Cryogenic Treatment - Technical Information 3

[mewhg]

In reference to my previous post on 'Cryogenic Treatment effect on Hardness' can someone point me to some good reference materials on cryogenic treatment? I know there is a reference to a paper in my "Physical Metallurgy" Book that I will track down.

Metman, I am especially interested in your comment: <<Transformation to Martensite is not time dependent rather it is only temperature dependent.>>

Thanks again,
Bill

 

[metengr]

The ASM Metals Handbook Desk Edition (2nd Edition) has a brief summary on "Cryogenic Treatment of Steels" on page 980, under the heat treatment section.

<< typical cryogenic treatment consists of a slow cool down (at ~4.5 deg/min) from ambient temperature to liquid nitrogen temperature. When the material reaches 80 deg K (-315 deg F), it is soaked for an appropriate time. The soak period is 24 hours>>

The article goes on to describe the benefit of increased wear resistance based on an evaluation of five high-carbon steels.

Here is some additional information;

http://web.vtc.edu/mt/114/Research/Russ/DCT.htm

http://www.efunda.com/processes/heat_treat/matl_modify/cryogenic.cfm

http://www.energy.ca.gov/process/pubs/cryog_processing_tc113571.pdf

 

[metman]

mewhg

Normally I would champion metengr's comments as he has contributed a lot of good stuff. However, in this instance if you read the first link that he provided -- I don't know about the other two because I did not make it that far -- you are likely to get confused. The author of that article has mistaken a little bit of knowledge about metallurgy to thinking it is a lot of knowledge and has mixed fact and fiction, braod unsubstaintiated claims, etc. It smacks of sales talk and cannot be trusted and I believe it simply does not even belong on this forum.

If you want to understand the process of transformation from Austenite to Martensite in carburized 8620 it helps to look at a TTT diagram. Maybe metengr will provide a link for one. He is quite handy at helping out on these things. TTT stands for Time, Temperature, Transformation and the curves show what happens to steel when it is cooled from Austenitizing and held isothermally at different temperatures. If the steel is quenched rapidly enough to miss the "nose" of the curve, then 100% Martensite is theoretically achievable if the steel is cooled to below the Mf (Martensite finish temperature). If not quenched, the time lag will allow softer transformation products. Once the steel is quenched to the Ms (Martensite start temperature), Austeite begins to transform to Martensite and continues to transform as the temperature is depressed until th Mf temperature is reached. In carburized 8620 as in many steel alloys carburzed or not, the Mf temperature resides below room temperature. Hence subzero treatment is required to reach the Mf temperature. Why it does not require time for this A-M transformation, I have forgotten but fairly certain there is a thread on this forum that exlains it. I don't have the Mf for carburized 8620 handy but will guess that it would only require dry ice temperature to transform it.

There is a statement in the link metengr provided that talks about thermal shock. There certainly is such a thing but I don't believe that it would require 24 hrs to alleviate the effects of thermal shock and since Martensite transformation is not time dependent, it all becomes mystical. when people start talking about "cryo" treatments I get edgy just in case you haven't noticed. I am sorry but there are legitimate discissions about cryogenics and then there are others.

end of rant

 

[metengr]

metman;
The first link was indeed an error on my part. I had reviewed the link and had mistakenly copied it into one of my download files. I believe it is from an elementary class in metallurgy.

Please review the 3rd link - it is from EPRI and provides a decent overview of cryogenic treatment.

 

[NickE]

Another Thread discussing Cryo-Treatment.

thread330-58901

Nick
I love materials science!

 

[EdStainless]

For different alloy the temperature that you should use is different. For some alloys there is no benifit to going below -80F. Other alloys may need for you to go clear to LN temp. Once you reach the 'right' temperature then you need to allow enugh time, but you can't trade one for the other. Often the times are short since you have set up conditions where the reactions are highly favored.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[Carburize]

It depends which calculation method is used for Ms and Mf but one estimate would put the Mf for typical carburizing grades at around -50C for 8620, -70C for 4320 and -100C for 9310.

