DEEP CRYOGENIC TEMPERING (-305F) vs CRYO TEMPERING

pahl

pahl

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Feb 23, 2002
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I'm looking at a Fillet Knife Kit and you can get it with two differant types of tempering.

What is the differance between the two?

Thanks
pahl


Edit: to repair link
 
I cryo with dry ice - about -100 F.. I place the small cooler of dry ice in the refridgerater to help preserve its life expectancy and if I could I would place it in the freezer. I get about 2 1/2 days of cryo that way. I do not know if that is as good as 8 to 12 hours at -300 F.. It is suggested, I have read, to dry ice cryo as long as the dry ice will last. If I could get 3 days out of it I would leave the blade in it for 3 days (as long as there is still ice).

Roger
 
Steels with significant amounts of chromium in them (5160, 52100, 440C, ATS-34. etc.) benefit from time spent at ultra low temperatures after they have been hardened and at some point in the tempering process. This process essentially transforms the vast majority of the retained austenite into untempered martensite and can add several points of hardness and toughness to a blade. The -300 degree F temps are achieved using liquid nitrogen. There seems to be some question whether the temps around -100 degrees F achieved using dry ice and acetone will make a lasting difference in a blade, but they certainly don't hurt and many people report increased blade performance using this method.
 
For $4 I would get the cryo treated blade. TKS offers a cryo treat as part of their heat treating service, looks like they offer to do the same to kit blades.
I had 2 ATS34 hunters heat treated and cryo treated by TKS and they really did a good job. They take a wicked edge and hold it longer than some other ATS34 knives I've had. I don't know if the cryo made the difference but I'd cough up the $4 again.

Wanted to add that the regular blade is fully heat treated and tempered, just doesn't get the cryo treatment. It would still be a good blade.
 
For four bucks, the cryo is well worth it. There's no way I'd have TKS heat treat a knife and not get the cryo. I've always had good luck with them too. Just my 2c.

Dave
 
Has anybody treated the popular Carbon steels(52100, 5160, 1095, 1084 and so on) to -120 degrees and then a seperate blade of the same steel to -300 degrees and noted any significant gain or difference in overall performance level?
I ask because I'm moving more of my knifemaking to straight Carbon steel to satisfy my "need" for sole authorship of my knives. Dry ice is good, but if liquid Nitrogen is much better, it's time for me to start saving for a Dewar.
Any info in this regard is gratefully appreciated.:D

BTW, interesting thread Pahl.:)
 
In my experience,if cryo makes a big difference your heat treat or forging or thermal cycles are a little off center for the steel you are using. When cryo does not improve performance, you are probably doing everything else right. Again this experience is from working with 5160 and more extensively with 52100. Some damascus I made responded well to cryo, but I feel that should I go back and try some other methods I could achieve the same or better performance without cryo.
 
Hallo,
Doing some experimenting with cryo treatments. Wondering about the slow oil qunech and the formation of banite. My experience is leading me to believe that cryo in Liquid Nitro has an adverse affect on 52100. Have a refference in a metallurgy book that mentions not going below -130....Anybody have any thoughts?

shane
 
I see that some fellows are discussing 5160 and 52100 and at the same time discussing TKS and cryoing. About a month ago I was advised by TKS that they do not heat treat/temper carbon steel blades. They referred to an individual who does all of theirs.
 
The studies that were named un this thread seem to be directed toward wear resistance. Still wondering if anybody has any info re: slow quench, bainite and cryo...

shane
 
We need Paul Bos to jump in here.........he uses liquid nitrogen (dry ice-you are just kidding yourself!!)

Soaks them overnite for the best results.
 
Gentlemen: Here it is, plain and simple:
The more highly alloyed the steel, the more benefit from cryo. THis is because the higher the alloy content, the lower the Mf (Martensite Finish)temp. The colder you go, the more transformation you get. LN2 is capable of producing over 99% transformation in any knife steel that was properly heat treated to begin with. As to cooling rate, the "slow down", soak and "slow-up" cycles are to prevent thermal shock from uneven cooling in thicker parts, like cylinder blocks, etc.
Being thin, knife blades can generally be dunked right in with no ill effects, since they cool rapidly through their thickness.
A snap temper, or a full temper prior to cryo produces smaller grain size and reduces the thermal stress caused by the LN2 treatment.
Double tempering after cryo is the best. A single temper is a necessity.
 
My experiments are providing contrary data. I am experiencing brittleness in 52100 blades which were triple hardened in Texaco Type A.Then Tempered at 375F twice, then Liquid Nitrogen quench for four hours, then return to room temp in vermiculite. The tempered again at 375F. Blades failed brass rod flex...Required additonal tempering at 400 and 425...one hour each then return to room temp. Cut well, but failed the flex test.
Have referencre in Metallurgy for Engineers that claims Bainite is adversely affected by extreme cold in ranges below 130F.
Does anybody have any like experiences?
shane
 
Shane, your test results are interesting and seem to fly in the face of performance tests made by others.

You keep referring to bainite when you are talking about the triple quenched 52100 blades. I'm not sure how you could have any bainite structures in a steel hardened in this manner. Bainite forms when austenite is quenched to around 900 degrees (if I'm not mistaken) and held at that temp for an extended time (I'm thinking over 12 hours).

Using the type quench you mentioned (assuming a differential hardening) the blade should be composed of fine pearlite and martensite. I don't know what could be causing the extreme brittleness however seeing as you are tempering again after the LN2 treatment. Could your tempering oven be way off?
 
Not sure either...just looking for some information....Have had really great results with 52100...until I went cryo then everything went south.

shane
 
I don't think Shane would be getting any bainite either, and certainly not at the cutting edge. 900 degrees F might in some steels give you upper bainite, but lower bainite is usually preferred in blades. It is closer in structure to martensite and is formed by holding the steel just above Mf (martensite finish) temperature for an extended period of time. Time and temp. vary with individual steels, but for 52100 you might try holding at 500 degrees for several hours (too little time can give you incomplete transformation to bainite, but there does not seem to be any detrimental effect to leaving a piece in the austempering medium for an entire day or more).

John
 
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