Who keeps LN2 on hand?

D

DavidHoback

If you see me posting, remind me to STFU & leave.
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Dec 10, 2014
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I am in the process of building my own heat treat oven, and going to pick up a 10L Dewar for LN2 Cryo. There is a welding supply house right near me that will fill a 10L Dewar for about $20(score!). I use CPM3V & CPM20CV almost exclusively for my knives, which require Cryo during heat treat. To this point I have always been very happy with Brad's heat treating @ Peters. But it's that time for me to start doing it myself. Not because I need to, but because I want to. I started making knives for the same reason I learned to build firearms so many years ago. Because I WANTED to! :D Being disabled, I have far too much down time. I'm in too much pain most of the time to do much. So that is my research time. But the couple hours or even just 1, I might get each day, I like to do something in my workshop room. I still build firearms, when I can. But too expensive to do one after another. Knifemaking is realatively cheap, as a continuing excursive. Once the equipment is purchased. Being able to build your own equipment REALLY makes it economical.

This is a wonderful time for knife makers. And I enjoy being part of it. Would like to hear from others using a Dewar for Cryo treatment. How long does the LN2 last. What do you do for blades too large to fit in your Dewar? How long do you Cryo each blade for?
 
I have a Wide Mouth 30L which has not been a problem with fitting Large knives up to 16" like a large Chef knife. I tend to work in batches so I will process 20-50 at a time over 2 weeks and hold time is close to 45 days less evaporation. Local Welding shop will fill it up for about $65 so they hook me up ok since I've been buying all my welding supplies from them for years. Depending on the Type of steel and it's particular HT protocol it could be a little as a quick dip and roll to a 24hr soak or longer.
 
Willie71 said:
I have a 20l, and it lasts 3-4 months between fills.
Click to expand...

How often do you HT? I find that with the number or blades going into and out of the Dewar every few hours or so creates more of an evaporation issue...Liquid that wants to become gas as soon as the plug is removed and as blades are removed or inserted only gives me +/-45 days and I try not to let it RUN DRY so it holds temp better when filling.
 
Busto said:
How often do you HT? I find that with the number or blades going into and out of the Dewar every few hours or so creates more of an evaporation issue...Liquid that wants to become gas as soon as the plug is removed and as blades are removed or inserted only gives me +/-45 days and I try not to let it RUN DRY so it holds temp better when filling.
Click to expand...

I do batches of knives that require cryo, probably 5-8 at a time, but only once a month or so. I'm part time, so it sits closed up most of the time.
 
Is it better to store the filled Dewar outside during cold months, and inside during hot months?
 
I have a 10L dewar that I keep in a heavily insulated box (8" of expanding foam insulation) it'll keep it for maybe two months. Around here it costs about $50 to get it filled. I usually wait until I've got 30-50 stainless blades ready to go before get it filled. That way I know I'll get my money's worth. Then I'll use it as needed until it goes empty. Next time I have a big pile ready I get it filled again.
It's worth trying a few different places for your nitrogen too. Two places local to me sell it. One is $5 a litre, the other is $9
 
Batch HT is the way to go for sure to get the most efficient use of the LN2. When I get a batch of steel I already know what patterns are going through the process of cutting grinding Ht'ing so I plan for 2 weeks of heat treat and cryo as needed even if I'm working ahead to have knives ready without handles not on order.
I just keep the Dewar in my Garage winter or summer it's climate controlled. If you intend to keep it outside I would think that Geoff's
idea of having an insulated box might be your answer. WoW $9.00 a Ltr is higher than Ribeye Steak!!!
 
I scored on price! Local welding shop about a mile from my house will fill a 10L Dewar for $20! That's sounds cheap to me! I like it! I like how everything is coming together.
 
Yeah price fluctuates usually $2.00-2.25 per liter where I'm at.
 
The Republic of canuckistan and low prices don't usually go together.... Doesn't help that I'm on an island either so a lot of local places tend to gouge the captive market.

Even after factoring in shipping, taxes, and exchange rate it's cheaper to order most things from down south. Even at your dollar being about $1.30 of ours, it's still cheaper for me to order Baldor buffers from trugrit and get them shipped up, than ordering one from within canada
 
I see your situation as dire being held hostage by local merchants...that sux!
 
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