 

[Carburize]

Above post is based on the nominal chemical analysis for C, Mn, Ni, Cr and Mo for each of the three alloys and a case carbon content of 0.8%

 

[Carburize]

Should really have given the source reference also!

Andrews K W "Empirical Formulae for the Calculation of Some Transforamtion Temperatures" Journal of the Iron and Steel Institute, 203. Part 7. July 1965, 721 - 727

 

[metman]

metengr,
Thanks for the clarification.

You said, "Please review the 3rd link - it is from EPRI and provides a decent overview of cryogenic treatment."

Agreed. Also the second link is a nice summary.

 

[m610]

I found this forum while Googling for "Cryogenic Treatment of Metals". So now you may hear more from me from time to time.

I have been curious about this technique for a while and yesterday, after seeing an ad in SportsCar, I checked out the

http://www.evanperformance.com

site and read their description of the cryo-treating process. The metallurgical explanation was such a mess that I offered to help them clear things up. I didn't get very far. Anyway, left me with the distinct impression that maybe the technique was bogus, or at least the claims were exadurated.

Today, I found a descent, balanced, and cautious description of the process at

http://www.onecryo.com.

Read their "A Brief of Cryogenic Processing", which was excerpted from a Battelle report. Excellent. But then if you click "How" in the menu at the top of the screen the claims, and the metallurgy, disappoint, with statements such as "Even performed properly, heat treating cannot remove all of the retained austenite (large, unstable particles of carbon carbide) from a steel." Click the "Metallurgy" link at the bottom of the page and you see statements like "resultant tight lattice structures are precipitated from cryogenic treatment" which are attributed to an NBS report.

There might be something to this cryo-treating, but its proponents aren't doing themselves any good in the way they explain the process. I might try to make it the topic for an upcoming ASM chapter meeting and possibly even a project for an undergraduate laboratory course.

 

[TVP]

m610,

That sounds like an excellent idea. This is a field in desperate need for some scientific experimentation and characterization.

 

[metman]

m610,

It appears you are a newby here. Welcome aboard and thank you for your apt description of the situation. I second TVP,s comment. At some point a FAQ would be nice having a matrix of claims vs (fact, questionable/unsubstantiated, false.)

 

[m610]

Thanks.

Our students are meeting tonight to form a student chapter of ASM/ACerS/TMS and I have talked to a few of them about making this an independent research project for next year. We have xrd that can check residual stress and retained austenite, tensile, hardness and Charpy testers, we can adapt one of our polisher/grinders (Ecomet 3 with power head) for wear tests, can measure density pretty accurately, and of course metallography, OM, and SEM. The students sounded pretty interested and might go as far as to try to publish the work at an ASM conference.

Meanwhile, I am going to keep digging around for cryo-treating sites and logging the erroneous and pseudo metallurgial text and claims each company makes for the benefits of their process. Some could turn out to be OK, but after reading that austenite is a carbon carbide, well, who knows what will turn up.

 

[metengr]

m610;
Some pleasure reading I found that may be of interest to your students regarding evaluation of cryogenic treated M2 tool steel;

http://www2.bc.edu/~huangje/MSE-Steel.pdf

PII: S0921-5093(02)00165-X

 

[Frederick]

Well, I guess that I have to put my $.02 in. First, if the students who are researching cryogenic processing for the upcoming conference would contact me, I would appreciate it. I am the ASM Cryogenic Processing sub-committee chairman, and will assist them in getting their research published whether it is positive or negative about cryogenic processing.

Second. There are a lot of silly statments about cryo out there, but just try to get people together and hash things out. All cryo processors would be better off if they stopped the wild claims and published things that can be respected. But they all have their "secret" formulae and a lot of them claim to have invented cryogenic processing, therefore they do not want to "help the competition." By the way, I have traced cryogenic processing back to Germany in the 1930's at Junkers.

Third. I would appreciate it if you would take a look at our web site(

http://www.metal-wear.com)

and our discussion about the process under the heading "More Detail". I would greatly appreciate feedback, good or bad.

