Will 0-1 benifit from Cryo

blgoode

blgoode

Knifemaker / Craftsman / Service Provider
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Oct 3, 2003
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I have a customer that is interested in having his 0-1 knife(made by me) cryo teated. Is there any benifit to the 0-1? I have heard that 0-1 will not benifit greatly so should I stear him otherwise if this is the case.

Also would I get the blade to the point where I am ready to glue up the handles then send off to cryo?

Blade will be around 11" long.

Thanks
 
Mete will chime in here,I'm sure.There is no advantage to cryo on O-1,There should be very little unconverted Austenite,thus no gain to speak of.
SA
 
One bit of data shows retained austenite dropping from 8.5 to 5.5% retained austenite after cryo. This was hardened from 1450F. While I always say cryo REDUCES retained austenite I wonder if you makers are thinking it eliminates it ? In any case cryo does help with O-1 but not overheating it is just as important to keep the amount down. So 1450F for 10 minutes ,quench, cryo immediately [is you snap temper do it at 300-325F] then double temper at 400F. There is a toughness peak at 400F for O-1 which drops off considerably at 500-600F.
 
mete said:
There is a toughness peak at 400F for O-1 which drops off considerably at 500-600F.
Click to expand...


Doesnt this temp range cause embrittlement on all steels for some mystical reason mete?
 
blgoode said:
I have a customer that is interested in having his 0-1 knife(made by me) cryo teated.
Click to expand...

There's your answer, right there. Your customer wants it done, and obviously believes it will help make a better blade(I think so too, but that's irrelevent), so you should get it done.
 
True....I just didnt want him waisting his money.
 
What ever Mete says is gospel to me but aside from that - (O1) yes Brian it does; and it does well enough to insist upon doing it whenever equipment permits. I, for our thicknesses up to about 1/4 inch prefer soaking at 1475 F / 9 minutes. Oil quench (I no longer interrupt quench O1 because I had but lost the touch) until below about 150 F and snap temper in preheated ~325 F / 1 hour. Cool to room temp and deep cryo minimum 12 hours (10 should do as well). Warm to room temp and place in 400 F temper / minimum 1 hour. Repeat at ~25 F less than primary temper / minimum 1 hour. Please be aware the most important variable in time I have found here for O1 is the soak time. I find 9 minutes works well and less, even 8 minutes, does not. At the same time remember over soaking too much is not good either. For O1 in the thicknesses we use I think I like 9 minutes for the soak. It is also very good to do the preheat for about 7 minutes before ramping to austenitizing. That is my basic opinions on O1.

RL
 
Thanks Guys - RLinger - So I should HT snap temper - Send off to Cryo - then finish the tempering cycles as I normally would?
 
No. Remember please that I recommended if equipment permits. You should not send away for cryo unless you are walking over to the next door neighbor's house. YES, it can work as long as you snap temper properly first but not at all optimal to ship off for cryo. I believe myself correct in saying this. If you can not cryo in-house my suggestion is not to include it within your heat treat. Anyhow put your O1 , or any steel, through a pre-heat and ramp as quickly as possible to austenitizing / soak and quench quickly and uniformly. Place in pre-heated temper before falling below ~125 F if not high alloy. Do not be overly concerned though about your O1 properly heat treated without a cryo treatment. Done well it will perform well. Let me look my notes up on preheat for O1. I am thinking 1200 F for about 7 minutes. I'll be back in a sec.. I'm back. Yep, 1200 for about 7 minutes. Don't go much at all more than that but it is good to ramp the steel moderately to that temperature. After preheat has expired go as fast as equipment permits to austenitizing. I like 1475 F for O1.

RL
 
Thanks RL - That helped me ALOT! :D

What about the poor mans Cryo in the freezer?
 
Yes. Do you have a few years to wait on it? There is more than one term for marketing cryo treatment of steel. One very catchy phrase that I really do like is 'aging'. I love that marketing term. It just says it in a way that makes you think it worth purchasing. It is based in truth. Your cryogenic treatment (house hold freezers do not acheive cryogenic temperature) speeds, in a marketing sense, the aging of the steel. Your freezer will speed things up too but not at cryogenic rate. In theory you can leave your blade lay at room temperature for a very long period and the same will result - within arguable reason. To do it correctly and effieciently a temperature of less than -100 F is required; my opinion. Dry ice is a good try but I find it difficult to mix a solution with dry ice, in order to uniformly cryo the steel under cryo, and retain a temperature low enough for long enough. My advise is bite the bullet and buy a GOOD dewar.

RL
 
Brian,

What type oil are you quenching O1 in? I can't get a handle on interrupted quench with the Tough-Quench I use now. If you are using off the shelf dollar a quart vegitable oil I can give you a killer interrupted O1 quench that will work. I am having difficulty learning interrupted quench with what I now use. O1 is a steel that loves interrupted quench and since you, reasonably so, love O1 so well I think it good you know all I was taught about it. Tim Zowada taught me what I first learned of heat treating it.

