D2 Air quench temp?

whisperer

Member
Is there a preferred temperature for the air to be at with an air quench on D2? I guess what I’m asking is am I better to air quench over my forge for a few hours in the shop….. or hang it outside in the winter at -20 deg? And why?
 

Alden Cole

Well-Known Member
I wouldn't hang it above your forge, if your forge is still hot. Just cool air, or Aluminum plates. Some people use a fan.
 

KenH

Well-Known Member
I've never worked with D2, but other "air hardening" steels are usually best clamped between aluminum plates - helps keep blade straight if nothing else.
 

whisperer

Member
Thanks for the replies guys.

Still trying to understand this. So “air quenching” will cool quickly enough to lock the carbon and you won’t benefit from quenching cooler to be harder, or longer to be more soft? So, it just is what it is?
 

Kevin R. Cashen

Super Moderator
There are just enough substitutional Cr atoms in D2 to retard corrosion but not quite enough to make it fully "stainless." But there is enough distortion of the lattice to resist the martensitic transformation enough to make retained austenite problematic. Slowing the cooling at all beyond what is necessary for hardening will only increase the retained austenite to increasingly higher levels. E.g. - the slower the air quench, the less complete the hardening process, and the more the need for post quench cold treatments to achieve full hardness.
 

whisperer

Member
Thanks Kevin. Very helpful information.

so what I’m hearing is I can still do a differential quench with D2. In other words, the ground thinner sections (roughed out edge shape) will quench harder because of quicker heat dissipation than the thicker sections. I just have to experiment to get it right.
 

Kevin R. Cashen

Super Moderator
Umm, no, that really won't work in the way you may be thinking. Differential quenches/hardening are the result of the formation of pearlite at the spine and martensite at the edge. In this case, the softer phase (pearlite) is the most stable phase possible in an iron-carbon system. D-2 cannot make pearlite, this is what makes it air hardening. So, what you will get is still martensite, but it will be mixed with austenite- literally one of the most unstable phases you can have. Yes, you will gain some toughness, but it will be because you have not completed the hardening process and should you get conversion of the metastable austenite later on it can be an issue in several ways.
 

whisperer

Member
Okay, darn. Thanks for making it more clear.
Sometimes I get an idea in my head, and I like to experiment, but I’m not too much an “hold my beer and watch this” kind of guy. Thanks for the info!
 
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