Dry Ice for Cryo?

[cmd]

Is dry ice useable in the cryo cycle of heat treating?

 

[Steve Hayden]

This is sure to draw a lot of varying comments, but if you look at all the steel company specs, dry ice temperatures are what they call for in cryo treating high alloy steels.

There is a lot of hype out there that has been promoted largely by the companies that specialize in N2 cryo.

The proven facts are that deep cold treatment converts retained Austenite to Martensite. I would be interested in seeing figures on the difference between retained Austenite percentages after CO2 quench and after N2 quench.

Tempering also converts retained Austenite, so if a temper is done first the cold treatment will have less total effect. Most manufacturers of tool steels suggest cryo before tempering.

 

[cooks 7]

if you do some searching you can find guys who have used dry ice and acetone to do cryo

 

[mete]

The dry ice /acetone mix gives you -100 F and the Liquid Nitrogen will give you -300 F .Choice may be more a matter of convenience and cost rather than performance .Either works fine. Do a search.

 

[cmd]

The dry ice /acetone mix gives you -100 F and the Liquid Nitrogen will give you -300 F .Choice may be more a matter of convenience and cost rather than performance .Either works fine. Do a search.

Thank you mete, good info. Searching cryo AND acetone turned up plenty - particularly some of your posts.

Harris Teeter around here sells dry ice that you can just ask for when going through the checkout line while picking up the groceries. There are a couple of them within 5 miles so it's very convenient if it will work well - they can store it for me until it's needed.

Chris

 

[Rob!]

Both work fine. Hold time for dry ice is about 48 hours. Hold time for Liquid Nitrogen closer to 2 months - and the liquid nitrogen fill costs me less. Results are the same for me, so I use liquid nitrogen.

Rob!

 

[Stacy E. Apelt - Bladesmith]

One advantage for dry ice is that it requires no special container.A Styrofoam cooler is fine for transport and storage.Single blades can even be cryo treated between two slabs of dry ice.The acetone slurry works better if you are doing several knives.
Use all safety procedures with the acetone mix.It is not only dangerously cold,it is still dangerously flammable.
Stacy