Cryo baby cryo

[dbalfa]

Got me a dewar- finally
I wont tell you how much for fear of being called a thief...but it pays to have vet contacts

Now, I was wondering, is it of any benefit to cryo a SS blade after 1 temper cycle?

And, I saw Mete say that it is really part of the quench. I take from that that you should not worry about a snap temper to stabilize before cryo?
Do these rules apply to ALL SS or differ with types?

Thanks-

[Gabe Newell]

Cryogenic quenching effects vary quite a bit steel to steel and with the rest of the heat treatment.

A useful overview of an array of approaches tested on A2 is at:

http://www.airproducts.com/NR/rdonly...3005019GLB.pdf

For M4, you get the best benefit with high austenitizing temperatures, no snap temper, and low tempering temperatures (but only one temper is needed as the cryogenic quenching has given the benefits that multiple temper cycles are usually needed to attain).

[nate d.]

the reaction to drive the austenite to martensite is benefitted in my opinion by doing the cryo treatment after quenching to room temperature. why do you want to impede the reaction by placing tempered martensite in the matrix? this is the reason i try to drive as much austenite to martensite as i can by doing the cold quench first followed by tempering the martensite to tempered martensite. also by the way on the soak issue, in LIN that reaction is instantaneous, so don't think there is much of a difference between 5 minute soak and overnight, the reactionn in LIN happens in seconds. Now that said i still let it sit in the LIN 5 or 10 minutes. don't do using the previous argument for dry ice, i'm not confident there as much of a driving force with its use vs. LIN.

[Gabe Newell]

The theory behind doing a temper before cryogenic quenching is to reduce risk of cracking. For example, Crucible recommends that on some datasheets on some steels for parts with geometry where cracking is a concern.

However it also significantly reduces the benefit of cryogenic quenching (at least in M4 austenitized at 2200 F) in reducing retained austenite.

On M4, quenching in liquid nitrogen for 24 hours offers no significant benefits over quenching for 1 hour.

On M4, quenching in liquid helium offers no significant benefits over quenching in liquid nitrogen.