sub zero

[Raymond Johnson]

This question has been on my mind today and i'd just like to know what a few of you guys think.

Does a cryro treatment do anything to help a carbon steel. If yes, then when to do it and for how long.

 

Thanks

[Chuck Bussey]

I have a client that is a senior materials research analyst and that has been the subject for several appointments. This method of treating materials is still in it’s infancy. We are not sure exactly what changes. Yes, cold treating carbon steel helps it for the characteristics of a knife. I think that we will find that the cold treatments are going to be as varied as heat treating methods. As to when and how, that is proprietary. What is really cool is cold application of polymers and abrasives. I know that it is not much of an answer but that is the best of my knowledge.

[bigokie]

Don't know if this will help any but they have been cryo treating rifle barrels for a while. On one of the cryogenic rifle treatment sites they claim it relieves internal stress, helps for easy cleaning, and extends barrel life. I know that this is different but maybe it might help in the understanding? Or it might just make it clear as mud! Matt

[kb0fhp]

A quick search using Google and "snake oil" will uncover multiple references to cyro treatment.... (That ought to start some flames!)....just kidding.

 

The use of a sub-zero treatment - typically 24 hours at -100F is very effective in reducing retained austenite. It is a standard practice for aerospace steels, or those that are prone to retained austenite. THe times and temperatures vary a bit, but this is the essential process. It does work.

 

There have been claims that cryo sweetens the tone of brass instruments, reduces stresses, or cures global warming. Most claims are anecdotal, and do not have independent research or study behind them to validate the claims. At the present time, any claim other than reducing retained austenite is bogus.

 

IMHO

 

Scott

[Howard Clark]

Yeah Scott !!!!! I would also be more inclined to listen if the research wasn't all either done by, or paid for by, the people selling cryo services and gear. I'd like to buy you a drink sometime, somewhere, just for this !

[Raymond Johnson]

I'll buy you both a drink if I can sit in on the conversations.

I mean it really! Not a joke!

I think for the scope of my question, you and the other have answered it.

And this not the first time I have ask this one of myself or others. I am starting to use this treatment more and more with what means I have.

I am a firm believer of tempering three time with desending tempatures, and I usally throw the cryro in after the first temper. I have been told that the lower and longer the better, but some time at low temp is better than none. I'm just doing the best I can with what I have at the moment.

Thank you for your help.

[HSJackson]

Knives Illustrated magazine had an article on cryo-treating by Dr Jim Batson in the Aug 2006 issue. He did lots of testing and came to the conclusion that it improves edge holding and reduces micro cracking and chipping. Some steels responded better than others. A-2, 52100, O-1, and D-2 showed the most improvement in wear resistance in that order. Also -310 degrees showed a dramatic improvement over -120 degrees with all the steels.

He also explains the mechanism of what's going on in the steel with the carbon but it's kind of long to retype here. Basically, the carbon finds a more ideal position in the metal matrix as it's brought back up to normal temp.

Anybody know how cold dry ice and acetone gets?

[Mike Blue]

I'll buy the second round.

 

I think Dr. Batson was referencing some research that came out of Louisiana, not necessarily experiments that he had done himself. Sadly, all the people talking about cryo treatments don't explain the conflict of interest bit very well, as Howard noted. They also don't really discuss much of the finer details of how to make it work really well.

 

I'd love to have all the players in this argument make up their blades and show up in Colorado at Spyderco for a CATRAL showdown.

 

Acetone/alcohol and dry ice will get down to the minus 125 Fahrenheit range.

 

Having read Dr. Verhoeven's book on Heat Treating for Bladesmiths, the chapter on carbon steels does not mention cryo treatment of any kind. The chapter on high alloys, e.g. stainless', does discuss cryo. Hmmm.

 

Given the cost of the equipment, there may not be any practical benefit for an ordinary knifemaker. Someone like Paul Bos who is setup with all the toys and works exclusively with stainless materials will likely see more benefit. But, carbon steels heat treated correctly, will likely have little enough retained austenite that it won't make enough difference to justify the cost.

 

Historically, there are likely millions of serviceable blades that did, and still do, just fine without liquid nitrogen.

[Raymond Johnson]

Man! I'll think twice before I ask another question.

Thank you everybody for your thoughts on this matter.

I am currently using both carbon and stainless steel and I am doing the best that I can with what I have. I don't have an opinon on this either way, but I am curious.

[kb0fhp]

I would be interested in reading Dr Batson's article. Since the carbon in any steel is located in the intersitial spaces, I am a bit confused about it finding a preferred space.

 

Cryo does work in converting retained austenite - all that is required is to use a temperature a bit below the Mf temperature. For alloys like 4340, 300M and HP9-430 (9% Ni, 4% Co, 0.30%C) - used in landing gear, as well as the newer AerMet 100 and AF1410, the temperatures are -100F for 24 hours.

