cryo question

D

dodo s

Joined
Apr 2, 2016
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hey guys quick question when you do a cryo treatment i liquid nitrogen is there any pre cooling or anything like that or just dunk the blade in the liquid nitrogen, Alos i have heard people say to leave it in for 2 hours and some say over night????different steel different time? or just some people do it differently than others/ thanks guys!
 
These questions do better in the knifemakers shop talk section. General Knife Discussion is for discussing completed and mostly production knives, not how to make them.
 
Cryo is part of the HT process and implies -300 F [LN temperature ]. Let the quenched blade come to room temperature then dunk the blade , point or edge down, into the LN.Suspend it in the LN for 4 to 6 hours .This permits the formation of eta carbides on tempering . Tempering is done once the blade is up to room temperature !
 
For most people, the primary purpose of cryo/cold treatment is to reduce RA particularly in more highly alloyed steels. Eta carbides MAY be an added bonus. According to folks like Roman Landes, the RA transformation immediately after quenching is very quick once you get down to target temperature.
 
And there is no point of couple of hours LN immersing.

Mostly will be ok for max 10minutes.
 
The transformation of RA to martensite is a fast shear type reaction .
However the formation of eta carbides involves changes in the lattice giving room for the carbides to form upon tempering ! This takes time apparently different in each type of steel. This is more of a diffusion type reaction like the final tempering !
 
thanks guys! what about doing cycles i have hear the knife can benifit from being dunked in LN after the quench for a few mins then taken out let warm to room temp and doing it again and maybe a third time....any truth in this?
 
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