How many steels need the cryo/dry ice phase of the heat treat process?

Claims of significant improvements in a knife edge from full cryo have always been suspect. There is no doubt that freezing a complex steel to complete the quench and reduce RA creates noticeable improvements. However, noticeable improvements from a cryo process have never equated into any observable improvement in a blade's performance in my own testing. I'm sure that things like disk brakes where measurable improvements have been observed are legitimate. But the wear mechanisms of a blade are quite different and the eta carbides and possible improvement of imperfections in the lattice have never translated into noticeable improvements. If there is an improvement in edge retention it won't be on the order of 400%. Perhaps something like 10%, which would be small enough that it would be difficult to notice in real use testing.

I'm not say the effect isn't there. I'm just saying that I have looked for it and have never seen it.
 
elementfe said:
Two: Do any of the kool kids use 440c anymore? CPM 154 is better, but not dramatically better- is it enough better that 440c is obsolete?
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A few cranky old guys (:D) still use 440C, but they're very picky about who they buy it from. Some of them are using up stock they bought a ton of twenty years ago. In recent years the quality of what some folks are calling 440C has fallen dramatically, the last couple feet I bought had a nasty "orange peel" look to them no matter how I tried to finish them. If you bead-blast or coat it, it doesn't really seem to matter, but what's the point of using a high-chrome steel if you can't get a decent polish on it?

The steel still performs pretty well, but with CPM-154 and the Carpenter steels (CTS-XHP in particular) being so consistant, readily available and performing noticeably better, I don't see any reason not to spend a few dollars more per blade and skip the 440C.

As for the 400-500% increase in wear-resistance from cryo, if I'm reading the posts correctly they're saying an increase from un-HT'ed steel. If that's right then the 500% number doesn't mean anything unless we also have the references between annealed and just quenched and tempered. :confused:
 
"As for the 400-500% increase in wear-resistance from cryo, if I'm reading the posts correctly they're saying an increase from un-HT'ed steel. If that's right then the 500% number doesn't mean anything unless we also have the references between annealed and just quenched and tempered. "

I don't know. One part of Lindes web paper gives a table with the data I cited on it. Another part of the paper shows tempering as the last step in the process of heat treatment. But they don't link the 2.

Another paper , Cryogenic Quenching of Steel Revisited, Zbigniew Zurecki, indicates that hardness and wear resistance increasees along with HRC for A2 steel but at a cost of the steel chipping easier.
 
mete said:
"wear resistance increase by 400% " ?? I'd like to see the details of that .Did Linde do it or one of the cryo companies ?
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Linde markets and supplies cryogenic liquids and processing equipment, and has business partnerships with several cyrogenics companies. They're partners with Controlled Thermal Processing, for example (Linde is a subsidary of Air Liquide):

http://www.metal-wear.com/air liquide and cryo.html
 
Frank Niro said:
It seems that all stainless steels benefit from a true cryo treatment. I've had a few makers tell me they just throw their blades into a deep freeze for a few days and it does as good a job. I don't believe that. Frank
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Were these Knife Makers that told you this reputable names in the business for years ie: Darrel Ralph, Kirby Lambert etc or were they hobby knife makers? That's detail that would tell me whether to believe it or not.
 
Welcome P.C.K. I see this is your first post after joining last year.
As Adam pointed out, this is a very old thread. When doing searches, look at the posting dates before replying. Posting on old threads is called Necroposting. It is frowned upon.

Secondly, you question the authority of a statement made six years ago by Frank Nero. Frank is a well known maker and holds his own with any of the big boys. His advice is well received and greatly appreciated in Shop Talk.

In support of Franks comment, placing a blade in a freezer will not get the same results as cryo or sub-zero treatment. I know there are a few people who say it will, like Ed Fowler, but those folks are not metallurgists. Here in Shop Talk we have several metallurgists and they all say a freezer will not get the results desired.
It all has to do with the Mf of the steel. There are several lengthy threads on this subject, and IIRC, some info in the stickies about it. Some searches on Dry Ice vs Cryo and similar topics will give you a lot to read and learn.
 
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