dry ice treatment

It doesn't mater if you use acetone or alcohol or even kerosene. You just want to create a cold slush. The liquid is just a method of getting better heat transfer. (there is actually no such thing as cold, just a lack of heat) Do not use rubbing alcohol as it has enough water in it to freeze with dry ice. I have been using kerosene and am going back to acetone as the kerosene foams so badly no matter what I do. I am a D2 guy and I have not used the snap temper and have never had a problem myself. I would like to go to LN but, the nearest supply to me is over 100 miles away. I would really like to know how long a 40 liter Dewar would keep the LN.
 
Jim,

Just a thought:

If there's a hospital in town, oxygen is being delivered.

The people who make oxygen end up with liquid nitrogen as a byproduct.

Maybe you could either get some from the hospital or get the supplier to deliver when they deliver to the hospital?
 
I have been looking at dewars and the time they will hold the LN seems to be dependent on two things (other than the dewar being of good quality, obviously), the size of the dewar and the size of the neck. The biggest problem with them is that they cost so much!!!!
 
bladsmth said:
That chart seems to show a HUGE difference between Cryo and Sub-zero treatment. I haven't hear of it being that much before. I would be interested in seeing the article it is part of, as these statements can be misleading without the context it is made in.
Click to expand...

leifjl said:
http://www.metalscience.com/techinfo_ASM.php
Click to expand...

This chart is from the above website. It shows a 316% increase in D2's wear resistance at -110 F & a 817% increase at -310 F. Seems awfully high . . .

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Shawn Hatcher said:
This chart is from the above website. It shows a 316% increase in D2's wear resistance at -110 F & a 817% increase at -310 F. Seems awfully high . . .
Click to expand...

This was from the same site? This chart has completely different data than the one I was referring to.
Well they're both internet "facts".
Without context at best, at worst from unknown sources.

I went with the graph I was referencing because it was claimed to be from asm handbook vol. 4 heat treating.
Seemed like the most reliable source I could find.
 
Shawn Hatcher said:
Scroll to the bottom of the page:
Click to expand...

ok, I found it at the bottom of their home page.
Well it is a cryo treating companies site so they probably picked studies to cite that make what they do seem extraordinary.

And JBS, yeah, I was thinking the same thing.
 
Oxegen plants end up with nitrogen alright, but, the neareest liquid air plant is over 100 miles away. The hospital gets its O2 in a large liquid container from them too.
 
When I lived in central WI just over a year ago, my local welding-supply/fire-extinguisher shop also carried both dry ice (blocks or chips) and LN (rent their container or bring your own to fill). This was in a town of 35,000 people on a peak tourism day. If you live near a city that has anything resembling an industrial sector, I'd be surprised if you couldn't find both. It's worth a look through the yellow pages, and a phone call or two.

This stuff is not a big secret, and knifemakers are certainly not the only ones who want it. Reach out locally, you might be surprised what you find :)
 
This is Crucible's data sheet. I do my first temper at 400 and my second temper after cryo at 500. I get a consistent tested 60rc on my A2 blades.
AIRKOOL®
(AISI A2)


AIRKOOL is an air hardening tool steel with high wear resistance and good toughness. Its combination of properties makes it well suited to a wide variety of tooling applications, particularly molding and processing of abrasive plastics.

Typical Chemistry
Carbon 1.00%
Manganese 0.85%
Silicon 0.35%
Chromium 5.25%
Molybdenum 1.10%
Vanadium 0.25%
Typical Applications
Blanking Dies Thread Roll Dies
Forming Tools Trim Dies
Punches Shear Blades
Gauges Wear Inserts


--------------------------------------------------------------------------------

Hardening

Preheat: 1100/1250F (595/675C), equalize, 1350/1450F (775/790C), equalize.

High Heat: 1750/1800F (995/895C), 30/45 minutes at temperature.

Quench: Air, positive pressure vacuum to 150F (65C).

Temper: 400/1000F (205/540C), hold 2 hours at temperature, air cool. Temper twice.

Cryogenic Treating: Refrigeration treatments may improve long term dimensional stability by transforming retained austenite. Refrigeration treatments should generally be performed after the first temper, and must be followed by a temper.

