Appropriate Cryo Methods

I have a LN cylinder and I used LN for years until the supply became unreliable here.

I've always tested my steel in my shop after HT, temper, and cryo before and after using my Rockwell hardness tester..

I've been simply sandwiching my steel inside a styrofoam ice box between 2 blocks of dry ice overnight for the last several years.

I test after the flash temper, record the result, then do the dry ice thing overnight. The next day I temper twice again for 2 hrs. each time.

There is no discernable difference in the results of using either method, ie: Ln versus dry ice. Both give me a rise of 1 or 2 points in Rockwell C hardness.

Now, who would like to buy my LN cylinder?? It keeps the LN for several days in the liquid state and can be used over and over until it runs dry.
 
I just re-read Art's post.

He reminded me that after cryo you must re-test the hardness and raise the next tempering temperature to suit. I test before, between and after cryo and always need to raise the next tempering temperature to suit in order to bring the hardness down to working hardness again.

What more proof do you need that cryo works?

I would never sell one of my knives without cryo.
 
Don Robinson said:
Now, who would like to buy my LN cylinder?? It keeps the LN for several days in the liquid state and can be used over and over until it runs dry.
Click to expand...

Don, it's been years since I used any dry ice, because it just disappears too fast but my results with liquid nitrogen pretty much mirror yours. The comment about your dewar got my attention though. If it only holds for a few days, it has likely lost its charge (vacuum). My old cryo tank gets me through about 5 weeks of HT on 20 litres and my newer one closer to ten weeks on 34L. It's really the only reason I use LN over dry ice.

Rob!
 
This is a great thread, I'm going to start using CPM-154 in a week or two and have been researching the heat treatment.I have my own heat treat oven but I only make knives part time and did'nt want to have to invest in quantity's of LN and a dewar. looking at CPM's data sheet, dry ice is a an acceptable cold treatment. so, researching the dry ice procedure I've read differant methods,blocks and slurry's, acetone or kerosene. right now I think I've settled on the kerosene slurry, my question here is will the temp be much differant using a slurry mix verses putting the blade between blocks. also being this cold what kind of container do I put this mix in, does it matter if it's metal or plastic or foam?
 
My worry about putting the blade between blocks of dry ice would be heat conduction which you be better and more even in a liquid medium.

Doug
 
Doug Lester, sorry . It is ATS34

Don , I also have a RC hardness tester . I also do about three checks on each knife .
 
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I break the dry ice into about 3"X 2" squares so I can get it in my 3L double wall stainless steel coffee pot . Put the knives ( I usely only do 5 knives at a time ) in it and pour in the acetone. Most of my knives are under 10" so I can close the lid and I put the coffee pot in a plastic cooler with fiber glass insulation around the coffee pot and put the top on the plastic cooler . And leave the knives in over night . I'd like to have a thermonater to check how cold it is .. And like I said earler the knives come out harder than when I was using LN , and would like to know why because the LN is colder. . And I'm using ATS34 I'm about out of it so I'll be going to CPM154CM with my next steel buy.
 
Doug,
I would think you get the dry ice colder by making it a liquid medium and the temp would be more even on the blades . From what I'v read the dry ice only gets a little over -125 with acetone and the LN -250 , some people say LN gets -300 but I don't think it gets that cold is small amounts.
 
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hey I don't have links for the cryo files I have or I would post them- if want to PM me your email I can send to you. Is there a way to post files here without links?
 
If any of you live near a dairy farm and want LN they should have a supplier that stops buy to refill their tanks that they use for their artificial insemination program.
 
Ausbrooks said:
hey I don't have links for the cryo files I have or I would post them- if want to PM me your email I can send to you. Is there a way to post files here without links?
Click to expand...

yes, send the files to me and I will get them posted -- if they are OK to post.
 
Art, I've been using CPM154 ever since it came on the market. ATS 34 or 440C before that.

Expect the same results, 1 or 2 hardness points higher after cryo.

Yu'll like using CPM154. I buy it in large sheets.
 
I don't know if it has been covered as I am just now finding this thread. The biggest roadblock for me and Cryo-ing has been that the welding shops will ONLY put it in an APPROVED container, which means a DEWAR. Dewar's are expensive, I watched them on eBay for a month a few years ago and never found anything that would work for less than $400! Please, don't get me wrong here, I'm not saying they can't be bought for cheaper because I know they can be, if you're in the right place at the right time with the right amount of CASH! I could have bought a NICE one that would have worked, it was set-up to hold semen straws used for artificial insemination on Show Goats...yes, I said show goats, I did other things in my passed life, anyway, it would have worked, OK at best, the price was 225.00, which was the "Good Buddy Price", that was years before I was making knives. We were going to start buying semen and needed a place to store it. We ended up passing on that one, and never found one that we could afford. Keep an eye on eBay and probably Craig's List and for those that live in Texas, and other areas of the country that have a lot of livestock production, cows, goats sheep, etc., look into the AG sites where they will have a 'Classified' listing. Bigger producers will usually have several of them, more than 2 or 3 and will eventually either upgrade in size and sometimes downgrade in size as well and will want to sell their older one. Also, in places like Texas and Wisconsin where livestock breeding programs are huge, there may be AG Auctions where they will be retiring (preferably) and sell out everything.
BTW, if BOSS can't get the links posted, I would appreciate being added to the list for the Crying research info. I did get go back and read some of the posts, I'll send Ausbrooks a PM.
THANKS, Rex
BTW, when this subject was discussed before, it was pretty much short down almost before it got off the ground, I can't remember exactly why it went like that, maybe because there was no evidence that it was beneficial in high carbon steel...I think.
 
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So what is the informed consensus concerning carbon steels and cryo? If its better to manage RA during the heat treating before the quench and RA is at a minimum is it really worth the cost and trouble to maybe get a point more in hardness? Just standing on the outside looking in it seems like it is not as long as one is indeed limiting RA in the first place.

Is there a benefit to putting more carbon into solution and having to deal with excess RA conversion through cryo than limiting the amount and having the blade gain in hardness due to lack of RA?
 
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