren't a matter of opinion, Tom.
There's been extensive testing over the years in independent labs. This
was fully settled by the time I was covering materials for _American
Machinist_, back in the late '70s.

In cases where conversion from austenite to martensite is not complete,
cryo treatment can complete the conversion. This eliminates the
room-temperature austenite phase that paradoxically keeps the piece from
achieving its full potential hardness, and also contributes to
brittleness or other weakness through a mechanism I don't remember. (Hey,
it's been 30 years.)


Hydrogen embrittlement?

I don't remember it being that. It's something about the way that austenite
and martensite co-exist in steel at room temperature. The summary is, they
don't do it very well.



But the effects are slight. They can pay off in some kinds of press
tooling, which is where the method was being applied in those days.
Adding small margins of performance can add tens of thousands of hits to
the life of a blanking tool, for example.

Another benefit is grain structure orientation Ed.
That's principally why I do it. The grain tends to reorient along the
shape of the part.
That can be extremely useful in welded Stainless Steel assemblies, for
example.

That's interesting, and curious. I can't imagine how that works but maybe
I'll look it up sometime. Given the state of publishing about manufacturing,
there isn't likely to be a reason for me to do so. d8-)

--
Ed Huntress