Cryogenic(sp) treatment

L

LarryLuana

Joined
Nov 16, 1998
Messages
647
Now sure on spelling but would like to know about this treatment,and how much difference it makes to a blade when done to it.
For instance on 154Cm does it increase edge retension besides making the blade harder from what I understand.
I have a Cutter's Brend, and Tom(Cutter's) says the blades in 154CM are done this way to enhance the performance of the blade.
Any info would be gladly appreciated.
Thanks.

Larry
 
In tool steels, cryogenic treating can improve abrasion resistance by as much as 400%. This can vary from steel to steel though. Cryogenic treating makes a more complete conversion from austenite to martensite. The cryogenic process is more of an extension of the heat treating process. In otherwords, cryogenic treating shouldn't be a band aid for sloppy heat treat practices. I hope this helps.
Luke
 
Thanks for the info Luke.
Still wonder if it makes for a better blade or not if it is done on some of the better blades/steels of higher end knives in comparison to lower end knives. In other words is it more of a selling tactic or is it a worth while treatment which takes extra time? In another does it really make that much difference in the performance of a blade?
Thanks.

Larry
 
First thing: I think there is a kind of a big wave around cryo.

A properly heat - treated steel will be best without cryo.

Look at Bob Doziers forum, there was this question discussed before. Bob has a certain opinion on this. www.dozierknives.com

Second thing: For the industry it might make sense to go for cryo. Because if you are heat treating hundreds of blades, it might be hard to be as exactly as if you are working on one or a couple.

The only sense is, as mentioned above, to change remaining austenite (after hardening) into martensit. The better you temper after hardening, the less you need cryo. Because the first tempering changes this remained austenite into martensit, which has to be tempered again. That´s the reason why there are two temperings in minimum.

To your question: I find it hard to say if "WE DO CRYO" is a sign of quality or of bad heat treatment. On Spyderco i would say, it is the first. But there are others of whom i would expect the second.

BTW Benchmade freezes its blades aswell but does not make such a wave on it.

Hope this helps.
 
Blop!

Thanks for the info.
From what little I have read on this, and you both have said I understand more about what this treatment does, and way I understand it now gives more consistantsy(sp) in the heat treatment over the total of the blades being heat treated, and makes sure they are kept within the range of RC, etc. for better blade performance.
Again thanks.

Larry
 
LarryLuana :

In other words is it more of a selling tactic or is it a worth while treatment which takes extra time? In another does it really make that much difference in the performance of a blade?
Click to expand...

Yes there is a lot of promotional hype about cryogenics, and no, you can't say that just because a knife has "cryo" it is superior to a knife that has not been deep quenched. However if used properly it should benefit the heat treatment by slightly raising the hardness, refining the grain structure and increasing the wear resistance.

-Cliff
 
Thanks Cliff, and with all everyone has said here. I also read the complete thread over on the Bob Dozier forum, and believe I now have a better understanding of the cyrogeinc treatment.
Sometimes even through research it is difficult to find what you are looking for, and thank goodness for these forums, and the great people who hang out here a person can usually find out the answers to the information he is seeking.
Much appreciated :)

Larry
 
Thanks Hotrod for the website. I put in my "favorites" for future reference for myself as well if/when this question comes up again.
Really covers well about all different ways they do the treatment, and what it accomplishes.
Thanks again to everyone, and thank goodness for these great forums:)

Larry
 
Larry
Two- three, two hr. tempers will transform most of the austenite to martensite. D2 is designed to retain some austenite which is soft and will help to make the D2 tough. Many of the processes used to treat steel are very specialized and do not contribute all steels. Cyro will not hurt D2, but does not contribute enough to make a large difference. And the austenite does not transform easily to untempered martensite at a later time, because the carbides are large and do not move very easily. I think the most knowledgeable person about D2 that I know, is Ed Severson of Crusible Steel. You should address some of your questions to him. He watches the forums and will answer you. If not, I will get his attention for you.

Bob Dozier
 
This may be a double post but hope not:)
Anyway thanks very for the great info. I read your complete thread on your forums, and learned a lot from the posts there, nad also from the website www.onecryo.com realizing it is their business so they are going to highly promote their treatment. I took all into account from both, and learned much from both you, and them.
Answered my questions plus more, and now have a better knowledge of what it does, and does not do.
If Ed Severson wishes to post on this subject also it would be appreciated as all views are valued.
Thanks again for your input.

Larry
 
The main advantage of cryo isn't the completion of martensite transformation, it is the enhancement of the wear resistance through the formation of highly wear resistant carbides. Comparisons of cryo vs multiple tempers has shown very large advantages to many steels (more than 100%), D2 having one of the largest gains. I can also offer than gain of small amounts of hardness (1-2 points) with no drop in impact toughness.

