Cryo

Cliff Stamp said:
The problem with liquid N2 is that it is actually a very poor coolant from a speed point of view. You can actually put your hand right in it and take it
back out with no harm. I used to do this to demonstrate properties of conduction and barriers all the time in labs. Now however there are too many restrictions
on such "demonstrations". Of course if you hesitate during this process then you become handicapable fairly quickly.
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I’m calling BS on this, any lab that would let someone do this in the last 25 years would quickly no longer be a lab. Please anyone reading this don’t be stupid and try sticking your hand in LN.
 
I'm not saying people don't play with it and do stupid things. I’ve personally used it to clean concrete. I'm saying no lab indorses doing so or would allow it.
 
True enough. That floor cleaning bit surprised me, I would think it could crack the linoleum while walking on it, but it was mentioned several times. Seems like the concrete would have to be dry and without lots of cracks too. I don't think that would work down here. The water table is around your ankles, our concrete slabs are pretty much floating. I use to run a 42K lb. forklift, and gallons of water would come up between the expansion joints when moving through the yard.
 
yeah, some of those things on that page sound like alot of BS. I've only used it to clean concrete and that was as a last resort after everything else. I thought it was pretty harsh, but it did work very well. I wouldn't try it on wood or linoleum, and that is the first I've ever heard of it used on those types of floors.
 
Well, Cliff, I don't know what "kind" of LN2 you get, but, mine makes stuff cold. Really cold. Obscenely cold....And quickly, too.

So cold that when I remove my blades, 30 minutes later they are still covered with ice crystals from moisture in the air.

And, the stuff I get makes a measureable, observable difference in the physical properties of the blades I put in it.
 
rj martin said:
Well, Cliff, I don't know what "kind" of LN2 you get, but, mine makes stuff cold. Really cold. Obscenely cold....And quickly, too.

So cold that when I remove my blades, 30 minutes later they are still covered with ice crystals from moisture in the air.

And, the stuff I get makes a measureable, observable difference in the physical properties of the blades I put in it.
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I agree, how slow it might be is not really an issue, liquid nitrogen is an industry standard because it reduces retained austenite, which has been shown in many tests. What exactly are we worried about?
 
So can we take our knives outside when it is -17 below zero? Will it turn it to a brittle, useless piece of junk? Or will it help?
 
magneto said:
So can we take our knives outside when it is -17 below zero? Will it turn it to a brittle, useless piece of junk? Or will it help?
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If you convert any retained austenite you'd want to re-temper the blade.
 
So how can a layman know whether or not that he has converted any retained austenite?
 
The bad way. :( Untempered martensite can be extremely unforgiving and can even crack without being used.
 
yeah, but if there's enough untempered martensite to cause problems, wouldn't you first need enough retained austenite to make for a pretty crappy blade to begin with?
 
Yes, but the solution is usually to buy a new knife and not freeze the deliquent until its blade explodes. That's sort of vengeful.
 
The bad way. Untempered martensite can be extremely unforgiving and can even crack without being used.
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That would absolutely suck! So we can't take our knives out to play when it is below 0?
 
"I told you to get rid of that burr! You remember what happened to that underhardened Cliphanger, don't you? Either you cooperate with the Spyderco ultrafine, or it's the freezer for you!"

hmm, intimidation as a honing step, new meaning to scary sharp
 
We have two types of Cryo treatment.

1. LN at approx. -100 to -120 degrees F, this has been used for many years in the bearing industry for retained Austenite transformation to Martensite. This is normally done in an insulated box with slow lowering of temp., not a dunk in dry ice and acetone or other thermal shock treatments.

2. Deep Cryo at -300 degrees F, this is where the mystery transformations happen. Precision target rifle barrels will show 3x life before accuracy falls off, racing car engine parts last much longer, brass musical instruments change sound, razor blades last significantly longer, womens nyloy stockings are much tougher and resist tearing.

This process is also not a dunk it in the LN,,,,it is a 8-12 hours slow reduction in temp,,,,hold at -300F and a slow rise to room temp. The total cycle is 24 to 36 hours. Heat treated steels are then raised to a tempering temperature similar to the original heat treatment.

Many idividuals continue to debunk the -300F cryo however, the main research testing published is from the Soviet Union days and is not generally available to the public.

Try the Cryo and test it for yourself,,,,do not read papers and quote others opinions or theory. My rifle barrels of 416 stainless and 4140 steel showed a greatly increased life compared to factory production, my deep cryo treated woodworking plane blades (A2 steel) will stay sharper much longer than A2 without deep cryo.

Regards.
FK
 
I haven't seen people flat out saying cryo doesn't work (but I don't get out much) but what I saw in that paper was that cryo will get you more martensite and carbides. Instead of making knives both stronger and tougher, which I guess was the general claim for cryo, this makes it stronger and more wear resistant, but getting stronger means losing toughness. Though I'm not really sure on that, as I don't really understand how much carbon is ending up in those dark carbides, and how that's affecting hardness.

There's also the notion that if you do you prior thermal cycles correctly, you wont have gobs of austenite that need sub-zero temps to convert to martensite. Seems cryo is fine, just need to use it when appropriate for the steel and job.
 
hardheart said:
I would think it could crack the linoleum while walking on it...
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It is a really poor coolant, you can just poor it right over your hand and it runs off with no effect. Try it with ice cold water and it makes much more of a difference. Liquid nitrogen just has a lower temperature, but it is fairly poor at getting there. That is in one of the basic therm labs where you can study the amount of heat transfer in emersions at different liquids and liquid N2 is one of the worst on a time basis.

rj martin said:
Well, Cliff, I don't know what "kind" of LN2 you get ...
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I used it extensively for years, it was how I developed the very high pressures needed to study stellar gas compositions/interactions. I went though about 200 L (yeah, liters) of it every 2-3 days. We made it locally alongwith liquid He, which actually needs to be surrounded by liquid N2 at all times, liquid He is MUCH colder. We also made liquid O2 which is a nice blue color, but is insanely dangerous to work with because it is so violently oxidizating.

magneto said:
So can we take our knives outside when it is -17 below zero? Will it turn it to a brittle, useless piece of junk? Or will it help?
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Your biggest problem is likely the embrittlement due to the fact that steels get brittle when it is cold simply because of the fact it is cold.


hardheart said:
I don't really understand how much carbon is ending up in those dark carbides, and how that's affecting hardness.
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Carbides precipitation tends to cause embrittlement by loading along grain boundries which is the main reason for the 500F and 950 F embrittlement regions seen in steels for example.

-Cliff
 
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