 

I depends on the steel - if it has a lot of nickel - then it would be a likely choice for a retained austenite treatment. Otherwise I would save my money. Unfortunately, there are a lot of people who REALLY believe - even to the point of fanaticism....and can't listen to reason, or independent study. My mind is not made up - but I need to be shown valid, peer reviewed literature to show that it works.

 

Scott

 

BTW, for an interesting discussion of cryo treatment (that got a little heated) look at :

 

http://forums.swordforum.com/showthread.ph...;highlight=cyro

 

BTW - serveral questions I posed were never answered....

 

Scott

[Raymond Johnson]

Thanks everyone.

Edited July 2, 2007 by Raymond Johnson

[HSJackson]

Well I managed to find the article and it does rely on experiments done by Dr. Randall Barron, a professor in the Mechanical & Industrial Engineering dept at Louisiana Tech.

 

The first mechanism is the transformation of retained austentite into martensite which is tempered at +300 after the cold soak.

 

The second mechanism is the formation of very small carbide particles called eta carbides dispersed in the martensite structure between the larger carbide particles (epsilon carbides) present in the steel. The small, hard carbide particles within the martensite matrix helps support the matrix and resists penetration by foreign particles in abrasive wear.

 

It was a Mr. Robin Rhodes who is a provider of cryogenic treatment services, who described the free carbon relocating to atomically open locations within the chemical lattice of the iron-carbon matrix as the metal warms up from -300.

 

The third mechanism is internal stress relief. Although the article didn't provide any detail of exatcly how this happens, it supposedly reduces the chances of micro cracks that can lead to fatigue failures.

[kb0fhp]

Any chance you could post the article? I would really be interested in reading it.

 

Thank you

 

Scott

[HSJackson]

I only have a paper copy of the magazine and unfortunately, after upgrading to Windows Vista, my old HP scanner doesn't work, and the HP support site says there will be no Vista compatable drivers released for this product. I guess I need a new scanner.

I guess I could try taking a pic with a digital camera and e-mail them to you. Photobucket won't post big enough files to read the text.

[kb0fhp]

BTW, my email address is kb0fhp@comcast.net

[kb0fhp]

I got the paper - thank you. Essentially it described two mechanisms - first at -120F, the mechanism is conversion of retained austenite. At -320F, two mechanisms: the transformation of retained austenite to martensite, and the second is the precipitation of fine eta carbides between the larger carbides. He also indicated in passing that there may be a stress relief occurring.

 

I am not happy with the explanation given - doesn't sound correct about carbon finding more preferred sites....the low energy sites are the intersitial ones - where the carbon is already residing.

 

I need to do some research on the formation of eta carbides and the likely hood of it happening at -320F.

 

I have never disagreed with the premise that -120 F would work. Nor particularly at -320 F (mostly due to conversion of retained austenite) - but I am not sure of the precipitation of eta carbides. Perhaps because of the lower temperatures, the precipitation of the carbides occurs from the conversion of retained austenite.....and the associated carbide precipitation.

[guarnera]

This question has been on my mind today and i'd just like to know what a few of you guys think.

Does a cryro treatment do anything to help a carbon steel. If yes, then when to do it and for how long.

 

Thanks

 

 

Hello All,

First of all, I'm not trying to contradict Mr. Clark. Whom I Consider a heat treating god. I think he knows more then I could ever hope to know about heat treating. Or to contradict anyone else here, whom I'm sure know way more then I do. I'll buy the retained austenite in alloy steels because it is something that can be measured in the hardness of the steel with and without treatment. But a certain master smith told me once that he thought it made a tougher blade using carbon steel. Ok, he didn't have any laboratory proof of this. But all I'm trying to say is I think there has not been enough research done in this area to conclusively say that it really doesn't do anything other then change retained austenite to martensite . I think research needs to be done in finding the best cryo treatment and standardizing it. But that will take a lot of research to find out exactly what going on and what the best type of cryo treatment is. No disrespect meant to anybody.

 

Tony G

[kb0fhp]

I don't have a problem with that at all - my problem is marketing it like snake oil, and providing anecdotal stories instead of real research by independent people - instead of just hawking their wares.....

 

There must be something to it - otherwise so many people wouldn't claim otherwise. Unless a whole lot of people are fooled by a bunch of placebos...

 

 

Scott

[TJ_Ranatza]

I did a lot of studying on this when I was in the "Strength of Materials" phase of my Mechanical engineering degree, I posted a write up on it in my blog Scary sharp!: Cold Hardening

It comes complete with a link to the original paper and some nice little diagrams! Easily the most easy explanation with real world examples that I have ever found on this subject!

