cryo? where and how to handle liquid nitrogen?

Will52100

Will52100

Joined
Dec 4, 2001
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I keep debating on getting a heat treat oven, mainly over the cryo part of it. How do you handle liquid nitrogen and where do you get it? I've got access to an old 30 day tank, probably won't hold nitrogen more than a day or two though. Used to use it for artificial insimination, so don't know if that's the best tank for knives or not. I've heard of using thermos, but it's kinda small for anything other than folders. I generaly don't do a stainless bigger than about 12" overall, blade and handle.

I checked a local, 45 minites away, welding shop and they said they could fill a thermos. Don't know if they will still do it, it was a couple years ago.

Suggestions?

Thanks
 
Don't let the cryo keep you from getting an oven, as many steels can be successfully treated without cryo. It's just that some steels can really benefit from the deep freeze.

As for LN handling, I picked up a used dewar from this site a few years back. It's an 8 week dewar and holds somewhere around 32 liters. Keep an eye to ebay as well. I'm leary of handling LN in anything but a dewar, but a good thermos could work for a small amount. You know this I'm sure, but you CANNOT!!! use anything sealed to carry LN. It WILL gas off and the pressure will build causing the container to explode, no matter the strength, spraying -321F liquid all over the place.

Also, it's a good idea to never carry LN in the car with you. Use or borrow a pickup if possible. Not only does the LN gas off and displace oxygen over time, I'd hate to think of what would happen if you had an accident with a container of LN sitting next to you.

Like I said, best bet is to keep an eye out and find a decent used dewar. As long as the neck is wide enough and the tank deep enough, it should work.

--nathan
 
I think the artificial insemination tanks are called dewars. I have a fairly large tank and my LN costs about 90 bucks to fill. It will last about 3 months. The LN is useful for the HT of steels like 52100, A2, D2 and other stainless steels. For the steels just mentioned the wear resistance is increased by as much as 500%(A2). I have text books with the technical data if your curious.
 
my dewer is a 10L and it last about a month the mouth is 2and an 1/8 wide so any big stuff i haveot pour to cool in a cooler

but get the kiln even is your not ready to go cryo
often time s i wish for a bigger mouth but you know what i have made it this long ( 4 years )
cost to fill 27$ and i only fill when i know i ll be runninga pile of steel in HT
that way it does not jsut evaporate

might also party a bit with the little left overs now and then ( makes beer cold fast )
 
Thanks, I'll check the old dewar out and see if it's still good enough, would prefere a 90 day tank though. I'll see what I can find.
 
if i remeber riggt the day ratings are for non use cold and you will sure boil off LN fast even with roomm temp blades as they cool to -300
 
True, most of my experiance with cryo comes from AI, but a 90 day tank should last for a couple days of blade treatment. Anytime you take the top off it evaporates faster.
 
Where would you suggest getting a dewer from? I've been looking online and the suckers are expensive!
 
You can get on a route to get filled every 90 days. They come around and fill my tank every three months. Always put the tank on a piece of wood or rubber floor mat if its setting on the concrete it will empty faster.
 
When my father was dairying we were on a rout, he had a 60 day tank. I don't do enougb stainless to worry about that. What I'd like is to be able to heat treat 4 or 5 blades once in a while. That means I need to be able to run up to town and get enough for 2-3 days worth.

I've been looking on ebay, what would you suggest, a 5 litter, or better off with the 10 litter?

Thanks
 
My 10 liter will go a month with about 4-5 batches of blades in that time. I do try to keep it upright in a freezer though $25 to fill it.
Ken.
 
the 10l works great for me but that said i can get LN jsut a few miles from the house
i fill wuse a few times then if i make it in time get some small work out of it at the end of the month
other wise i jsut get a pile of blades ready then have it filled
i try to avg 20 or more blades per fill jsut so i can avg 1-2$ a blade in LN cost
 
I'm going to have to second what nathan said. You can't store LN sealed. Regardless of the insulation that it is stored in, there is no way on God's green Earth [literally] that you can keep something at or below 320F for an extended period of time, so expansion is inevitable. I work with LN and LOX on the C-17, and bleed/drain valves are always emphasized on the LOX carts. We use LN mostly for training because of its inert properties (doesn't react with grease).
 
Not to hijack too much but is it possible to do cryo with dry ice? If so would that work for the amount of use you'll need it for? That's something that can usually be found fairly easy and easy to deal with.
 
Thanks, I'll keep my eyes open for a 10L,

I've thought about dry ice, but from what I understand it doesn't get quite cold enough and then there's messing with acetone or kerosean. Also there's no place local that fools with it.
 
Mike Quesenberry said:
For the steels just mentioned the wear resistance is increased by as much as 500%(A2). I have text books with the technical data if your curious.
Click to expand...

I'm VERY curious. 500% increase in wear resistance just from cryo-treatment is so incredible as to be difficult to believe, with all due respect.

Are we talking two blades of exact dimensions, ground the same, quenched and tempered the same, tested exactly the same way? Are we talking about polishing the surface of a cylinder, or sharpening an actual knife edge? Are we discussing a race that rides against a similarly-polished, well-lubricated bearing, or an edge that cuts through cardboard held against a hardened steel impression roll?

I'm not trying to be a pain in the backside, just honestly interested in the testing involved.
 
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