Ive been around for a while now in lurking or active form and havent seen a serious thread on this subject. What does cryo do, how cold is cold enough, is it cheap to do, etc. As usual, I have my own ideas about what it does and how, but I would like to hear from the people who have used knives treated this way, or those who do the treating. Technical info is also welcome. Cliff, I'll get the chart we talked about on as soon as I find it.
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- Thread starter 99tc675
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Stacy E. Apelt - Bladesmith
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Welcome 99tc675. Fill out your profile so we know where you live and a bit about you.
There have been many threads on cryo. Dr. Larrin Thomas has written a book on knife HT and covers it well. The book is Knife Engineering, and it is almost a must have for knifemakers. He has a site called Knife Steel Nerds where you can read many in depth articles. https://knifesteelnerds.com/
Short simplified answers:
Cryo is used on complex high alloy steels ... usually stainless steels.
Cryo is a very cold treatment to the bottom of the quench curve that completes the transformation of the austenite into martensite and then converts some carbides.
Cryo will gain 1 to 3 hardness points over a sub-zero treatment.
Cryo is usually done in liquid nitrogen at -321°F.
Sub-Zero treatment is done in a dry ice and alcohol slurry at -100°F. It is not cryo, but gets these steels to the Mf point.
There have been many threads on cryo. Dr. Larrin Thomas has written a book on knife HT and covers it well. The book is Knife Engineering, and it is almost a must have for knifemakers. He has a site called Knife Steel Nerds where you can read many in depth articles. https://knifesteelnerds.com/
Short simplified answers:
Cryo is used on complex high alloy steels ... usually stainless steels.
Cryo is a very cold treatment to the bottom of the quench curve that completes the transformation of the austenite into martensite and then converts some carbides.
Cryo will gain 1 to 3 hardness points over a sub-zero treatment.
Cryo is usually done in liquid nitrogen at -321°F.
Sub-Zero treatment is done in a dry ice and alcohol slurry at -100°F. It is not cryo, but gets these steels to the Mf point.