There are some steels for which cryogenic treatments are long known to provide useful property changes. |nd these special cases have long been known and used. Converting retained austenite to martensite, for exampls.
Then there are unsubstantiated claims of all sorts for all kinds of alloys, including some or all steels.
My favorite "claim" from one of the cryoporcessors is:
Yeah, exactly! I've heard about that... Do you have a link or anything?
Why is it austenite gets transformed into martensite at such low temperatures?
I've heard from the company
that cryogen treatment can improve mechanical properties. I also think that there must be a change in mechanical properties that's better than "little or no change". I just didn't understand which mechanisms did the trick, so any explanations are welcome.
Quite a few people believe that these cryogenic treatments are bogus, at least the ones that claim that cryogenic treatment of trumpets and brass musical instruments improve the tone.... rifles cryotreated shoot straighter..... and so on.
I am a firm believer in the ability to be self deceived by some strange claim as cryogenic treatments.
The subject has been discussed here before.
Not one shred of real data on how or why these changes happen.... specifically mechanical data, before and after microscopy....
You should continue to search the internet for more fantastic claims.....
If you encounter any real scientific technical data, quite a few people would like to see it.
Do you have a metallurgical background that would help you sort out truth from claims by cryogenic treaters?
Yes, there are many claims that wear resistance is improved two fold to ten fold.
It would be interesting to see real data on how the material changes, not an empty claim that the grains are made stronger or finer or something else .... with no data backing up the supposed change.
And I think I saw something on google about it :-)
Ok... Then it amazes me if nobody can tell anything about it?
No, thanks. It won't help. That's why I asked the question instead here.
Really? Some people and companies here have made at least one research project about it and somebody at my local university (Denmark) has made a ph.d. in this field and they're doing more research into it.
I've heard from the chief metallurgist at bodycote here why this treatment should help. I just forgot why. It was a very scientific explanation with graphs... I don't believe he lied - and I saw the cryogen chamber with my own eyes...
He should know what he's talking about and since I'm "only" a 6. semester student then of course, I'm not an expert. They've made x-ray diffraction and some other things that I forgot, when they wanted to find out why it improved the mech. properties or at least what happened compared to a traditional treatment.
I think it sounded something like this:
++++++++ cut +++++++ The mechanical properties of certain steels are influenced by cryogenic treatment, i.e. deep cooling to -196?C subsequent to austenitisation and prior to tempering. The ball bearing steel, 100Cr6 (AISI E 52100), has been investigated by means of dilatometry, x-ray diffraction (XRD) and transmission electron microscopy (TEM). Low-temperature dilatometry shows that during continuous cooling the transformation of retained austenite to martensite reaches completion at about 160 K and at 185 K during isothermal transformation, respectively. In situ tempering investigated by dilatometry shows that during the first stage of tempering the contractions are about 20% smaller in the sub-zero treated sample as compared to the conventionally treated material. Stress measurements by XRD imply a more homogenous state of stress in the cryogenically treated 100Cr6.
This thing about the homogenous stress state. I don't really understand it, but they guy at bodycote said exactly the same thing!
I also think that I remember something said about these temperatures at
160 K and 185 K - at least it was very cold...
Also, the guy said that the kryogen treatment was done subsequent to austenitisation and prior to tempering, so what do you think?
Ok, I also don't know what to believe except that I think there should be a difference (I don't know anything about the price compared to the improvement in mech. properties).
I've read that for steel with much carbon content, the mf-line (100% martensitic transformation line) in a TTT-diagram would be lower than room temperature. That means that cooling the specimen down with liquid helium would make a 100% martensitic transformation, even for high carbon content steels. But I don't think that this is the only thing that should make the cryogen treatment good. And I don't know how much better a cryogen treated sample would be compared to an ordinary heat treated sample.
