Short term liquid nitrogen storage

Matt Rochester

Matt Rochester

Joined
Nov 28, 2014
Messages
1,864
Hey guys, been a while since I’ve been on here but I have a quick question. I have a guy wanting a filet knife out of AEBL. I have mostly been sending out for heat treat for AEBL since I don’t have a dewar. Seems most turnaround times are 3-8 weeks currently so I figured I’d just do the heat treat on 6 at one time. They are roughly 14” long. My question is, is it possible to use something for short term storage instead of buying a dewar? I’m talking like a 15 min ride home and one cryo soak. So total of 2 hrs. We have a guy in town that makes ice cream with LN2 so I can get some from him. I don’t have a need to keep it long term. Is this a waste of time or should I just buy a dewar? Thanks in advance!
 
I have used freezer, dry ice, and LN for AEB-L. I agree LN is better than either. Since your friend has the LN, could you take the blade to his place for the LN treatment? It would be ok to keep the blade clamped between bars from quench to his place if it's only an hr there.

I suspect you could pour the LN from his dewar to a cooler large enough to hold the blades and bring it home. Wouldn't expect the LN to keep for days that way, but a few hrs should be good. 30 minutes is long enough for blade in LN to work just fine. I normally leave blades in LN for an hour or so.

Depending on his cost for LN the matter of waste might or might not be important.
 
Bring something that the blades fit in to the ice cream place. A small oven pan or something. Pour LN2 on them, out in the parking lot or where ever. No soak time is required with the ln2. Throw out the ln2 left overs and go home and temper.
 
Ken H> said:
I have used freezer, dry ice, and LN for AEB-L. I agree LN is better than either. Since your friend has the LN, could you take the blade to his place for the LN treatment? It would be ok to keep the blade clamped between bars from quench to his place if it's only an hr there.

I suspect you could pour the LN from his dewar to a cooler large enough to hold the blades and bring it home. Wouldn't expect the LN to keep for days that way, but a few hrs should be good. 30 minutes is long enough for blade in LN to work just fine. I normally leave blades in LN for an hour or so.

Depending on his cost for LN the matter of waste might or might not be important.
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Being it’s a restaurant type place I’m not sure if he could get in trouble or not from me sticking knives down in the dewar?
 
Put your knives in a styro cooler and pour some LN on top, SLOWLY and CAREFULLY. Faceshield, gloves, long sleeves. It'll boil vigorously as it removes heat but subsides quickly. Small additions at first...

That said, what DeadboxHero DeadboxHero said. It is best if the quench is as continuous a curve as possible from Aus temp down to lowest temp achieved. Discontinuity down at the low end stabilizes austenite (undesirable).
 
If you're planning lots of blades, then buying a dewar is by far the best bet. BUT - if this is a 1 time operation then it might work trying some temporary method.
 
For about $30 buy a 1-gallon stainless steel vacuum bottle on Amazon.
When you turn the oven on to pre-heat, go get it filled with LN at your buddy's Ice Cream store. 2 liters, which is half full, should be plenty.
Do the HT and after the plate quench put the blades in ice cubes for a minute to drop the temp down, then put immediately in the LN.
Depending on blade length, you may be able to put them in the vacuum bottle. If not, put the blades in a small Styrofoam cooler and pour the LN over them.

Just to be safe, I would transport the LN filled vacuum bottle in a 5-gallon drywall bucket padded with bubble wrap.

1 Gallon Water Jug Stainless Steel Double Wall Vacuum-Sealed Hot & Cool
 
Stacy has the right idea if you don't need a dewar - do a search on this Amazon #B0BB5W6QKP for $32 shipped. You'll be able to do well more than 2 blades with each fill.
 
Hmmmm...I wonder if the university I work at will sell me liquid nitrogen? With those 1 gallon containers, that would probably do a batch for me!
 
I use 3l thermos with glass inside, I guess it is the same beforementioned gallon item, just another make/model. I buy 2kg LN for 6 euro, I can do heat treat second day, no need to hurry. Batch of 5-7 knives easily, I think I always use less than pour away after. But, as a hobby maker with less than 25-30 knives a year I don't see myself buying dewar.
 
Thanks guys. Should I clamp all the blades together in the LN2 to help minimize warp? They are all the same pattern. These have not been ground, only profiled and are .100” thick, 14” long.
 
It should not matter. Clamping will be fine, though. The LN will drop the temp regardless of the total thickness.
Since you won't be storing the LN afterwards, I would put the clamped blades in the bottom of a small foam cooler and pour half the LN over them. When it is partly evaporated, add the rest. Leave them until all the LN has evaporated. Then temper as normal. You can temper while clamped, aswell.
 
A Dewar is not a bad tool to have. The liability for anyone to allow you to take LN2 off premises in anything less is steep. The safest way is not having to risk extra steps while handling it. An accident will be harder on you bank account than a $300 Dewar.
 
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