How Cryo Changes Steel

[Larrin]

I wrote a series of articles about how cryo changes steel, including transformation of retained austenite, increase in hardness, reduction in toughness, and improvement in wear resistance. There is a lot of debate surrounding cryogenic processing studies so it was a lot to go through. I also included toughness studies we performed on Z-Wear (CPM CruWear) and the CATRA studies on 154CM that looked at cryo. Everything you wanted to know and more about cryo.

https://knifesteelnerds.com/2018/12/03/cryogenic-part1/

https://knifesteelnerds.com/2018/12/10/cryogenic-processing-of-steel-part-2/

https://knifesteelnerds.com/2018/12/17/cryogenic-processing-of-steel-part-3/

 

[hugofeynman]

Very interesting results. Please correct me if I’m wrong, Larrin, so basically there’s no need to go the deep cryogenic treatment route, the deep cooling (-85C) is enough for all purposes? And there’s no need to let the blade in the deep cooling environment during 36 hours, 20-30 minutes will be enough (RA converting is temperature related, not time related)?

 

[Larrin]

Very interesting results. Please correct me if I’m wrong, Larrin, so basically there’s no need to go the deep cryogenic treatment route, the deep cooling (-85C) is enough for all purposes? And there’s no need to let the blade in the deep cooling environment during 36 hours, 20-30 minutes will be enough (RA converting is temperature related, not time related)?

Subzero is sufficient for transforming most of the retained austenite in most cases when "continuous cooling" is used. When there is a snap temper or a delay before cold treatment than liquid nitrogen is more effective. For transforming retained austenite the time isn't a factor. There are some claims related to carbide formation and wear resistance with longer times that I don't trust which is covered in Part 3.

 

[hugofeynman]

Neither trusts Fredrik Haakonsen.

His take on the matter:

Fredrik Haakonsen about deep cooling vs cryo:


https://edgematters.uk/thread/9605-heat-treatment-discussion/?postID=124167&highlight=Cryogenic+treatment#post124167


“It is correct that most high alloyed steel often need deep cooling to remove retained austenite, so deep cooling is often recommended. Deep cooling is cooling down to -85 C. There is no evidence that cooling below -85 C, like cryogenic treatment, gives any additional effect on this.” Fredrik Haakonsen.

Even Roman Landes in his low temper cpm3v heat treatment doesn’t mention cryogenic treatment, just deep cooling.

 

[Larrin]

Yes most of the data sheets also refer to dry ice temperatures.