Hardness and Impact Toughness Data
Air cooled from 1775F(970C)

--------------------------------------------------------------------------------

Tempering
Temp. Hardness Toughness,
Charpy C-notch
°F °C HRC ft-lbs Joules

--------------------------------------------------------------------------------

As quenched 64 - –
300 150 62 - –
400 205 61 31 42
500 260 60 41 56
600 315 59 37 50
700 379 58 33 45
800 425 58 31 42
900 480 58 29 39
1000 540 57 41 56
1100 595 51 - –

--------------------------------------------------------------------------------



Size Change During Hardening


--------------------------------------------------------------------------------

Hardening

Temp.
Tempering

Temp.
HRC
Longitudinal

Size Change
%

°F
°C
°F
°C


--------------------------------------------------------------------------------

1775 970 400 205 62.5 +.07
1775 970 500 260 59 +.10
1775 970 600 315 58 +.09

--------------------------------------------------------------------------------


Surface Treatments
Airkool can be given standard surface treatments such as nitriding, titanium nitride coating, or hard chrome plating if desired. When gas nitriding, harden from the high side of the temperature range and single temper at 1000F (540C); then use standard nitriding procedures.

Annealing
A. Heat to 1600F (870C), hold 2 hours, slow cool 50F (30C)/hour maximum) to 1200F (650C), air cool.
OR
B. Heat to 1600F (870C), hold 2 hours, cool to 1400F (760C), hold 6 hours, air cool.
Typical annealed hardness: 197/241 BHN.

Stress Relieving
Annealed Material: Heat to 1200/1250F(650/675C), hold two hours, cool in still air.
Hardened Material: Heat to 25F(15C) below original tempering temperature, hold two hours, cool in still air.

Welding
Use air hardening tool steel filler material.

Annealed Material: Preheat to 400/600F(205/315C). Maintain above 400F(205C) during welding. Reanneal or temper 1400F(760C) 6 hours.

Hardened Material: Preheat to 25F(15C) below original tempering temperature (300F(150C) minimum). Maintain above 300F(150C) during welding. Cool to 150F(65C) after welding. Temper 25F(15C) below original tempering temperature.

Physical Properties
Modulus of Elasticity ..............................30 psi x 106 ..................(207 GPa)
Density ......................................................0.284 lb/in3 ...............(7861 kg/M3)
Thermal Conductivity ..........................15 BTU/hr./ft./F ............(26 W/m/ °K)
Thermal Expansion
Temperature Range
Coefficient of Thermal Expansion
°F °C x10-6 in./in./°F x10-6 mm/mm/°C
100-500 38-260 5.9 10.6
100-800 38-427 7.2 13.0
100-1000 38-540 7.7 13.9

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I live in a town of 6 thousand, 6,111 when the tourist are in town. We are the largest city for over 100 miles. The next county over has less than 300 people. The stockyards are our industrial sector. LOL. Actually there is a fairly large steel fab shop a few miles from town, but they only bring in liquid 02. I know all about welding shops and suppliers. I have ran a couple welding shops. I have also done repairs on air plants. Thanks for the input but, NO LIQUID N2 here unless you get it from Greatfalls or Billings, 110 and 125 miles away. You can get Dewars in the 30 liter range for about $500 up on Ebay. I might find one around here a rancher used for holding semen for insemination. If I kept it in a freezer it would gas off slower, you would just have to be careful not to asphyxiate yourself sticking your head in the freezer.
 
I paid like $250 for my 10 liter Dewar, roughly $25 to fill it, neck dia. 2 1/2".
If I don't open it often 2 1/2 - 3 weeks before I need to fill it.
Ken.
 
Ken, where did you find a 10 liter with the big neck? Also, how long of a blade can you get in your dewar? Neck size appears to be the sticking point with a lot of the samller dewars and some of the bigger ones too. You can't fit a bt kitchen knive into a 4 liter dewar with a 2 inch neck. ;)
kc custom said:
I paid like $250 for my 10 liter Dewar, roughly $25 to fill it, neck dia. 2 1/2".
If I don't open it often 2 1/2 - 3 weeks before I need to fill it.
Ken.
Click to expand...
 
If you are going to do a cryogenic treatment to precipitate carbides, thereby increasing the wear resistance, you will need to hold at temperature for @ 24 hours. If you are going to treat multiple blades at one time it could be beneficial to build a small freezer to hold the LN and blades in.
 
International Cryogenics LN2 Liquid Nitrogen Storage Dewar, 10 L with 2.25" inside diameter - for around $500. It would fits a few kitchen knives at the same time.
 
kc custom said:
I paid like $250 for my 10 liter Dewar, roughly $25 to fill it, neck dia. 2 1/2".
If I don't open it often 2 1/2 - 3 weeks before I need to fill it.
Ken.
Click to expand...

I'd also like to know where you got it.
Or could you tell me the brand?
Thanks
 
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