- Joined
- Jun 11, 2006
- Messages
- 8,651
I don't personally use AEB-L for my knives but I do heat treat it for other people and thought I would share my frustration about this steel with others. It's not really a frustration but more like an acquired taste and once you know what to expect it's not to bad to deal with. I'm doing a large batch of AEBL right now and I documented each blade with many RC tests through the entire process to give you an idea the kind of roller coaster ride to expect.
First I run my oven at 1900°, my oven runs a tad hot and 1900 deg seams to be the sweet spot for AEBL in my oven. I have found that if you over heat the steel you will get a very low as quenched hardness; we are talking in the low 50s and possibly lower. I adjusted my heat till I got a good "as quenched" hardness of 59-61RC. I soak for 10min at this temp once my oven is back up to 1900° after opening the door and inserting the foil envelope. If your testing blades right out of the quench you need to be prepared for the shock of seeing quite low numbers. Don't freak out like I did the first time. AEBL seams to have very high retained austenite and the hotter you go the more it seams to keep.
I have noticed that if you don't zero in on the optimum austenite temp you will experience a much higher chances of warps and bows. You will still get an odd one that will come out of the plates like a banana but the chances are greatly reduced. I'm guessing the warping is tied to the amount of retained austenite. I quench between quench plates and do it as smoothly and quickly as possible. I set the bottom plate across the back of my anvil and then lay the foil packet down and set the other plate on top and use a Irwin quick clamp to apply pressure. The trick is to leave the blade between the clamps for a decent amount of time. If you pull it out to soon even if it's cold it will bow. AEBL is rather soft right after a quench for a good amount of time.
After quenching I go straight to the cryo. Research seams to show that if you wait and don't cryo right away the austenite will stabalize over time.
A cold treatment is a MUST, if you don't hit the temp dead nuts then your left with a rather soft blade. I use liquid nitrogen because I use it for other alloys that need the -300° so why not use it for the AEBL. But you need to use dry ice with denatured alcohol at least. It does not seam to need any soak time in the cold bath but I do around 5-10min. After this you will have a bump in hardness. The amount depends on your starting hardness. I have seen it go from 50ish to 60-62rc. But 62-63 seams to be the max I can get out of the cryo even with my tweaked 1900° soak. But some times it can take some time to hit this hardness after the cryo for some odd reason.
You might be saying to yourself but wait how am I going to get 62rc after temper if I'm already there before tempering. This is where things get weird and I don't know the reason why but it's a head scratcher. I do the first temper at 300° for 2hrs. After this I test the hardness again and poof it's at 64-65RC. After this bump the temp up till you get the hardness your after.
You might notice from my timing that everything moves in one fluid motion so I'm able to process batches efficiently. While the oven is heating up I foil wrap all the blades. Then once the oven is ready I put one blade in the oven and let it soak for 10 min. Then it comes out and goes between the quench plates. While it's cooling I put the next blade in the oven. Then about 10 min later I remove the blade from the quench plates and pull the next blade from the oven and it goes between the quench plates. I open the foil pouch and remove the blade and it goes into the cryo. 10min later the process starts over and the blade is removed from the cryo to make room for the next blade moving down the line. I just keep moving all the blades one step every 10 min and before long all the blades are done and ready to temper. This process allows me to give each blade the attention and identical heat treat as the blade before and after it.
I don't claim to be an expert or a metallurgist I just know what I have discovered through testing. If I have made an error in my assumptions I would like to know about it and would like to understand why this steel acts the way it does.
First I run my oven at 1900°, my oven runs a tad hot and 1900 deg seams to be the sweet spot for AEBL in my oven. I have found that if you over heat the steel you will get a very low as quenched hardness; we are talking in the low 50s and possibly lower. I adjusted my heat till I got a good "as quenched" hardness of 59-61RC. I soak for 10min at this temp once my oven is back up to 1900° after opening the door and inserting the foil envelope. If your testing blades right out of the quench you need to be prepared for the shock of seeing quite low numbers. Don't freak out like I did the first time. AEBL seams to have very high retained austenite and the hotter you go the more it seams to keep.
I have noticed that if you don't zero in on the optimum austenite temp you will experience a much higher chances of warps and bows. You will still get an odd one that will come out of the plates like a banana but the chances are greatly reduced. I'm guessing the warping is tied to the amount of retained austenite. I quench between quench plates and do it as smoothly and quickly as possible. I set the bottom plate across the back of my anvil and then lay the foil packet down and set the other plate on top and use a Irwin quick clamp to apply pressure. The trick is to leave the blade between the clamps for a decent amount of time. If you pull it out to soon even if it's cold it will bow. AEBL is rather soft right after a quench for a good amount of time.
After quenching I go straight to the cryo. Research seams to show that if you wait and don't cryo right away the austenite will stabalize over time.
A cold treatment is a MUST, if you don't hit the temp dead nuts then your left with a rather soft blade. I use liquid nitrogen because I use it for other alloys that need the -300° so why not use it for the AEBL. But you need to use dry ice with denatured alcohol at least. It does not seam to need any soak time in the cold bath but I do around 5-10min. After this you will have a bump in hardness. The amount depends on your starting hardness. I have seen it go from 50ish to 60-62rc. But 62-63 seams to be the max I can get out of the cryo even with my tweaked 1900° soak. But some times it can take some time to hit this hardness after the cryo for some odd reason.
You might be saying to yourself but wait how am I going to get 62rc after temper if I'm already there before tempering. This is where things get weird and I don't know the reason why but it's a head scratcher. I do the first temper at 300° for 2hrs. After this I test the hardness again and poof it's at 64-65RC. After this bump the temp up till you get the hardness your after.
You might notice from my timing that everything moves in one fluid motion so I'm able to process batches efficiently. While the oven is heating up I foil wrap all the blades. Then once the oven is ready I put one blade in the oven and let it soak for 10 min. Then it comes out and goes between the quench plates. While it's cooling I put the next blade in the oven. Then about 10 min later I remove the blade from the quench plates and pull the next blade from the oven and it goes between the quench plates. I open the foil pouch and remove the blade and it goes into the cryo. 10min later the process starts over and the blade is removed from the cryo to make room for the next blade moving down the line. I just keep moving all the blades one step every 10 min and before long all the blades are done and ready to temper. This process allows me to give each blade the attention and identical heat treat as the blade before and after it.
I don't claim to be an expert or a metallurgist I just know what I have discovered through testing. If I have made an error in my assumptions I would like to know about it and would like to understand why this steel acts the way it does.