RL
 
roger I'd think
if you preheat the oil to 125 min that alone would give you a controlled
interrupted quench in any oil you're using. ?

they even use cryo on cast iron cylinders Harley's done it for years.
even the plastic top handles on Stihl chain saws have it done to them.
so for the big wigs to do it there has to be a reason they won't waste
their money by any means..
I even take chain saw files new out of the box and cryo them if I have
n2 left.. ;)
 
RL - I am using peanut oil heated between 125 and 140 or so. Send me what your talking about. What exactly is interupted quenching?

Dan- Thats food for thought....glad you chimed in.
 
Dan Gray said:
roger I'd think
if you preheat the oil to 125 min that alone would give you a controlled
interrupted quench in any oil you're using. ?...
Click to expand...

In a word.. no. Interrupting an oil quench is us bladesmiths version of martempering/marquenching. I don't do it with O1 anymore because I have the salts and can do the real deal, but I do use this method on shallow hardening steels like W2, 1080, 1095 etc... It takes time a practice to nail it right, as the quench time will change for each steel and cross-section and the type of oil makes a HUGE difference in time. Industry would probably call it a timed quenched.

The idea behind it all, and the benefits of it, is to let the entire cross section equalize in temperature before commmencing with martensite transformation. This allows a more even transformation and cuts way down on stress and distortion. The other very significant benefit is the autotempering effect it has. since you are descending through the martensite zone very slowly, in the insulating environment of air, a significant percentage of the matensite formed will be subjected to tempertures in excess of 250F. thus converting it to more stable beta martensite (Body centered cubic instead of body centered tetragonal). If you see what affect this can have on habit plane/plate inpingement on the microscopic scale, it becomes very desireable. To simplify things, what it does is gives you the quench and half of a snap temper all in one shot ;) .

If you rely on the 120-150F oil alone to do the trick you will be below 250F before any benefits can be gained. the trick is to know when to interrupt in order to get it as close to Ms without going under. Like I said- It takes time and practice.
 
Brian, interrupted quench is just as it seems to be. Let me tell you what I know of O1. Listen and print this off for your records (since you are becomming a premier O1 maker) learn to quench your O1 to about 350 F. At that point in steel temperature you will still air cool to about 125 F and then IMMMEDIATELY place in preheated temper. You must quench quickly, just as you other wise would any steel, but learn to be able to pull at about 350 F. Some oils are easier to teach you this because of flash point. Some are not. You need to practice it and learn. Learn when to pull at about 350 F, a little less perhaps but not more. I can give you a bench mark. With vegi oil preheated to about 125 F quench the blade and cut the oil with the blade, as you would within any quenchant, while counting to seven seconds. Pull and if flames submrge immediately for another second. If no flames do NOT submerge but hold in still air until ready for temper (approx. 125 F). Place in preheated temper immediately and ABSOLUTELY before steel falls below about 125 F but AFTER it falls below 150 F.

In quenching with vegi oil you want to look for smoke but no flames. Your constant in quench time will be about 7 seconds for a 1/8th inch thick spine. Thicker steel will increase quench time. In vegi oil you are looking for smoke from the blade but no flaming. 350 F or a bit less is your target for pulling from quench.

You learn to do that and you temper at 400 F and then at about 375 F you will have a killer blade. (don't forget the preheat prior to austenitizing if equipment permits)

RL
 
I think I missunderstood interrupted quench


interrupted quench = banite tempering ?? :confused:
 
Roger I am not doubting your results at all, it sounds like you have had great success, but your method emphasizes a great concern for not letting the blade cool completely before tempering. I totally understand the concern for stress and distortion in an O1 blade, quenched from austenitizing all the way to room temperature, and it is true that tempering should follow Mf ASAP, but I guess I am not following the advantages of rushing a blade to temper that may still have 2 or 3% more martensite to convert. Granted you will probably get the conversion and then zap it on a second temper, but is there a grave consequence that I have yet to experience in letting a martempered blade reach room temperature? Although if this is the way Tim Z. showed you, he will probably not hesitate to point out my ignorance the next time we do a heat treat together.
 
Dan Gray said:
I think I missunderstood interrupted quench


interrupted quench = banite tempering ?? :confused:
Click to expand...

No, bainite is made in austempering operations. These involve quenching fast enough to avoid othe structures and the arresting the cooling and holding the steel at a temperature above Ms (400F.-500F for many steels we use) until the conversion to bainite is complete. If you let thigns drop below Ms you will instantly start forming martensite and one could not accurately call that austempering. This operation is beyond the abilities of interrupted oil quenching and really needs realiable temperature controls like waht you get in molten salts.
 
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