Cryo - How soon after quench?

B

Brad M

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Jan 17, 2007
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Hello everyone. I'm new to the forum so please straighten me out if I inadvertantly break a forum rule.

I mostly use ats, 154cm, and just starting to use cpm s30v. I do my own heattreating (electric furnace, aluminum plate quench, etc) but I am not equipped for cryo. How effective will cryo be if I flash temper, then send out my blades for cryo? There would be a few days between and I've been told by a few trustworthy sources that cryo should be done immediately after quench or first temper.

I think I'll send a few out for cryo and compare hardness to non cryo'd (with same heattreat). I'll post results if anyone's interested.

Any thoughts around this? Thanks in advance.
 
Cryo is most effective if you get it in as soon as possible, 24 hours is way too long to wait.
 
As explained to me by Crucible, the cryo is part of the quench. If you are using D2 or A2 or something similar where you have to do a stress relief first, then you could probably wait. On those steels where it is part of the quench, I'm not so sure about waiting.

However, that said, cryo is used for optimum steel perfotmance. Since you can do the steels you mentioned without cryo and they still work, give Crucible a call. They are more than helpful

Explain what you want to do and ask them about it. My understanding is that martinsite still converts over time (years) in the air hardening steels, so you might be able to get by with it.

Let us know what Crucible has to say.

Gene
 
The ideal transformation is continuous, right through RT and down into cryo.
Minimizes the stabilization of retained Austenite.
 
Thanks guys. Looks like I better buy some equipment and learn how to handle liquid nitro. I'm still curious what Crucible will say so I'll call and let you know what they tell me.
 
I contacted Crucible today - WOW, they have incredible tech service. They replied almost immediately and I was able to talk to three individuals regarding the "cryo - how soon?" question.

As far as crucible is concerned, the cryo treatment doesn't have to be done immediately to be effective. They don't fully agree with the belief that over time some of the retained austenite may "stabilize" and said that it is a process driven by temperature rather than time.

It was also suggested that cryo isn't always neccesary with all blades - it depends on the intended use. Yes, hardness (edge holding) will be improved but we may sacrifice some "toughness".

I was later called back by another gentleman from Crucible and he suggested that if I want to cryo immediately to try the freezer as an experiment. I could actually throw the blades in my yard, it's a balmy -25 degrees here today.

Anyhow, I am going to test these theories on my next batch of blades.

2 blades - HT, first temper, final temper, hardness test

2 blades - HT, first temper, freezer a few days, final temper, hardness test

2 blades - HT, first temper, send out for cryo, final temper, hardness test

I'll try to maintain close controls (same temperatures / soak times, etc). If anyone is interested I'll post the results.
 
Brad, a hardness test doesn't show toughness, and IIRC, cryo treating doesn't have an appreciable effect on hardness. I've been known to be mistaken, though...
 
howiesatwork said:
Brad, a hardness test doesn't show toughness, and IIRC, cryo treating doesn't have an appreciable effect on hardness. I've been known to be mistaken, though...
Click to expand...
Cryo does increase hardness. A rockwell test is a very good way to see if you're converting retained austenite, at least when you have enough of it in the first place. You shouldn't see an increase in toughness from cryo anyway, so I'm not sure why we'd be worried about that.
 
I'm sure I was told there would be an actual "loss" in toughness - I assume negligible though.
 
I have an article about cold hardening on my site Scary sharp. It has the pros, cons, and times, all you would ever need to know about cryo or cold hardening.
 
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