Is the -300 cryo treatment just hype?

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apox77

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Sep 24, 2003
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In the July 2005 issue of Tactical Knives there is an articel on page 24 in which the author (Chuck Karwan)writes that the -300 degree treatment is not needed and that -100 is sufficient.

If this were true then acetone/dry ice would be sufficient


Anyone test the two head to head?
 
When I saw this thread, I looked around to find the exact temp that was required.....but couldn't find it quickly. I may be mistaken, but I believe the temp required is around -125 to obtain any effect. Maybe I'll find it soon, and if I do I'll come back and post it....maybe someone with a better memory than I will pop up in the meant time.

Anyway, I think the acetone and dry ice thing is more hype than anything else. That mixture will only achieve about -70F, which is no better than throwing the blades in a deep freeze.
Does cryo make a difference? Speaking strictly for forged 5160 and 52100...YES! From the tests I have conducted it produces about 15% more cutting ability in 5160, and as much as 20% in 52100. These results were achieved by allowing a 10 hour soak in the liquid nitrogen.
 
I remember reading a while ago that the acetone/dry ice could get to about -110. I'll try and find that also.
 
Okay, I just searched the internet and the consensus seems to be that the acetone/dry ice slurry will achieve a -78 C. which converts to about -108 F.

So if the article is correct (that -100F is all thats needed) then the Acetone/dry ice should work.
 
I would suggest speaking to the people you buy your steel from..........
When I contacted crucible, they said a solution of dry ice and a non freezing liquid would be fine, just a longer duration would be needed as opposed to liquid nitrogen.
I've seen alot of posts for and agiants cryo..for an agiants dry ice...

I just go by what the people who make the metal tell me. they have alot more money in testing than I do
 
I've used similar 52100 blades where one has been deep cryo'd and the other has had a brief dip. I'll happily keep paying for blades that have had a deep cryo.
 
I've been involved in many discussions about -300F cryo .There is a lot of hype about it but so far no one has been able to tell me exactly what happens to the steel if anything . So the jury is still out. -100F on the other hand is significant in reducing retained austenite but it won't do much for the simple steels.
 
Generally and specifically for me deep cryo is less costly overall. One 22 mile trip and $68 for LN will cover my cryogenic needs for at least 3 to 4 months. The cost of the dewar is pretty painful but it beats 10 bucks and a 22 mile trip to buy ice each time needed. Deep cryo also requires less treatment time.

I started out doing the dry ice thing. I feel my results are better with deep cryo.

RL
 
I've used both methods, using dry ice inside a styrofoam icebox overnight, with the blade sandwiched beteen two blocks of ice. Believe it or not, there's still ice there the next day.

I have a rockwell tester, and test every blade I make after quench, and after each temper.

I do this only on stainless alloys.

I always get between one and two Rc points rise from the cryo, but can't predict the exact result, so it's necessary to adjust the second and last temper temperature to suit the actual result from the cryo.

So, as far as I'm concerned, the rise in hardness proves that the dry ice treatment is effective, but in actual use, I doubt anyone could tell any actual difference between two identical blades, one cryo'ed and the other quenched and tempered to the same Rc hardness.

I believe stainless alloys carefully <<<TRIPLE>>> tempered for 2 hrs. each time and hardness checked between the cyles is going to give you about the best you can get whether it's cryo treated or not.
 
I read that article and there is a lot of misinformation in it.

If you look at the CCT, Continuous Cooling Transformation curves, for tool steel alloys you will see a martensite start and martensite finish temperature. High alloy materials retain a lot of austenite during heat treatment. There are two ways to convert this. 1. During the tempering the steel will cycle through the martensite start range and convert austenite. 2. Freeze the material to get as close to the martensite finish temperature as you can.

The martensite start temperature for D2 is about 450 F. The Martensite finish temperature is a moving target depending on heat treat temperature and time at temperature. Under normal times and temps D2's martensite finish will be below zero and can be as low as 200-300 F below zero.

If you need complete transformation of retained austenite you may have to use lower than 100 below freezing or you will need very high tempering temperatures.

The main reason most people do not see any benefit to freezing steels and some do lies in the initial heat treating parameters.
 
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