cryo questions

[Mike Davis]

is cryo a form of heat treat or temper? ive seen alot of posts mention it but am unsure of its purpose. is there specific steels that it is used on?

 

[Stacy E. Apelt - Bladesmith]

It is a bit of both.Quenching captures the structure of the steel in a desired form (martensite).Tempering is where the martensite is made stable and given desired properties.Both are part of the heat treatment. Cryo brings the steel down to a temperature where the retained austentite converts to martensite.The second temper tempers the new martensite.A second cryo catches any remaining Austentite, and the last temper tempers it all evenly.You can gain about 2-3 Rc points and a good deal of toughness with cryo treatment on steels like ATS-34 and S30V.

 

[mete]

The more complex steels from 52100 to S30V may benefit from cryo.At this point we know that it will reduce the amount of retained austenite ,other claims have not been proven. It should still be called part of 'heat treatment'.

 

[Dan Gray]

It is a bit of both.Quenching captures the structure of the steel in a desired form (martensite).Tempering is where the martensite is made stable and given desired properties.Both are part of the heat treatment. Cryo brings the steel down to a temperature where the retained austentite converts to martensite.The second temper tempers the new martensite.A second cryo catches any remaining Austentite, and the last temper tempers it all evenly.You can gain about 2-3 Rc points and a good deal of toughness with cryo treatment on steels like ATS-34 and S30V.

Stacy
second cryo ?
it makes some sense but.
I know of no one cryo'ing a blade twice? or the worth of the added cost of cryo'ing more that once, helium would be the answer if cost wasn't a factor.

yes, for those that don't know it does have to be done at least the once for the design of the steel.
twice yes on the tempering before and after. but if I were to cryo twice I'd add another temper. the first snap temper JMO

 

[mete]

Dan, I've heard of a second cryo but never have done it. In the old days when the 'subzero' quench was used it might have some application but the temperatures weren't that low. With -300F I think you would transform all the retained austenite that can be transformed .

 

[John Andrews]

Dan, I've heard of a second cryo but never have done it. In the old days when the 'subzero' quench was used it might have some application but the temperatures weren't that low. With -300F I think you would transform all the retained austenite that can be transformed .

I agree. It's always been my understanding with one treatment.

 

[Dan Gray]

Thanks Robert
I thought I was missing something somewhere new or old..
we when through the L/helium idea for even colder, if you remember right a long time ago
and I think this was in the discussion too..