They're still doing some research here, at least:
I think there should be at least one or more publications out there but since they usually cost money, I'm *not that* interested in finding out why the kryogenetic treatment helps... I just asked the question in this NG because I wanted to remember what the guy from bodycote said :-)
That's a very good idea instead of searching on "cryogen treatment" on google :-)
Now I found this page:
I recognize something I've heard about the precipitation of fine n-carbides instead of e-carbides... Actually I think the abovementioned link tells something about what's going on, which was my question.
I'm not sure I really understand the part: "4.2 Mechanism of n-carbide Precipitation"
Martensite has bct-lattice, right?
Why does that chapter say something about a bct-orthorhombic system? The two first figures look more like hcp to me... And the third picture is very confusing - I can't really see what's going on even though I would like to :-)
Perhaps, if somebody understands fig. 9(a), (b) and (c), they can explain it in a more easy-to-understand-method?
Doesn't that mean that the specimen wasn't cooled enough down to bypass the 100%-martensite-line in the TTT-diagram for your 1% carbon low alloy steel?
I've seen you post a lot of information in this NG. What do you do for living and what do you work with, if I may ask?
I do best what I'm doing with you. Getting you to be more specific so a -real metallurgist!- will know where to even start to answer your question.
I'm retired on disability, got hurt, got sick and got struck by lightning, so the railroad decided to put me out to pasture. ;)
I was a "signalman", dug ditches and climbed poles and was the second best;) signal wireman between Yuma and Lordsburg NM.
Scary huh? :) Me wiring RR signals? :) Becareful driving over that there RR crossing, Eugene. ;)
Pretty nutty I'm afraid. :/
I believe my best advise would be for you to ask for, then follow up on, ideas for a good metallurgy book or two (in Danish/German?).
Alvin in AZ ps- we have a little wild pig here the Mexicans named "javalina" because of their tusks can rip any dog to pieces, right now, unless it's a little Terrier that can bite them at will and not get grabbed back or a Great Dane that you train never to "tangle with them" only run up behind them and grab them up off their feet and shake'em like a normal-sized dog would a rabbit. The point is, that's the only two types of dogs we know of that's ever got the best of javalinas! :)
pps- lion and bear dogs (coon hounds) tangle with javalinas and die.
ppps- pit bulls grab them but don't tear themselves loose when they get grabbed back so they lay there in each other's death grip and sometimes die anyway, if not dead, sure as heck tore-up bad. :/
pppps- it's a worth while trick to train your dogs to steer-clear of javalinas and rattle snakes unless it's a Terrier. :)
ppppps- almost all my friends are cowboys (ranchers) since I tend to rub everyone else the wrong way? :/
Yes, you found something fairly scientific looking about the phenomena.
high sliding speed. The specimens after cryogenic treatment show a minimum of wear rate.
precipitation of fine n-carbides.
or substitutional atoms expand and contract, and carbon atoms shift slightly due to lattice deformation as a result of cryogenic treatment.
through the precipitation of fine n-carbide, which enhances strength, and toughness of martensite matrix, rather than the removal of the retained austenite.
Evidently, one of the cryogenic processors made arrangements for good metallurgical investigations, and got positive results. A specific carbide formation apparently confirmed by selected area diffraction.
The compositional alloy requirements for this phase transformation will need to be established empirically. To answer the question of "what steel alloys are improved by this treatment?"
This means that the alleged mechanism of improvement of the sound of brass musical wind instruments will require a different investigation.
hehe... You know how it's like. You hear something and then 3 weeks later you want to remember what was said. I couldn't remember it, but then I found the links I posted to you before and suddenly I remembered having heard some of it... Like this thing with the fine n-carbides precipitating instead of e-carbides...
I don't understand it, but I've heard it before :-)
It's not that important for me to know. I have a couple of books... Perhaps you know one of them: "Materials science and engineering - an introduction" by William D. Callister Jr, it says.
Well, that was too bad. It still sounds like you've got a lot of practical experience, based on the posts I've read from you in this newsgroup.