Need Cryo treatment

O

oldwolf

Joined
Dec 29, 2002
Messages
617
Anyone in the Sacramento, Ca. or Reno, Nv Area have a Cryo set up? I need two ats-34 blades done. Really don't want the shipping it away waiting time for these.
 
I cant help with that location query but I'd caution not to see it as a commodity process. Like heat treating its different to what times at temps, temp change rate, deep cryo vs cryo etcetc.
 
Cryo works by converting retained austenite to martensite. If it does anything for you in this application - it would then need to be tempered to temper the new martensite.

It is unlikely to do much for you. Cryo needs to be a part of the heat treat, used as a part of the quench before full temper, otherwise the retained austenite will stabilize and will not convert.

To be used properly, cryo is a component of a heat treat - not an after the fact add on.
 
Nathan, That's interesting as there is a Co. nearby that does cryo and advertizes that most tools and chainsaws will benefit from it . Smoke and Mirrors?
 
oldwolf said:
Nathan, That's interesting as there is a Co. nearby that does cryo and advertizes that most tools and chainsaws will benefit from it . Smoke and Mirrors?
Click to expand...

Yes. Probably 90% of it is false. I'm familiar with the claims.

However:
Cryoed rifle barrels are not really more accurate
Cryoed golf heads won't really hit further
Cryoed race car parts aren't really faster
Ground up rhino horns won't really give you stronger - oh wait, never mind

These things are just in these people's heads. And the folks who stand to profit from doing it.

The metallurgical change to the metal will be to convert what amount of retained austenite that can convert over, which on a part that has already been fully tempered will not be much. The changes to the performance of the part will be imperceptible.

There are applications for it. Some mold components are made of M2 HSS which frequently has 20% RA or more. The cryo won't convert much of it except for a small % that is borderline. But by converting it, the long term dimensional stability is enhanced (because it won't convert on its own later), which on a 20" ejector pin can be important.

Cryo, as it pertains to knives, can make a somewhat stronger more homogenous structure by reducing RA and maximizing martensite on steels and HT that suffer from RA. But it has to be used as a part of the quench, or the RA will mostly not convert. I know this as a fact from personal experimentation.

Freezing a finished blade is a waste of time.



Edit to add: I use cryo on D2 for improved edge stability, and the effect is dramatic on D2 that has been tempered in the 400-500 range. High tempering temps decompose RA, but there are drawbacks to using the secondary hardening hump. Low tempered D2 without cryo does not work well (for me)
 
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Nathan, what about a snap-temper before the cryo? Mete says that the A2 should be O.K. with the cryo without the snap temper. Brad from Peter's HT says do a snap-temper at 300F for 2 hours before the cryo. I don't want the retained austentite to stabilize before the cryo, but, I don't want my blades cracking in the cryo, either.
Since you have experience with cryo, and I have zilch, please give me your opinion.
Thanks,
Mitch
 
You're obviously the nervous type. 300 F snap temper certainly won't hurt things.
Understand that some steels are more prone to cracking than others.
 
mete said:
You're obviously the nervous type. 300 F snap temper certainly won't hurt things.
Understand that some steels are more prone to cracking than others.
Click to expand...

Yes, Mete...I guess I am. Let's see....
1. Forge the steel
2. Spherodize anneal for a million hours in my Evenheat.
3. Rough grind.
4. Stress relief for another couple hours.
5. Heat treat; Very slowly ramp up to pre-heat at no faster than 400F/Hr.
6. Hold at pre-heat for 30 mins.
7. Slowly ramp up to hardening temp.
8. Hold for 25 mins.
9. Quench.
10. Cryo.....PING!

Yea....I'm "nervous".:D
 
Troop said:
Nathan, what about a snap-temper before the cryo? Mete says that the A2 should be O.K. with the cryo without the snap temper. Brad from Peter's HT says do a snap-temper at 300F for 2 hours before the cryo. I don't want the retained austentite to stabilize before the cryo, but, I don't want my blades cracking in the cryo, either.
Since you have experience with cryo, and I have zilch, please give me your opinion.
Thanks,
Mitch
Click to expand...

I don't know the answer to your question. I've played with A2, but not enough to know the answer. D2 (the steel I mainly work with) is bad about RA due to all the alloying, lots of chrome and very high carbon. A2 is much more moderate.

Heat treaters are going to want to snap temper because they are less concerned with edge retention than they are about breaking and warping.

I have a great deal of respect for mete and I certainly don't want to disagree with someone much more knowledgeable than I am on his subject of expertise. That said, I personally am not certain the snap temper won't hurt things. It will probably result in a more durable blade and will practically eliminate cracking risk - but in my own personal experience with D2, I have found that just about any damn thing will result in more RA. With D2, there should be no delay, the quench needs to be a continuous drop to Mf (-100 ish) or austenite will start to stabilize. So with D2, I have found that any delay, and especially a hour or more in temper, will reduce the about of austenite that will convert. A2 may not be like that, I don't know.

This is just my opinion. My advice would be to do the experiments yourself, or go with the advice of the folks more knowledgeable than I am.
 
