Quench Speed and Retained Austenite?

[shqxk]

Faster quench likely to yields higher HRC on the same steel, not sure if this relates to the lesser amount of RA?

 

[TheEdge01]

https://knifesteelnerds.com/2021/07/19/which-quenching-oil-is-best-for-knives/

This site has some awesome info on quench speeds or anything HT related.

 

[shqxk]

https://knifesteelnerds.com/2021/07/19/which-quenching-oil-is-best-for-knives/

This site has some awesome info on quench speeds or anything HT related.

Well, I'm not asking which oil is the most suitable as a quenchant...

My question is how quench speed effect retained austenite.

Even air hardening steel benefit from faster quench that can result in higher hardness. I want to know what is the mechanism behind this and if it relates to the amount of RA.

 

[Stacy E. Apelt - Bladesmith]

My take is that any quench resulting in higher hardness will result in lower RA. Hardness is relater to the formation of martensite, which would reduce the amount of austenite.

 

[NYMet]

Quench speed will have two effects. It can help avoid many unwanted structures (following continuous cooling curves) and it also forces a faster martensite transition which maximizes hardness. So there is a minimum quench rate needed to avoid structures you don't want and a maximum rate to get ideal martensite transformation. Theoretically you want to quench as fast as possible without cracking the material. Each grade will have a limit where the stress from quenching will be too much for it to handle. Happens when you quench air hardening in oil or water. Get away with it and the structure is beautiful. Don't and you get shrapnel.

 

[Keith Nix]

No one wants to talk about cryo for reduction or elimination of RA?
Or that austenitizing temp has a great effect on total RA?

 

[DeadboxHero]

Faster quench likely to yields higher HRC on the same steel, not sure if this relates to the lesser amount of RA?

Seems more like opening a can of worms, RA should be controlled more by avoiding plate martensite and avoiding over austenitizing more than quenching speed.

There is an effect to hardness with faster quench speed but there will always be some hidden RA that stabilizes, and is finer than can be seen or detected with optical microscopy or HRC and Microhardness testing.

 

[DeadboxHero]

https://knifesteelnerds.com/2021/07/19/which-quenching-oil-is-best-for-knives/

This site has some awesome info on quench speeds or anything HT related.

Cryogenic Processing of Steel Part 1 - Maximizing Hardness - Knife Steel Nerds

What happens during cryogenic processing of steel? How does it lead to increased hardness? How does retained austenite play into this?

knifesteelnerds.com

This is where the subject is discussed.

Mechanism for stabilization is also discussed in Knife Engineering chapter 23, pg 290-292
.