Hello,
Who can tell which mechanisms affects steel which has been exposed to a
kryogen treatment and why it improves the mechanical properties, for
instance after heat treatment?
Is it expensive compared to other treatments?
Med venlig hilsen / Best regards
Martin Jørgensen
Which cryogenic (kryogen) treatment?
Which Steel?
Which properties?
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:
I don't know. How many are there? Just pick one.
Just pick one.
What can be done with the treatment?
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
formatting link
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.
Med venlig hilsen / Best regards
Martin Jørgensen
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.
Have fun.
-snip-
Yep, exactly... I've heard about them :-)
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:
formatting link
++++++++ 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:
formatting link
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 :-)
Med venlig hilsen / Best regards
Martin Jørgensen
That's a whole different topic now even though "cold temperatures"
are involve with both! :)
Yes. ;)
I think you'll know and see the difference in all this, as soon as
you study up on-> "retained austenite". :)
I call my process a "cold treatment" to keep from getting it
confused with the old gun barrels and old horns that are being
"improved" on years after manufacture.
In my "hobbist" method a 1% carbon low alloy steel right after the
quench is put in the freezer at ~-5F before any tempering operation
it's important to keep the steel's temperature "going down".
After you've done some studying on this you'll be able to word the
whole process better than I ever could. :)
There is an eleavated hardness that is obtained ~1+1/2hrc that
remains through the later tempering operation and no-decrease in
toughness, both.
Alvin in AZ (high carbon steel metallurgy as a hobby!:)
ps- what am I nuts? :/
-snip-
That's a very good idea instead of searching on "cryogen treatment" on
google :-)
Now I found this page:
formatting link
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.
Of course.
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?
You tell me :-)
Med venlig hilsen / Best regards
Martin Jørgensen
Only once a week or so do I get on the internet using Windows.
I'll check it out as soon as I get a chance.
Wow, it went from getting the voodoo-cryo-treatments confused with-
cooling fresh quenched steel to reduce retained austenite... now
jumping directly to that question?
You've got me confused with someone who knows something. :)
I'm aware of what you are talking about but never studied it well
enough to explain it, never figured I'd need to. :/
Voodoo cryo treatment:
Cold treatment to reduce retained austenite:
And? ;) "because the austenite will become stabilized and more of
it will be retained only to be unstabilized and decompose later into
un-tempered martensite (some of it anyway;)"
You need a good book?
It's only a theory that the 100% line actually exists. :)
I am just getting it lower into that area, and so making more
martensite with no reduction in toughness, both.
That's about all I can say -for sure- about what I'm doing with the
1% carbon steel (1095), O1 tool steel, 50100-B (W7) and
8670-modified (cheap L6;).
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?"
NIce work.
Thanks.
This means that the alleged mechanism of improvement of the sound of
brass musical wind instruments will require a different investigation.
-snip-
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 :-)
-snip-
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.
-snip-
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.
Med venlig hilsen / Best regards
Martin Jørgensen
Dear Martin,
I work for Bodycote (Materials Test Division - not the Heat Treat
Division) Can you please tell me the name of the "Chief Metallurgist"
you talked to about the cryogenic treatment?
snipped-for-privacy@bodycoteusa.com
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