Harvest Moon, I always do a cryo cycle as soon as the blade cools to room temp. direct into the LN2 and hold for at least 2 hours and sometimes overnight if I am ready to quit at the end of the day. Early on when trying to learn all I could about heat treating I read in several sources that you have to keep the process moving down in temp and any hold time will result in stabilizaton and even a cryo cycle later will not resolve the RA. I have done this on thousands of blades with CPM S60V, S90V, 154Cm, CPM 154, 10V, S110V, CPm M4, S30v, S125V, D2, A2. I can report that I have never had a blade crack as a result of a LN2 Cryo cycle. It is important I think to round off all the edges and not have any thick flat sections next to deep hollow grinds ect. I don't forge so can't commemt on how that process may change things and increase the risk for cracking in a cryo cycle. Does a cryo cycle make a better blade? Everyone will have to determine that for themselves and their particular process. I do it as a matter of Quality Control and feel like I get a better temper response when working with almost 100% martensite.. Hope this helps to calibrate some.. Phil
 
I've only heard one maker say they had a blade break in cryo.
 
ive done soem greal bad things to blade in heat treat and have just two times cracked blades one was oil quench air quench steel and the other was at a plunge cut on a over the top heat treat (it was jsut too different of steel thickness)
 
I cant attest to the fact that it will help further reduce the retained austenite as I have paid for metallographic examinations of test blades.

I have conducted quite a bit of study on this process. I have learnt that while in some heat treating processes temperature is critical and not time, conversion of unstable austenite at deep cryo temps being -200C is in fact time critical. I have gotten better results leaving it at -200C for 24 hours and slow rates of cooling / heating going down and up to atmospheric temps.

I note that there is other heat treating methods which will help with reducing retained austenite.

I have never done tempering then cryo then tempering - I have also quenched then immediately into the deep cryo. I note that some do it within the tempering cycle but I cant comment on that personally.
 
Can ATS-34 reach full hardness by using the 975F triple-temper, w/o cryo?
 
Thanks for all the responses, guys. It looks like I've got to go straight to cryo as soon as ambient is reached.
Phil, good to hear from you. Hope you're doing well.
- Mitch
 
Codt, I think you can get pretty close to full hardness. I have done some comparisons with CPm 154. Hi heat at 1980, forced air quench and LN2, temper at 975 3 times for 2 hours. Result is RC62. The same above but with leaving out the cryo and I still see RC 62. The Crucible Data sheet for 154CM cautions against the higher heat temper, saying loss of corrosion resistance and some toughness. I have not been able to detect this differnce even with a thin grind fillet knife and using in and around salt water. Cutting tests on rope seem to show equal edge holding. My conclusion is that the differnce is small and not a concern for a knife blade, at least for this steel grade. The CPM structure is more forgiving than the original 154. I still use the LN2 cycle just for quality control and to be consistent. Would like to hear if anyone else has a seen a noticeable differnce.. Phil
 
Dunking it in LN2 is not the same as using a deep cryo -200C chamber with computer controlled ramp rates for managing how fast the temps change.

Doing a hardness test on these techniques is not going to clearly show the changes. I recommend sending your blade tests for metallographic analysis so that you get a retained austenite test result amongst other things.

A reduction in retained austenite has been studied in lots of tool steel papers. What they show is:

* Better machinability in the hardened state
* Higher toughness
* Increased adhesive wear resistance

All of these mechanical properties can be objectively and repeatably measured.

However, there is other heat treating techniques that will also reduce retained austenite.
 
It is interesting to see that nobody reads the research. All of you seem to be focusing on retained austenite. If the only thing that cryo does is convert retained austentite to martensite is true, why did the US Postal Service get tremendous results on brake rotors. They paid for tests that were done by Greening Labs. The cryoed rotor got seven times the life. By the way, rotors are J431 G3000 cast iron. If you cross section them you find a PEARLITIC structure with no austenite. Why did NASA find affects on aluminum? Why did Linde find affects on copper?

Nate, your opinion about cryo is just that, and it is a misinformed one at that. The research proves you dead wrong. I have the tests on golf clubs that were done with a mechanical hitter by a laboratory. They got six to twelve yards increase. I've done many tests on racing car parts. The cars are faster, especially when you treat the suspension members. And the last time I looked, the fastest car is the one that goes the distance of the race in the shortest time. If you don't finish, you were not fast, and cryo increases the reliability of many car parts. I'd like to see your research on rifle barrels, we find that they are more accurate. These things are not just in people's heads. They are proven by research. Or did the cryo guys somehow get NASA, IIT, University of Trento, Purdue University, Los Alamos National Laboratories and others to lie in their research so that they could profit???? People who make irresponsible statements are the ones who hold technology back.

Basic metallurgy will tell you that there are other affects than just the retained austenite to martensite conversion. Of course, you have to do it right. Phil, dunking a blade in LN2 is like water quenching D2. If you go down to quickly, you not only induce cracks, you miss some of the better happenings in a cryogenic process. You see, a lot of things are going on in metal (not only steel) as the temperature drops, but they do not happen if you go too quickly. For instance, the amount of carbides that form depend on the soak time at -300F.

As far as when to do it, yes it is best to do after a snap temper. You all seem to be concentrating on reduction of retained austenite as if it is a holy grail of some sort. Look to the other things that cryo does and you will get more benefit. For instance, the formation of very fine carbides is great for wear resistance. The reduction of vacancies also helps. The reduction of residual stresses are important as is the redistribution of alloying elements.

By the way, if you are looking for a reliable cryo company in Northern California, look up Victor Aviation in Palo Alto.
 
warbird436:
Could you perhaps venture any thoughts on why the CSA has so few recent additions to the academic article database? It seems it is still populated only by the same few old papers that are invariably cited.
I would think a technology with so much claimed potential would certainly draw a great deal of academic interest.
 
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