Cryo question

S

smorgan345

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Mar 8, 2007
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I read that cryo treatment is important for stainless. I'm using 440C so I thought I should? I don't want to skip anything important with all the work I've put into these knives. I know where to buy dry ice but I'm not sure of the logistics on mixing it with Kerosene and soaking them. Can I put dry ice with Kerosene in a cooler or will it freeze and crack it? Should it be a steel container.... -100F is pretty damn cold! Do you just pour in the Kerosene and then float the ice in it? Any advice would be appreciated. Thanks.
Scott

unrelated question, in between tempering cycles, how cool should you let the blade get and for how long. I was just planning on letting come down to room temp and then running it back up in one cycle on the kiln, is that bad?
 
Put your blade in a metal can completley fill around it with dry ice chips and slowly start adding the kerosene or denatured alcohol. Its going to boil like hell for awhile so do this slowly or it will overflow. When the liquid is above the blade just leave it overnite . Take it out let it come up to room temp and then start your draw.
Ken.
 
I use a metal container in a cooler to hold the dry ice and acetone.

The cryo should be done after the quench and before the first full temper ( it is the bottom end of the quench ,actually). A short snap temper at 200-300F is advised after the steel has cooled to room temp. Then do the cryo.

Pre-Heat to 1400F > Heat to 1900-1950F > plate quench > cool to room temp > snap temper at 200-300F > cryo > warm to room temp > first temper at 350-385F > cool to room temp > second temper
 
Rubbing alcohol works also. I usually let them sit for 10 hrs in a stainless container (drywall mud pan) inside a cheap styrofoam cooler inside a chest cooler. With 2 lbs. of dry ice and 3-5 blades the dry ice lasts 12-14 hrs or longer.
 
I use a foam cooler inside another foam cooler. I use the medical transport kind that are 2-3" thick. Frozen steaks also use the same coolers. I stick 5 lbs. of dry ice in it, no kerosene or alcohol, and close both containers. Everything inside the interior cooler will be the same temp. Do not tape the coolers shut, they will pop open. 5 lbs. lasts about 2 1/2 days this way. The metal container is only necessary if you use kerosene to keep from dissolving the foam.
 
Correct me if I am in error, I have been taught to place the liquid in first and add the dry ice to the liquid rather than adding the liquid to the dry ice?
 
Yes, it is best to add the solid CO2 to the acetone/alcohol bath slowly. It will boil a lot at first, and then become a slush.
 
I understand that using the liquid will transfer heat out of the blades faster than just the dry ice like zaph does, but over a 12hr cycle does the rate matter that much? I found that just putting certain blades into the nuggets caused them to moan and groan within seconds, so they are cooling fast! Is there another reason than speed to use the liquid? My blades get buried under dry ice nuggets, wrapped in cloth to reduce the rate at which the heat is drawn out (I figure there is less thermal shock that way)
 
Thought, I would add to this post. When the steel gets cold it will make a noise like the vocal sounds of whales, really!:eek::)
 
When I lay a blade on a slab of Co2 ice it vibrates a little and indeed moans a bit.
 
The cryo part of the quench is alot like tempering,it is a matter of time and temp.The RA continues to transform for some time.Most of the sheets I have read suggest at least 6 hours,but I usually leave mine overnight.
Stan
 
Solid CO2 sublimates and gives off the gaseous CO2. The problem with using just the dry ice is that gaseous CO2 is a poor conductor of heat. That is the reason you can handle it ( like a hot potato). The liquid acetone/alcohol provides a complete contact with the blade, and will lower it to the temperature of the slush. This can take it down to -70F. A blade just placed on dry ice, or even packed in dry ice chips only reaches -50F. A $11 gallon can of denatured alcohol, or a $15 gallon of acetone, is the simplest way to deal with this.

When placed on a slab of dry ice, the reason the blade makes noise and vibrates is it is bouncing around on a layer of gas.

Zaph and others:
The insulation quality of the cooler you use is of little matter. The dry ice will sublimate unless it is held at a very low temp and/or under pressure. The fact of its low heat transfer is why it doesn't just evaporate all at once in a second.

To prove this, take a chip of dry ice the size of an ice cube. Set it on the cutting board in the kitchen,at room temp,and at the same time place an ice cube in the over which has been pre-heated to 200. The difference in temp is roughly the same. I bet the ice cube is gone a lot faster than the dry ice sitting on the counter is.

Charlie, I didn't know you did any stainless HT or cryo?
 
Dry ice gets about -100 F and LN gets -300 F. The real cryo effects are found only at -300 F. -100 F will only reduce retained austenite.
 
C'mon guys. How many times do I have to come on here and tell you NOT to use Acetone???

Use Kerosene! It is both cheaper and safer than Acetone.
 
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