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/

 

[HRC_64]

Wow, thats a lot of work. People should definitely read these articles. Cheers

 

[Barmoley]

Very good stuff. Thanks for the work Larrin.

 

[CoteRotie]

It's been many years since my materials science courses in school, but it was one of my favorite subjects. Great stuff, thanks, Larrin for sharing all the work with us.

One thing I'm surprised about:

"We also looked at the effect of cryo where we compared no cryo, and 1 hour, 12 hour, and 36 hours in liquid nitrogen."

After the steel reaches thermal equilibrium with liquid nitrogen, what's going on at -195°C on a molecular level that results in changes in the material properties?

In my ignorance I would think that there would be very little change between 12 hours and 36 hours at that temperature.

 

[Larrin]

One thing I'm surprised about:

"We also looked at the effect of cryo where we compared no cryo, and 1 hour, 12 hour, and 36 hours in liquid nitrogen."

After the steel reaches thermal equilibrium with liquid nitrogen, what's going on at -195°C on a molecular level that results in changes in the material properties?

In my ignorance I would think that there would be very little change between 12 hours and 36 hours at that temperature.

I agree, hence my skepticism. That study was precipitated by those cited in my articles where they claim there is a difference.

 

[Interapid101]

Must be a pain in the butt to keep the material submerged in LN2 for that long. Lots of evaporation can happen, even in 24 h in insulated dewars. I guess that's what grad students are for: going to the lab at 2AM to pour LN2 from one container into another.

Anyway, another great bunch of articles. I applaud you for resisting the urge to make broad conclusions for steel as a whole based on your work on Z-wear. Really like how you are careful to only make claims that are supported by multiple data points.

 

[CoteRotie]

I agree, hence my skepticism. That study was precipitated by those cited in my articles where they claim there is a difference.

Got it, just surprised that there seems to be a lot of effort by others going into long cryo treatments.

 

[RDalman]

Interesting, thanks!