-Cliff
 
Cliff

You have been reading too many cryogenic adds. The excess and very large carbides that do not go into solution are the reasion for the high wear resistance of D2. Cryogenic treatment was developed for deminsional stabilization but many claims have been made by people selling it. D2 properly treated does not need it, and only if it is not tempered properly will it gain from it. Large sections and poorly treated steel will gain from it. I am not a metalurgest and I know that you are also not one. That does not make us even as I work every day with these steels and you do not. Your knowledge is scant at the most.
These cryo salesmen are like used car sales men. They will tell you what you want to hear.
Hope you don't take this wrong. It's only to help you in your understanding.

Bob D.
 
As a metallurgist I can say that much of cryo is nonsense. I have read many of the websites of the cryo companies and find them filled with misinformation ,exaggerations etc. The prime use for cryo is to more completely transform retained austenite to martensite.It has little to do with forming carbides . It is highly dependent on the type of steel and the heat treatment .The more complex the alloy the more likely that cryo might be benificial.
 
Thanks Bob. I just read your website and must make comment on cryo treating rifle barrels. There is even more nonsense there, the barrel steel(typically 4140) and its typical heat treatment wouldn't even have retained austenite. As for accuracy, stablizing, stress relieving , how is it that some of the best barrel makers like McMillan have found NO improvement ? I have still not had anyone explain to me how cryo stress relieves when to relieve stress atoms must move and the lower the temperature the less atoms can move. After all the metals industry for a long long time has HEATED steel to stress relieve. As you already know , Bob, there are two problems with steel 1--- picking the right steel 2--- heat treating it properly.
 
Mete

Thanks for the coments. There are things that I don't know and admit that I have no formal education in any thing. But I do have a very good metalurgy libary and read as often as making a living will allow me to. We need to express what we know and learn to listen to people that know what we don't know. I have many of the old books from early 1900's and late 1800's. Very elementry knowledge, but a good place to start befor going on to the newer books which I have most of.

Bob D.
 
Bob Dozier :

You have been reading too many cryogenic adds.
Click to expand...

Trying to find out inbiased information on anything is a real problem. Even using published studies is problematic because the funding can come from people with strong monetary interests, and this isn't always made clear.

Makers can be found who praise cryo highly, some see it as a small possible refinement, some note it as useless and others still see it as actually damaging the steel. However they are all of course selling their technique. Those selling cryo equipment also praise it highly, and those who don't claim you can do the exact same thing with multiple tempers.

However with deep cryogenics (l N2) specific *published* claims have been made, which are not refuted by simply saying "not". This is supposed to be a science not a religion. The carbide contrast comes from a Journal article, which had materials testing on both methods. Do you have reference for otherwise. I would indeed be interested in reading it.

Similar for your comment about the large aggregated pre-critical carbides in D2. Crucible promotes CPM steels as having superior characteristcs (mainly machinability and thus ease of sharpening, but no degredation to wear resistance) due to the lack of segregated carbides and much finer distribution, and has the materials testing to show such performance.

The carbide issue is a complicated one, as there are pre-critical carbides, primary carbides, and even secondary carbides formed during the tempering. I have still not seen a comprehensive treatement of all forms (specific about possible changes in crystal structure) and noting the effect on the final form of what percentage of the initial carbides are dissolved in the soak. Most just reference preventing grain growth as the limiting factor in minimizing soak time.

-Cliff
 
Cliff, let me try to answer your questions. In my research on cryo for rifle barrels, one of the websites referenced a technical paper refering to the carbide formation at cryo (N2) temperatures of TOOL STEEL. Riflebarrels are 4140 which is not even close to tool steel. Tool steel such as Dozier's D2 are sold in the spherodized annealed condition (any other condition could not be machined). At the austenitizing temp ~1500F the steel is held (soak) to dissolve the carbides ,this continues until the austenite is saturated with carbon ( .85% C ) any remaining carbide stays that way. When we quench the austenite changes to martensite which is very brittle until tempered. The tempering pulls some of the carbon out of the martensite forming carbides. The higher the tempering temperature the more carbon forms carbides. The strength and toughness of the blade is a result of the matrix( martensite) Wear resistance is more due to the carbides (at least when you have 1% or more carbon.) Carbide size is important especially when machining or grinding but very large "massive carbides" are seen only in large sections of tool steel ( 12"x12"x12") I think Crucibles CPM steels are are a good idea, I have a Camillus Dominator ordered. Maybe we could get Bob to try the S30V. Anyway my comment has always been, in the real world of tooling , take tooling that has been frozen and some that hasn't and do a proper comparison.There are too many variables to quess. If it works fine ,if not forget it.
 
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