cryogenic treating

Frank Fusco

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This question could probably go in the general forum, but since the term was mentioned with regard to turning tools, I'll toss it out here.
Would turning tools benefit from cryogenic treatment just by dunking in a super-cold environment?
A lot of farmers have semen tanks filled with liquid nitrogen. I sold mine a couple years ago. It would be easy enough, especially with turning tools, to just put into the tank for a minute or two.
Would that be good or useless?
 
Can't answer your question Frank, but if you try it, don't bang the chisel on anything until it has come back to temperature. We played with some stuff when I was in the AF and I seem to recall shattering a piece of steel after dunking it in liquid nitrogen.
 
My understanding is that there is a bit of discussion over cryo treating. Many people in the knife making field advocate it, however there doesn't seem to be any empirical data to support their contention that it "really" improves the process. IIRC, Ron Hock offers treated and non treated blades. For the added cost, especially on a turning tool, I think I would forgo it, but would consider it for a well crafted hunting knife.
 
Cryogenics is a complicated process...

Hello Frank,

I wish it were that easy! ;) Unfortunately, you cannot achieve the benefits of deep cryogenic treatments by soaking a tool in liquid nitrogen for a few minutes. Deep cryogenic treatments do not expose the material to the liquid, only the gas. The process of deep tempering is achieved over a long period of time and requires a computer to achieve the maximum benefits the process can deliver. I recently completed a three and a half year test of cryogenically treated woodturning and woodcarving tools in my studio. I'm familiar with the process, so I will give you a snapshot of a typical (may vary based upon material being treated) deep cryogenic treatment cycle:

A standard deep cryogenic cycle consists of several steps, each "stage" or (ramp) is carefully monitored by the computer.

1.) The initial procedure is called a ramp down. This will bring the temperature of the part being treated down between -300F to -323F over a six to ten hour period of time. The slow ramping is designed to prevent thermally shocking the part. If you simply dip a part in liquid nitrogen, you can create a temperature gradient that can lead to stresses in the surface of the metal as it reacts to the sudden change in temperature. This can lead to cracking on the surface.

2.) The second procedure is called soaking. Typically, this will last between eight and forty hours, with the piece being exposed to the nitrogen gas at -300F to -323F. This is the point where things are starting to change in the metal (like the precipitation of fine carbides and making a stronger crystal structure) and it takes time.

3. The next procedure is called ramping up. This brings the temperature of the part back to room temperature over a period of eight to twenty hours. This must be done slowly to prevent thermal shock and cracking.

4. Next up is a temper ramp up. This slowly ramps the temperature up to a preset level over a specific period of time, much like the tempering process that you would use during quenching and tempering in heat treating. Typical temperatures reach between 300F up to 1100F, depending on the specific metal and the metals hardness.

5. Lastly, we have a temper hold to complete the process. This insures that the tempered part has received the full benefit of the tempering cycle. This will last around three hours, give or take - depending on the thickness of the part. Some pieces may require several of these holding cycles.

As you can see, it's a long and complicated process. However, it can do magical things to many different types of materials. Take care and all the best to you and yours!:)
 
Very interesting reading Steve, thanks for the snapshot :thumb:

Frank, I know it works, they use Cryno on racing cage and bike parts, makes all the difference in the world, it is not cheap, but at those levels it is worth it, and if it did not work the race teams would drop it like a hot stone.

Is it worth the extra money for the average turner?

Well, I can only speak for myself, and I'd say no, but for a pro who spends all day in front of a lathe, extending the working time on a tool from say 5 minutes to 20 or 30 minutes, yeah, I could see that being worth the extra cost, as the tool would last longer, and you would up your production by turning more and sharpening less.

Cheers!
 
steve, what, if anything is to be gained by treating say..o-1 steel over using m-2 or even m-42? is there some transformation that takes place that makes cryogrenic treating preferable to changing steel formulations?
 
Hi Frank.

Currently there is a discussion on cryogenic treatment of tool steel over at Wood Central. I learned a lot about what is OK and what is better. You will probably find it interesting. It doesn't deal with turning chisels in particular, but I think what works for a plane iron can be applied to a turning chisel.

With the blessings of Bishop McMillan :thumb:, here is a good reference that appears on the WC site.
http://www.metalscience.com/techinfo_ASM.php . It is worth looking at, IMO.
 
