Liquid Nitrogen for Cryo Treatments- larger projects and container solutions

E

Eeey_Yo_Mikey

Joined
Dec 9, 2019
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14
Hello all!

I have been using liquid nitrogen during my heat treat regiment and I normally utilize a dewar, and simply place the blade in the dewar having it suspended by some stainless steel wire.

I am beginning to run into an issue however with larger blades that are either too wide for the dewar mouth or simply won't fit (hatchet/cleaver/etc).

My usual soak times are 8 hours and I am curious if I were to get a stainless steel box or container I can pour off some liquid nitrogen into the container and place the blade/hatchet laying it flat on the bottom of the container. I do not grind my knife pre-heat treat (thicknesses ranging from 3/32, 1/8, and 5/32) using s35vn.

Im definitely open to suggestions though on how best to accomplish this.

Thanks!
 
My dewar has a 2" opening, so it handles most of my knives. For cleavers and other pieces that won't fit, I lower the austenitizing temps a bit and use dry ice slurry. I figure, for a cleaver especially, a point or three extra retained austenite won't hurt a thing.
 
my 20L hahs a 3.75" mouth cause most of my kitchen knives are over 2 inch tall for the 4 inch tall veg cleavers i have some foam insulation that i carved a section oversized to the cleaver spec and glued together. i slip the cleaver into the foam and then pour the LN in on top of it (i time cleaver HT for when the tank is just about empty and just uses it all up
 
I have heard of people using a small ice chest as the container to pout LN into for larger blades. They place a foil pan in the bottom and pour in a little LN. After a little while to allow things to cool down, they set the blade in it, then pour in enough LN to cover the blade fully. Depending on the length of cryo, I guess you will have to add more occasionally.
 
There are dewars with 5" necks, if that is an option. Evaporation rate goes up significantly though.
 
Yeah a small styrofoam ice chest is used when we freeze brand out horses. The brand is five inches tall. I would agree with Stacy that you are probably gonna need to add more for a long cryo. They don't seal real great.
 
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