So, since reading and watching Jay Fishers extensive chat/piece on Heat-treating plus Cryo-treating knives to get the uttermost out of all steels (this includes carbon steels, and not strictly limited to modern stainless and tool steels Jay talks about), I started researching Cryogenic Processors. This is the model from National Cryogenics Cooperation that was purposely built for knifemakers in mind https://www.nationalcryogenics.com/equipment/standard-line-machines/all-new-ltk-27/ Here are the details of the quote I received back: Pricing in USD Base Model $6,470. Then the list of add on's/ upgrades 1 Maglock lock out - Locks machine while it is in use. Included. 2 Emergency Stop – Note that there is an E-stop on the HMI already. This is for a physical Emergency Stop $75 3 Stainless Steel inner-chamber $170 4 4' LN2 transfer hose. Included in base price 5 Insulated 4' LN2 transfer hose $105 (this seems like a must for Liquid Nitrogen) 6 6’ LN2 transfer hose. $105 7 Insulated 6' LN2 transfer hose. $255 8 Custom length transfer hose/s TBD 9 Remote viewing/operating capable $575 10 Data Logging $675 As you will see here the cost is most definitely surpassing the expense of a grinder and a heat-treat oven as the most expensive pieces of equipment a modern knife maker needs (that is of course if you wish to go this route, I do, Jay's stuff has left quite an impression on me!). I have reached out to a person from Nation Cryogenics Equipment because there are models like the LTI-12 that have a supplemental heat option to help bring the blades back to ambient temperature. This was left off the knifemakers model (scratching my head), not sure what knife makers they spoke too...but such an insulated box would take forever to get back to ambient by itself! We don't all have the patience of a saint! Another model is the LTI-40 which not only has the capability of heating the blades to ambient temp, but also reaching 500F so you can temper as well without ever having to remove the blades! The base price on that model is $8150 US and to have the tempering heat upgrade it's another $3700, then the rest of the upgrades such as hoses etc. are pretty much as above. https://www.nationalcryogenics.com/equipment/standard-line-machines/machine-options/ That's the page for those two models. You will notice the LTI-12 is has much smaller internal dimensions that the LTK-27 Hope this was of interest to those on the forum, even if they have no intention of pursuing a Cryogenic prosessor. Cheers Griff
A dewar is most commonly used for the liquid nitrogen although you can ad in a Liquid Nitrogen Withdrawal System if you want. This can get you into the process without a second mortgage then you can go up from there if you want.
@John Noon I totally missed your response somehow considering I am on here a lot! Lol! John I understand what you are saying, it's just I am getting caught up in the theory that unless you have a controlled decent of 4-5 degrees per minute to deep cryogenic temperature (below -300F) you risk micro fractures from shocking the steel by just dunking knives into LN2. Maybe you can go from ambient to fridge freezer-to dry ice-to dewar/LN2 as a more cost effective treatment? Or are there dewars with such control?
You would fill a foam container or camping cooler with the LN2 and place the knives in a fryer type basket hanging above the LN2 with lid on the cooler they will get very cold gradually and after a couple hours you can submerge the knives.
Post revival, some accidental research and the 4-6 degree temperature drop per minute looks to be very important parameter to control. Just dunking in liquid nitrogen then removing after a few minutes does not work properly. Also found some research that suggests some materials need only to reach the -100 or -300 range with no soak time while some materials need up to 40 hours at temperature. I am in the process of getting a build list put together for a do-it-yourself package. With the interface already programmed for common materials. Best part is with a controller you can have any temperature and soak time needed to get below the Martensite Finish temperature.
Thanks John. Jay Fisher definitely isn’t full of when he talks about controlled temperature decent with cryogenic processors like the one I posted about that started this thread. I think I will avoid it all together by treating -like many- my AEB-L and 440C without cryo and foregoing what extra RC point I squeeze out of it, or even easier, just purchasing the Sandvik stainless steels in future, which by the manufacturers recommendation you only need to deep freeze below room temperature in a regular old freezer or dry ice. Look Jay’s whole thing is he sells his knives to the real deal special forces etc. around the world, and so yes, he needs to get the utter most out of his steel to saddle up right next to his reputation. Is one of my 440C kitchen knives ever going to be tested like one of Jay’s special forces purposely made tactical blades, I hope not, that would have to be one Killer Tomato, lmfao! Cheers, Griff
The datasheet for AEB-L (13C26) recommends -70°C for optional cryo treatment. Almost a Prairie cold snap. Stick em in the snow overnight in February. LOL Although I am intrigued by the idea of complete Martensite conversion, I am also aware of the law of diminishing returns. So I pop my blades in the freezer between tempering cycles. OK, it's not going to help a huge amount, but the cost to me is near zero. I guess as long as customers are ok with that, I am too.
With AEB-L I had a blade going through second trip in the furnace. It as scrap so I did not mind messing it up. I stood outside at -35C and slowly flexed the blade until it reached outside temperature and stopped flexing. Even a freezer makes a difference if taken from air quench then placed in the freezer until frozen.
You're a brave man John! I had one Nitro-V blade where the heat treat didn't stick. I have no idea why. After tempering I could bend the steel and it wouldn't return to shape. I had three other blades in the oven at the same time, one AEB-L, one 154CM and one S35VN and these all came out nice and hard. I ended up sticking the Nitro-V back in for another go. Is there something in Nitro-V that makes it need cryo? I was told to heat treat the same as I do AEB-L. Dan
I had the same thing happen with AEB-L on a couple of occasions. A similar material spec sheet recommends getting to below zero within 30 minutes for best results. The martensite finish temperature is around 0C from the looks of it
I've made a handful of knives out of Nitro-V before I got LN2 and they all hardened, but I noticed a pretty big difference when I started putting my knives in cryo overnight. Both with abrasion resistance and edge retention. I also noticed that my knives became more magnetic out of cryo than if I only plate quench and I believe that is because austentite isn't magnetic but I'm not 100% sure on that... maybe someone else can confirm that.
I can’t think of the exact mechanics at the moment to explain it but a harden material will have a stronger attraction to a magnet. Even a non magnetic material or weakly magnetic like some stainless steels when work hardened will be more magnetic. It is related to the strain the material is under when quenched, machined or bent
Caveat: I am not a metallurgist by any stretch, but I did study electronics, in which we covered some magnetic theory in conductors and transformers. I am not sure that the small change in Austenite to Martensite when cryo treating the knife would make a noticeable difference in how magnetic or magnetically permeable it is. The increase in magnetic properties is probably caused by improving the alignment of the magnetic domains within the steel from the cyro treatment. Basically all the tiny magnets within the steel get lined up going North and South making the steel more magnetic. Similar to stroking a magnet on steel repeatedly in the same direction forces these tiny magnets to line up, thus making the steel more magnetic. Conversely, a degaussing device applies a strong magnetic field to randomly scramble the tiny magnets and make the steel appear less magnetic. During work hardening, some Austenite is broken down to Martensite. Martensite is ferromagnetic. You can observe this conversion effect when drilling 304 stainless with a less than sharp drill bit. After burning it for a while the swarf starts to cling to the 304, which is normally non-magnetic. https://www.bssa.org.uk/topics.php?article=122 Dan
