AEB-L Heat treat question

Wally76

Member
I recently came into possession of some AEB-L steel and I have some questions regarding the heat treat of this steel. My first question is about the initial ramp to 1560°F and equalize step. Can I start the heat treat with the knives in the oven or do I put the knives in once the oven reaches 1560° F? How long will I need to hold at that temp to equalize? I have read that this metal can be cryo treated with dry ice and does not need a soak but to bring the metal to -95°F and then temper twice at 2 hrs each. How long should the knife soak in the dry ice mixture (91% ISO Alcohol and dry ice)? And lastly, do I need to cryo treat between each temper cycle? I have read this in only one of the articles but thought it would be worth asking.

Thank you for your time!
 
I think you will like the AEB-L. I always put the blades in right away, ramp to the equalize and then let them soak for 10 minutes or so, just to make sure the blades are at the equalize temp. I only used the dry ice/alcohol soak once before I got an LN set-up. I used denatured alcohol and not rubbing alcohol. I just kept putting the dry ice in the alcohol until it became a slurry. I let the blades soak for an hour or so. You only have to do one sub-zero, then your two temper cycles. Please make sure you let the alcohol completely gas off before putting it back in a container. Last week a fellow knifemaker did a sub zero slurry using dry ice and acetone. As soon as he was done, he put the acetone back in the metal container. A short time later the can had swollen up. He literally had to call the fire department, who called the local bomb squad to remove the pressure from the can. A VERY dangerous situation.
 
I very much appreciate the information! Pretty excited to try out the cryo aspect of the process. Future plans will include LN treatments but will need to save for the Dewar . And for the acetone... It's a no go for this guy! My wife likes the house AND location of it in the neighborhood . Thanks again!
 
I would temper 1 cycle then do the cryo. Seems to me there's to much stress in the steel after hardening. Just my 2 cents. Harden, temper, cryo, temper

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The reason you don't want to temper prior to the sub zero or cryo is exactly why you're doing the sub zero/cryo in the first place. To eliminate the retained austenite, and tempering stabilizes retained austenite. (Cryo with LN2 has other benefits besides RA reduction....topic for another thread).
 
I always heat-treat, cryo, then double temper. I was told cryo only needs to be to temp . You did not need a soak at -320 degrees. Think this came from Larrin Devin Thomas son.
 
Stuart is correct, it is VERY important to go directly from the quench to the freeze/cryo. I've been doing it this way for years and have never lost a blade. If you do a temper first you will stabilize the RA and once it has been stabilized nothing will convert it to Martensite, short of completely starting over.

Whether or not a freeze/cryo soak is needed depends on the alloy. AEB-L only needs to get down to the MF which is -70 F if I remember correctly. Other alloys need a soak in order to set up the steel for the formation of ETA carbides during tempering.
 
"Other alloys need a soak in order to set up the steel for the formation of ETA carbides during tempering". Exactly. Darrin knows this already, but for the sake of clarification.....just remember that the eta carbide precipitation does NOT occur with sub zero temps of dry ice (-100F). Only full cryo temps with LN2 (or colder) and extended soak times.
 
Stuart is correct again. Its hard enough to understand this stuff but explaining it is completely different. Omitting one tiny detail can lead someone down the wrong path. Maybe that's why these threads always give me a headache. LOL
I wish Kevin would finish that book he's been promising us. That way, when someone has a question we could just tell them to go to page XYZ for the answer. LOL
 
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