Dry Ice & Acetone

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Yea I know Cryo is the way to go but I would like to do some Experimenting.
Anybody willing to fess up and tell me how to do this
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I want to try it on some 5160.

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RHankins Available knives
http://albums.photopoint.com/j/AlbumList?u=205453
 
Dry Ice and Kerosene is a much less volatile misture, and less expensive, too-you can do it in a styrofoam cooler. Put the lid on and let it go until there is no more dry ice and the mixture is at room temp.

RJ
 
Hey yall,
This is a new one on me. Home spun cryogenics? How cold will the dry ice and kerosene mix get? Dry ice is something like 120 degF below zero isn't it? How much colder does it get with the kerosens mix? I have heard that to get reliable results with cryogenics that you need to take a blade under 200degF below zero. Is this correct?

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http://www.livelyknives.com
 
Proper cryo is done with liquid nitrogen because its as close as we can come to absolute zero......personally, I think you are just kidding yourself with dry ice and anything.
 
Actually, Liquid Helium is much closer to absolute zero (-273 kelvin or -454 f) but it's a heckuva lot more expensive. It's used in certain scientific applications. Liquid Nitrigen is not all that expensive.

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Glen AKA Centaur
"I'll be your Huckleberry."
- Doc Holiday
 
It's my understanding that dry ice/acetone will get you down to the -100 range. Cold enough to do something but whether it's does enough to make it worth the mess, time and effort, well you'd probably have to be the judge. As Centaur say's the nitrogen isn't expensive, it's the storage dewar that costs you. -Guy Thomas
 
Dry ice is only -110F. Even with acetone (using the heat of vaporization) you would get very little colder. I put pea size pieces of dry ice in my mouth, keep it moving from side to side, and blow CO² gas our my nose and mouth. Freaks the kids out at Holloween! But I don't swallow it. You couldn't do this with liquid nitrogen but LN² would be the way to go for cryotreatment.

Bruce Woodbury
 
I do reactions in dry ice/acetone all of the time. It gives you a pretty reliable -78 C. I don't know what temp you are looking for. However I believe that if you put a really hot piece of steel into this it won't cool quite as fast as you expect because you will probably form a vapor barrier of acetone around the knife and the heat won't conduct very well.
 
Hey Critical, if you are interested in knowing, the hot steel is not quenched in the super cold medium. Steels that contain large amounts of chromium benefit from a super cold quench from room temperatue after the blade has been hardened. This helps change most of the retained austenite into martensite. Hope that helped!-Guy Thomas
 
Tom: Sorry, you are mistaken. There are definite benefits associated with -120F, although the benefits of LN2 @-320F are more.
Even at -120, you are fully 190 degrees below RT, and, for most steels you can get into the 90+% Martensite range. LN2 will get you 99+%, and, for all practical purposes it is the ultimate treatment.
You can learn a lot about Cryogenics in the book "Cryogenics", by Bill Bryson, published by Hansen Gardner. It's about $40, and is a great practical book, written in laymen's terms.
Rememember, one of the great benefits of cryo is to compensate for non-ideal heat treatment, of which, I'd guess nearly 90% of all heat treatment performed is.
Dry ice and kerosene can do wonders for a blade that was non-optimally heat treated. For over soaked blades, for example, just putting a blade in the freezer overnight can increase the hardness by a point. I've done it, back when I was first developing my cycles for A2.



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Stay Sharp,

RJ Martin
http://www.martinsite.com
 
Bill Bryson, in his book on heat treating tool steels, recommends the kerosene and dry ice combination.

Paul Bos told me at the Blade show last year that he has stopped doing the -300 degree cryo because the improvement in transformation for the cost of seals and other problems was not enough to merit the extra hassle. He still does sub-zero cryo, but at a much higher temperature.

Don Cowles
www.cowlesknives.com
 
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