AEB-L Temper Question

i4Marc

i4Marc

Joined
Oct 19, 2011
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Ok, so this is what my heat treat looked like. Wrapped in foil with paper chip inside. Heat to 1560˚ in an Evenheat oven with a 5 minute hold. Ramp up to 1990˚ with a 15 minute soak. Plate quench between two pieces of 2" X 4" X 18" 6061 aluminum (or aluminium for you blokes across the pond). I stood on top of the plates as the blade cooled for 15 minutes. Yes, I know, way more time than necessary. Then open the foil pouch and into the dry ice/denatured alcohol sub-zero bath for 70 minutes. I know, more time than needed but I was watching a program. I let the blade come up to ambient temperature then into a preheated 325˚ oven, verified with a rack-type thermometer. It has been in for 2 hours. I am getting ready to go in for the second temper but I want to make sure I get close to my target of 61.5 Rc. Should my second temper be hotter? If so, what is your suggestion? It looks like, according to AKS chart, 61.5 should be around 375˚ with the sub-zero step. Any reason not to go with 375˚ for my next temper? This blade will be a chef knife. Can I safely go harder than 61.5Rc?
 
You could give it a 350 F temper and have it tested and if it is above your target hardness then increase the temp and give it another temper. Sort of like sneaking up on it. It's probably the best way to formulate the perfect recipe.
 
I would 2nd temper at 325F, better your chance at getting 61.5hrc. If it's micro chipping too easily, then temper +25F for 15 minutes until edge is stable.

Chance - because high percent RA will be there after blade cool to around 100F between aluminum plates. 2-3 minutes should be plenty long quench time to cool blade down, next dunk in water, then sub-zero right away. So that RA doesn't stabilized and or transformed into non-martensite structure (perhaps ferrite + m23C6). I don't know how thick your blade is but ramping from 1560 then 15 minutes soaked at 1990F. Ramp time between 1700F & 1990F + soak, which was quite long in the oven. This much time, most (if not all) carbides are dissolved, so you'll get a lower rc. High temp (600+F) temper will precipitate CrC (M7C3) and Fe3C, however your matrix now in the mid 50's rc zone.
 
The blade is approximately .08 thick. I guess I'm pulling the plug on this one and tossing it in the junk pile. Starting over again tomorrow. I want to do this right. Thanks.
 
I ht my baseline AEB-L (also 13C26 + 14C28N) knives (for perf comparison against experimental knives in same steel) as follow:

batch: 0.08" & 0.118" thickness 1.5" wide, 9" OAL - each wrap in ss foil (no saw dust or wood chips - too messy & balloon the foil envelope)

1. heat oven 2000F, wait 2 minutes.

2. put knife in, wait for temp back to 2000F, start soak time for ~5 minutes.

3. plate quench for 20 to 30 seconds depend on thickness - I do stand on the plates to keep blade almost straight (if warp from leaning in oven rack). at ~600F; with gloves, remove ss foil, straighten if needed. Dunk to water temperature. Dry.

4. into DI bath (cryo in LN2 for me) until no more gas evaporation - probably takes around 1-2 minutes. dunk in water to warm up.

5. into pre-heated 300F kitchen oven for 30 minutes. dunk in water. rc test - mine hrc around 63. increase temper temperature until 1 point higher than target rc (est 15-25F per hrc point).

* repeat step 2 to 5 for 2nd knife. while waiting/doing step 5.

6. 2x tempers 1 to 2 hr at target temperature.

My kitchen baseline knives ~62rc. Outdoor utility ~60rc.

ymmv :)
 
With regard to this HT process are we finding AEB-L to be a viable steel? edge retention etc
 
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