Air cool. I would be worried that it could warp or even crack dunking it in water.

What I am about to say may shock people than blades, <img src=' http://www.americanbladesmith.com/ipboard/public/style_emoticons//biggrin.gi f' class='bbc_emoticon' alt=':D' /> but I actually quench just about every blade in water between temper cycles. I do it mostly to get to handling and Rc testing the blade as soon as possible- time is money, but there are actually metallurgically sound reasons to do it as well. The difference it can make in the final product is probably a matter of squeezing that last insignificant 1 to 2 percent but it can't hurt and it gets me back to work quickly. Some richer alloys may benefit more from a quick cool by avoiding certain precipitates that form on the slow cool down, but just about any steel can have some traces of retained austenite, mostly unnoticeable, like 6% or less. If there are any smidges of retained austenite, the tempering will destabilize it by taking its carbon for tempering carbides, the quick cool will help minimize some of the precipitates within the martensite packets and help kick the austenite over into martensite instead. If I can have more martensite instead of cementite/ferrite I will take it. I have yet to see any distortion from point first dipping the blades and have never had any cracks in the 350F-450F tempering range.

Jim, I put mine in the sink and cool them off with a water spray, then back in for the next cycle. A time saving trick learned from one of our MS. Never an issue.

Bob

Thanks guys - you might laugh - I read your two responses and walked into the kitchen, took a blade off the stovetop that had just come from the oven and cooled it in water

Again and again, thank you for sharing your knowledge.

I have been water quenching them in between temper cycles and after. I have stashed the last two, 80CrV2, in the deep freeze after the last temper cycle. Not sure that is helps the steel but my wife is happy they are not laying around the kitchen waiting until I can get back to them.

Chris

It is worth mentioning that if anybody notices a measurable gain in HRC from rapid temper cooling or a kitchen freezer with the simple alloys we are discussing, it would be worth wile to reexamine your hardening procedures. Simple carbon and simple alloy steels should not normally have enough retained austenite to effect HRC, and if it does climb to those levels it is most often a result of slight overheating or, occasionally, something funky in the quench. I don't notice any increase in HRC (Hardness Rockwell C-scale) from the temper-cooling I do, but I have found successive tempers to have a homogenizing effect on the HRC spread as the numbers come down from tempering.

I come out of my temper and quench in my five gallon water bucket.

Back in the oven.

Same after second temper and then into the shop to work on it.

Easy-peasy.

I too cool with water after the temper. There have been a few times when a slight warp occurred during the temper which I was able to correct by cooling one side under a stream of water after the temper. I've never understood why a blade should come out of the quench straight and warp during tempering but it can happen. <img src=' http://www.americanbladesmith.com/ipboard/public/style_emoticons//smile.gi f' class='bbc_emoticon' alt=':)' />

Gary