[Mike Blue]

I don't have a problem with that at all - my problem is marketing it like snake oil, and providing anecdotal stories instead of real research by independent people - instead of just hawking their wares.....

 

There must be something to it - otherwise so many people wouldn't claim otherwise. Unless a whole lot of people are fooled by a bunch of placebos...

Scott

 

And that's the problem. There are a good many research studies that have significant findings that do not have any practical value in the real world. The findings work in the lab but cost too much, or take too much time or the tooling investment isn't recovered by the work done. The only folks who make any money are the one's selling the equipment.

 

And, yes, people are fooled by placebos. Even very smart, intelligent, well educated people who should know better. People take lots of vitamins that have been shown not only to be ineffective, but possibly dangerous in quantities that are primarily only benefitting the company producing the vitamin. But, the one time, someone took that pill and felt better, is enough to overcome volumes of research to the contrary. The same can be said of cryo treatment of steel.

[kb0fhp]

I did a lot of studying on this when I was in the "Strength of Materials" phase of my Mechanical engineering degree, I posted a write up on it in my blog Scary sharp!: Cold Hardening

It comes complete with a link to the original paper and some nice little diagrams! Easily the most easy explanation with real world examples that I have ever found on this subject!

 

Based on the table of materials that showed a considerable improvement, and comparing it to those that didn't show an improvement - one thing is clear. The materials with strong austenite stabilizers tended to show greater benefit. Those that didn't have any strong austenite formers or stabilizers did not show any improvement. If I get time, it would be interesting to correlate the Mf temperature to the improvement and the treatment temperature. I suspect that the lower the Mf temperature, the greater the improvement via treatment at very low temperatures.

 

Further, most of the articles sited were mostly the free type trade journals - with articles written but not peer reviewed. Only 2-3 of the Journals were really peer reviewed - These were Jounal of Heat Treatment (the old Wolfson institute - now operated by IFHTSE), and J. Mat. Sci.....

 

Also this article above was written as a marketing piece - although a good one - to sell Linde nitrogen or to buy their equipment.

Edited September 13, 2007 by kb0fhp

[R.H.Graham]

Based on the table of materials that showed a considerable improvement, and comparing it to those that didn't show an improvement - one thing is clear. The materials with strong austenite stabilizers tended to show greater benefit. Those that didn't have any strong austenite formers or stabilizers did not show any improvement. If I get time, it would be interesting to correlate the Mf temperature to the improvement and the treatment temperature. I suspect that the lower the Mf temperature, the greater the improvement via treatment at very low temperatures.

 

Further, most of the articles sited were mostly the free type trade journals - with articles written but not peer reviewed. Only 2-3 of the Journals were really peer reviewed - These were Jounal of Heat Treatment (the old Wolfson institute - now operated by IFHTSE), and J. Mat. Sci.....

 

Also this article above was written as a marketing piece - although a good one - to sell Linde nitrogen or to buy their equipment.

 

Context has to be considered also IMO.

Big difference in a blade section to that of a long cylindrical one, first of all.

 

I tested cryro againt different quenching set-ups many many years ago and found it helped some in very highly alloyed steels that were air-hardened in particular, and a tiny bit in some that were oil quenched.

In low-alloy and simple steels I saw no practical difference.

Basically, in the high alloy steels, I was left with the impression that you could air-harden and freeze to get rid of the retained austenite, or quench it fast, and achieve much the same thing.

 

But what do I know.

[TJ_Ranatza]

Context has to be considered also IMO.

Big difference in a blade section to that of a long cylindrical one, first of all.

 

I tested cryro againt different quenching set-ups many many years ago and found it helped some in very highly alloyed steels that were air-hardened in particular, and a tiny bit in some that were oil quenched.

In low-alloy and simple steels I saw no practical difference.

Basically, in the high alloy steels, I was left with the impression that you could air-harden and freeze to get rid of the retained austenite, or quench it fast, and achieve much the same thing.

 

But what do I know.

 

 

True, but when I do work in alloyed work after the quench I pack the blade/tool in dry ice for about an hour then temper, I have never done any thorough testing but the few times that I did a side by side their was enough difference that it made a believer out of me.

 

Oh, the only steels I have used it on is some Timkin bearing steel and a few little knives made of D2.

[kb0fhp]

There is never any question that cryogenic treatment works for recovery of retained austenite - as such I recommend it. But I have problems with the antedotal stories of improving copper wire - making golf balls that fly further, etc.

[Mike Krall]

What are the chemical characteristics of steels that would indicate retained austenite (besides a lot of nickle)? Are there any ways to, at least roughly, calculate Mf? Are there tables of Ms/Mf for steels available?

 

Mike