Double Cryo For Stress Relief?? Mete, this is good one for you

R

rlinger

Joined
Mar 29, 2002
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Okay, heat treat with a cryo included. After grinding decarb or just discoloration if atmosphere controlled would another deep cryo be beneficial in, for example, stress relieving effects of final grinding??

Thanks. RL
 
Roger, didn't you read my posts on cryo ?Here and on other forums I've tried to explain cryo reduces retained austenite , it does not reduce stress.
 
Cool. Why waste the LN.

I'll try to better stay abreast of things from now on.

Thanks :p

RL
 
Roger-

Tim Zowada did an interesting article in Knives Illustrated about his thoughts on cryo helping in stress relief of simple steels. I was just re-reading it the other day.

He used a lab to do the testing for him on O1 test pieces. It was a very interesting article.

I'll find it and post some of the info he reported.

Nick
 
Nick, I have high regards for Tim Zowada. I have been lucky enough to have had him explain to me some heat treat techniques for simple carbons, specifically O1. Following his direction it turned out superb.

Thanks a bunch Nick and I look forward. Do please post what you can find for all of us.

However, I do have faith in what Mete says about this subject too.

RL
 
Originally posted by NickWheeler
Roger-

Tim Zowada did an interesting article in Knives Illustrated about his thoughts on cryo helping in stress relief of simple steels. I was just re-reading it the other day.

He used a lab to do the testing for him on O1 test pieces. It was a very interesting article.

I'll find it and post some of the info he reported.

Nick
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I am still a little groggy from working with Tim Z. until 4:40a.m. the night before last, doing some testing and metallography on a comparitive damascus study we are working on, and I have engaged him in much conversation about his initial cryo results. I too trust that Tim found some interesting anomolous results from liquid nitrogen, but I am also quite sure that I will get my way and we will be doing some more extensive testing together to see what may be going on. Keep on the lookout because I am sure you will hear from either Tim or I in the fiture regarding changes in impact strength in cro treated steels.

Right now I am a big scheptic on most tof the claims being made about cryo, and I will even tell Tim Zowada to "show me" when it comes to those claims, but if it hadn't been for his earlier results I wouldn't even take it seriously enough to want to be shown.
 
I spoke with a Crucible employed metallurgist about a year ago and he mentioned that the company is or will be launching experiments (likely published) to prove/disprove many things on cryogenics in steel, due to the overhyped industry and gross exploitation of the process. One of which, was the *effectiveness of cryo past approx -200°F. Was an ear-perking comment indeed.

Edited to note:

*Or lack there of.
 
I consistantly see a vast change in deep cryo vs no cryo. I notice it seems more pronounced with the ATS-34 and S30V I have worked with. Although I am not experienced in checking grain sizes, I have been impressed by the change in both hardness and ease of sharpening. The edge sharpening part may be me but the the Rockwell tester is not.

As an example, I posted some testing here a few weeks back where two pieces of ATS-34 were heat treated together except that one piece went to deep cryo. The difference was about 3 1/2 points HRc. I just finished heat treating a ATS-34 blade and the difference between 'as quenched' and deep cryo is 3 points HRc. It was 61 HRc as quenched and 64 after 13 hours deep cryo. After tempering twice at 475 F. it is 61 HRc.

RL
 
Deep freeze will not change grain size because the grains are already formed during the initial cooling to room temperature.It will only reduce retained austenite. The effect on hardness is no surprise. Crucible very nicely details various heat treating procedures for S30V and 154CM on their website. They are both excellent knife steels , that's why I own knives made from them !
 
Originally posted by mete
Deep freeze will not change grain size because the grains are already formed during the initial cooling to room temperature.It will only reduce retained austenite. ...
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Thank you for pointing that out Mete. I have seen those who offer cryo services claim that they can refine or reduce grain size and it is at this point they have crossed the line between "still a mystery" and just plain bull! Anybody who says they can change your austenite grain size for you by freezing is either profoundly ignorant of basic metallurgy or a shameless liar looking to take your money.

One thing to be leary of is research or information offered by those who are selling the service, little conflict of interest there. I will only trust research done by myself or an independant lab that is not associated with any cryo service.

Edit- to apologize for any misunderstandings. My above statements, if they appear to be harsh, are not in any way, directed or meant for anybody in this thread. I was addressing those who offer the service. I assume if they are offering the service that they must know something about the inside of metals and if so I say, shame on them, and if they don't know anything about the inside of metals isn't that like me offering medical treatment without so much as cracking an anatomy book?
 
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