Liquid Nitrogen use and storage

Bill Coye

Bill Coye

Knife Maker
Okay, I've done the dry ice/acetone cryogenic treatment on my first knives.

Although the dry ice trick is inexpensive, we know liquid nitrogen will get those blades colder.

Does anyone here cryo their own knives with liquid nitrogen? If so, what's the skinny?

Storage: is a lab-grade dewar appropriate?

Treatment: I've read 8 hours.

Thanks Dogs!

BC
 
I cryo mine. I bought a 20L dewar. I have to fill it about 3 times a year. It cost me about $25 each time. I leave my blades in overnight ( at least 8 hrs.) If you plan to heat treat your own blades I think it is a good idea. It's not the same process that the profession heat treaters use, but I think it is good.
-John
 
Bill Coye said:
Okay, I've done the dry ice/acetone cryogenic treatment on my first knives.

Although the dry ice trick is inexpensive, we know liquid nitrogen will get those blades colder.

Does anyone here cryo their own knives with liquid nitrogen? If so, what's the skinny?

Storage: is a lab-grade dewar appropriate?

Treatment: I've read 8 hours.

Thanks Dogs!

BC
Click to expand...

John Barker said:
I cryo mine. I bought a 20L dewar. I have to fill it about 3 times a year. It cost me about $25 each time. I leave my blades in overnight ( at least 8 hrs.) If you plan to heat treat your own blades I think it is a good idea. It's not the same process that the profession heat treaters use, but I think it is good.
-John
Click to expand...

Could this be explained or could you point me in the right direction. And could one of you post pics? What are the benefits of doing it this way?
 
Bill I do 6 hours on mine. What I use is a semen dewar. I kept my eye out for one of the dairy farms going out of business and got mine. Check out some of the services in the yellow pages or check out your local welding suppy for nitrogen.
 
I have a 30 liter semen dewar I bought used on ebay. Dewars are on there all the time.
Buying them new is insanely expensive.
A 30 liter is too big. A 20liter is fine and a 10 liter for the occasional guy might be perfect.

My 30 liter will last 4 weeks in the summer and 6 weeks in the winter before it boils off. I made a large rolling insulated box to hold the dewar in and that gave me a couple more weeks.

Filling my 30L costs around $65 to $75 depending on who is staffing the counter that day.

For those that don't know, any one can buy liquid nitrogen. It is not at all regulated and nearly every welding gas supply place has it. The stuff is a by product of extracting other gases from the atmosphere.
 
I just priced a 10 pt ( they called it 10 pts) and it was $589.00 way to much money. But they told me to make a metal container and put it in a plastic cooler and they will fill it for me. So I'm going to make a 3" round 12" high container and put it in a round cooler and insulate around it. I only need for it to hold 6 knives at a time, and get it filled when I need it. Thats my plan, what do you think??
 
ArtinNC said:
I just priced a 10 pt ( they called it 10 pts) and it was $589.00 way to much money. But they told me to make a metal container and put it in a plastic cooler and they will fill it for me. So I'm going to make a 3" round 12" high container and put it in a round cooler and insulate around it. I only need for it to hold 6 knives at a time, and get it filled when I need it. Thats my plan, what do you think??
Click to expand...



WAYYYYYY TOOO MUCHHHHH...
gads...shop around...

don't just LN2 in any old container. It's too cold and too expensive.

until you can afford a dewar, use Dry Ice and kerosene. Acetone is too flamable and kerosene will do the same thing with larger safety margin.
 
Just wanted to say... Great info here guys and thanks for posting it. It's saving me from having to ask about this in a few weeks.

-Josh
 
Jawilliams,
You will usually get about 1 point more hardness from the cryo in a nutshell.

Tracy,
Mine seems to last forever. I think I just got a really good one. I got it on fleabay for about $300 and it was brand new.

Guys keep your eyes open, the good deals are out there.
-John
 
aww shucks just put it in a mason jar and stick it in the fridge lol
You really need a dewar and a well ventilated area to store it.
 
The alternative to acetone or kerosene when using dry ice is 91% rubbing alcohol at the corner pharmacy.

A dewar is on my radar.

BC
 
You will get about a point in hardness but most important you will transform retained austinite into marstinite and that is the real benefit to cryo,
Stan
 
Some steels like the cryo better than others, D2 for example seems to hold an edge better with it in my opinion. That is just from me making Pocket knives with it and trying it out. CPM154cm I can't really tell the difference with or with out.
 
jawilliams0425 said:
OK, is this 1 point important, as in does it need it to make the knife that much better?huh1
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There are reams of text on the internet about this subject. Some for and some against cryo.

Bottom line: cryo is used a lot in the custom knife industry.

After tons of reading and speaking with other makers, I will cryo my knives....especially because I'm currently using SS.


BC
 
jawilliams0425 said:
OK, is this 1 point important, as in does it need it to make the knife that much better?huh1
Click to expand...

I think it is important in helping you make the best knife you can make. I've used dry before and it is better than nothing, but Liquid Nitrogen is a totally different story. We are talking near absolute zero. Where the dry ice mixtures may get -60F. A little more if you're lucky. To me, there were other tools I needed, but I work in stainless steel and I felt that if I was going to do my own heat treating, then I had to cryo as well. So I put some other things on the back burner to get the dewar. That's just my opinion.;)
-John
 
I always thought that Dry ice sublimated at around -100*F I never used a thermometer on it though -60 sounds right. I Didn't mix mine with anything when I used dry ice, just had a block and put the blades on it and by morning they would be all the way trough. Get the dewar if you can it lasts longer and you get more out of the lower temps.
 
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Rusty,
-100F is kind of a theorectical number, but it tends to stay around -60 to -70. Like I said it is better than doing nothing.
-John
 
I can't answer that because I've never heat treated any carbon steel. Indian George should know. Where you at IG?
-John
 
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