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As a Sidenote, I remember reading an article on the Cryo process when the fellow first developed and patented the process and was setting up to "License" its use by others. IIRC, the original goal of the process was for stress relieving, but in the testing they discovered the Tempering properties of it also, (or maybe it was the other way around). According to the article they tested it on all kinds of materials to see what would happen, and as a "Quirk" they even put a pair of Pantyhose through the process, and the result was that they were unable to snag or get a run in the hose after they came out of the process. (the way MY wife used to go through those things, I thought the cost JUST MIGHT be worth it).:rolleyes: :D I always wanted to see what other practical (if any) uses they came up with, but never saw anything more on it until Hock started advertising their use of it.
 
If it was easy, everybody would want to do it. :D

Thanks for the write-up, Steve. You answered several questions I've had about cryro treatment.

"simple" is a life long quest for many things. The question is rhetorical and in jest.
But, juging from the responses, I'm not the only one who would have liked the response to be "Yes, just dunk it in liquid nitrogen." That would be great, turn an El Cheapo into top grade tool. But, it's not to be.
There is a brand of knives called Cold Steel that uses cryo techniques in the making of their blades. Their products are expensive, and from Steve's explanation, I can see why.
 
Cryogenic changes...

steve, what, if anything is to be gained by treating say..o-1 steel over using m-2 or even m-42? is there some transformation that takes place that makes cryogenic treating preferable to changing steel formulations?

Hello Todd,

Good and thought provoking questions! I'm not a metallurgist, but I have read a bit about cryogenics in relation to tool steel to see if it was a benefit to me as a woodturner. In general terms, deep cryogenic tempering refines the crystalline structure of the metal. Retained austenite is changed to martensite. Austenite and martensite have different size crystal structures. This means that there are stresses built in to the crystal structure when both coexist.

Cryogenic processing eliminates these built-in stresses by converting most of the retained austenite to martensite. The process also tends to promote the precipitation of small carbide particles in tool steels. These fine carbides act as *hard* areas in the metal with a lower coefficient of friction. This greatly adds to the wear resistance of the treated metal. Some research has concluded the precipitation of fine carbides has more influence on increased wear resistance than removal of retained austenite.

My research and testing has been limited to M2 HSS, M4 HSS, solid carbide and a few misc alloys from automobile engines and suspensions that I use for woodturning tool material. I have not done any research with other tool steels, or tried to quantify differences or advantages of other metals when cryogenically processed. However, the process is used on numerous metal alloys, as well as many other types of materials with demonstrated benefits over the same material that is untreated.

As a citizen scientist, I have to pony up for the cost of my experiments (from the bank of my hip-pocket), so that ultimately is the overall limiting factor and the fact that I have to keep up my production schedule. That's why I tend to do point specific testing (shooting with a scoped rifle vs. a shotgun) to keep me on the straight and narrow and so I don't break the bank.:) That keeps my better half happy and when she is happy, I'm happy!:D It also helps that I can get by on an hour or two of sleep... Lots more time to experiment!:)
 
Thanks for the cryogenics summary Steve!

Can the procedures you described be applied to any type of hardenable steel?

Hello Frank,

The process is used on many different types of metals and other materials including tool steels, golf clubs, CD-ROM and DVD's, musical instruments, automobile engines, transmissions, drive trains, gun barrels, military weapons, airplane components, satellite and space vehicles, metal stamping dies, some types of plastics and lots more... The science is still in its infancy and they are finding new ways to use it everyday. Amazing!:)
 
cryo & other ideas

We did some experiments with copper weld caps and cryo treatments. For welding stainless it was found to greatly increase the longevity of the caps which reduced down time a lot. (saved thousands of $) It also increased the conductivity of the caps by about 10% because it apparently forced the molecules in the copper to line up.
Another treatment for tools that would work well is carbon nitriding. Known in the heat treating industry as nitro-tech, it deposites carbon nitrides in the surface of steels to a depth of 5-8 thousandths (and I think deeper if desired) this layer rockwells around 68-70c and higher. Very hard long wearing surface not disimilar from carbide. I am a little foggy about the exact specs. but I think I'm in the ballpark. I don't recall that it was all that expensive. My brother-in-law is a metalurgist for a heat treat co. and has offered to treat some of my tools. Some day I might take him up on it, seeing as how my gouges keep getting shorter.
 
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