Fourth:
There is a lot more happening in Cryogenic processing than just transformation of retained austenite. Cryo has been shown conclusively to increase wear resistance on copper, pearlitic cast iron (brake rotors), aluminum, and abrasives such as aluminum oxide and diamond.

Its good to see some discussion on this subject.

 

[metman]

As a student I joined ASM, American Society for Metals, about 1960. Some years later it was changed to "A Society for Materials International." Today on a technical forum, a gentleman who is chairman of an "ASM" subcommittee provided a link to the company he works for and in their blurb, they repeatedly refer to ASM as "Amercan Society for Materials." I searched the "ASM International" web site a little but could not find the actual current offical spelled-out name of of ASM org. On my current membership card, under the ASM International logo, it says The Materials International Society. in some of the newsletters from our local ASM chapter, the original title, American Society for Metals, is used. Will the real ASM please stand up and be counted? Is there such an organization named American Society for Materials?

Confused

 

[Carburize]

metman- I see you posted on the asm-intl.org page as well and hopefully you will get the "official" answer however, my personal understanding is the the registered name of the society is ASM International. This is similar to the old Institute of Welding in the UK which became The Welding Institute and is now formally registered simply as TWI.

 

[unclesyd]

Fredrick,
You should probably look a little further back for the beginning of Cryo Processing.
Henry Ford let his CI motor blocks age thru at least one winter in the early 20's.
The earliest reference I found is the little old Swiss Watch Makers aged their steels on the mountains for several winters to stabilize the material and for wear improvement.
You are probably correct in saying Junkers was the first to publish anything on the process.

In earlier post's I mentioned that we achieved tremendous improvement in wear on small diameter(.0090") drills, broaches, and plugs. I'm still trying to get my notebooks released as there is a lot of good documented information on Cryo Treatments as related to our process. Cryo treatment is still the normal on all our components made from D2 and H11 for dimensional stabilization.

 

[Frederick]

Metman:
I looked at the history of ASM International and it does not specify what the M stands for any more. Its just that I recall a lot of emphasis in the late 1980's in the Chicago Chapter that the M now stands for materials. Metals Park in Ohio was renamed Materials Park, etc. If ASM comes out with a definitive answer, I will change the website to reflect it. However we will still put in some description RE: ASM being a materials oriented society for those who visit the website who are not familiar with the society.

UNCLESYD:
I appreciate your support of cryogenic processing, but the accepted definition of cryogenics is that it involves temperatures below 120K (-243F, -153C). This definition is accepted by the CSA (Cryogenic Society of America), and was adopted by the XIIIth Congress of the International Institute of Refrigeration. So Henry Ford and the Swiss watch makers, while making use of cold to improve their products were not getting the advantage of cryogenics.

There is an important difference between cold treating, and cryogenic treating. The cold treating of steels is usually done just to convert retained austenite to martensite. The US Army Aviation and Missile Command established that the cryogenic treatment of cold treated 9310 steel (Carburized) doubled the life of the material in a pin and disk wear test. Cold treatement does not have much effect on copper, silver, titanium, aluminum, diamond, aluminum oxide, etc, but cryogenic processing does.

The above may sound like splitting hairs, but you would not believe the number of people who have told me they are already using cryogenics when they are merely using cold treatment. This is also the source of the phrase I hear all the time that "its only good if you have bad heat treat." Heat treaters will often claim that they have not seen the results of cryogenic processing after cold treating, so it must be some sort of scam. If the truth be known, they did not do a real cryogenic process.

This process is very missunderstood, largely because of wild claims used to promote it. There were also those who felt parts could just be dipped in LN2. I had a "scientist" tell me he saw no difference in a spring he had dipped. He did not read the literature (notably from Russia) that found that results are pretty variable for items that are dipped. Thermal shock is a real and often dangerous prospect.

Sorry to ramble on. Thanks to all for a good discussion, and if anyone wants to join the ASM International Cryogenic Processing Sub-Committee or just has suggestions on how we can make this process less likely to collect flak, feel free to contact me.