Ramping Oven from the Preheat to the Soak Temp

CDHumiston

CDHumiston

Well-Known Member
When I am doing a preheat for 15 minutes at 1500° and then ramping to 1925° I assume I leave the blades in the oven even though this rise in temp may take upwards of 30 minutes.

Is this correct?
 
I'm not sure which alloy you're using, but for AEB-L the preheat is 1725°F, then clamped in quench plates. I leave them in until oven reaches final temp. Hoss (Larrin's Dad) gave a good write up on his preferred method where he says to remove from oven during ramp up. Temper twice, first temper for 1 hour at 350F, 2nd temper for 2 hours – choose temperature based on Rc test prior to temper. The reason for 2nd temper is to covert even more RA.

Larrin has a good white paper on AEB-L here:
https://knifesteelnerds.com/2019/03/04/all-about-aeb-l/

Here's a short excerpt from the link:

For each temperature I held for 15 minutes prior to a plate quench, followed by either liquid nitrogen for 30-60 minutes, my household freezer for 30-60 minutes, or no cold treatment. As expected, the liquid nitrogen treatment cryogenic treatment led to the highest hardness, followed by the freezer, then room temperature. {snip}1925°F with room temperature, 1950°F with the freezer, and 1975°F with liquid nitrogen. The peak hardness was increased from 62.2 Rc with room temperature to 62.8 Rc with the freezer, to 64 Rc with liquid nitrogen. Higher austenitizing temperature means more carbon in solution for higher hardness.
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Also, if you bought your AEB-L from Aldo, it is supposedly Buderus X65Cr13 which requires a slight adjustment to the process when compared to real Uddeholm AEB-L. That came from one heat treater. Larrin also casually mentioned this bit about that steel and 13C26 needing slightly modified treatments in one of his articles.
 
KenH said:
I'm not sure which alloy you're using, but for AEB-L the preheat is 1725°F, then clamped in quench plates. I leave them in until oven reaches final temp. Hoss (Larrin's Dad) gave a good write up on his preferred method where he says to remove from oven during ramp up. Temper twice, first temper for 1 hour at 350F, 2nd temper for 2 hours – choose temperature based on Rc test prior to temper. The reason for 2nd temper is to covert even more RA.

Larrin has a good white paper on AEB-L here:
https://knifesteelnerds.com/2019/03/04/all-about-aeb-l/

Here's a short excerpt from the link:

For each temperature I held for 15 minutes prior to a plate quench, followed by either liquid nitrogen for 30-60 minutes, my household freezer for 30-60 minutes, or no cold treatment. As expected, the liquid nitrogen treatment cryogenic treatment led to the highest hardness, followed by the freezer, then room temperature. {snip}1925°F with room temperature, 1950°F with the freezer, and 1975°F with liquid nitrogen. The peak hardness was increased from 62.2 Rc with room temperature to 62.8 Rc with the freezer, to 64 Rc with liquid nitrogen. Higher austenitizing temperature means more carbon in solution for higher hardness.
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IIRC, Hoss said you "harden" AEB-L at 1750 first but no temper, then you go back into the oven at austenizing temp. That intermediate step is designed to eliminate the need to hold and soak for longer period of time at 1925-75. His ramping up process really requires 2 ovens. One at 1750 and one waiting at 1500 for the ramp up. IIRC, he said that if you only have one, just go straight up to 1900+ for the second round without the stop at 1500.
 
jmforge said:
Also, if you bought your AEB-L from Aldo, it is supposedly Buderus X65Cr13 which requires a slight adjustment to the process when compared to real Uddeholm AEB-L. That came from one heat treater. Larrin also casually mentioned this bit about that steel and 13C26 needing slightly modified treatments in one of his articles.
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I buy my steel from Alpha Knife Supply. This was my procedure and the results I obtained.

AEB-L. Preheat 1500° hold 15 minutes. Ramp to 1950° soak for 15 minutes. 1st 2-hour temper at 350° blades are 60 and 62.
2nd 2-hour temper around 340° blades finished at 61 and 62.5

I'm happy with the results with the equipment I have and my lack of experience.

Every day I learn something new, and I find the need for more equipment. Now I'm looking to buy a Dewar and Ln

This is just a hobby for me, and I've invested a lot of money in it. It does bring me satisfaction so I can't complain!

I do have Larrin's book, but it's hard to read...so scientific!
 
CDHumiston said:
I buy my steel from Alpha Knife Supply. This was my procedure and the results I obtained.

AEB-L. Preheat 1500° hold 15 minutes. Ramp to 1950° soak for 15 minutes. 1st 2-hour temper at 350° blades are 60 and 62.
2nd 2-hour temper around 340° blades finished at 61 and 62.5

I'm happy with the results with the equipment I have and my lack of experience.

Every day I learn something new, and I find the need for more equipment. Now I'm looking to buy a Dewar and Ln

This is just a hobby for me, and I've invested a lot of money in it. It does bring me satisfaction so I can't complain!

I do have Larrin's book, but it's hard to read...so scientific!
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The 1750F "pre-hardening" is Larrin's dad Devin's old family recipe recipe. Thje steel from Alpha is real AEB-L They get it direct from Voestalpine Precision Strip.
 
Didn't Larrin test the preheat/ramp/prequench business with AEB-L and conclude there was no measurable differences between that and just sticking it straight in a fully heated oven?

Ramping in industry is used to minimize distortion in much more complex parts. Since there is nothing complex about a piece of flat stock, distortion from uneven heating in an oven is pretty much a non issue. The only practical thing a preheat does is extend the amount of time that a piece spends at heat, which mostly puts more carbon in solution. If that is necessary, wouldn't a relatively shorter amount of time at full temp do the same thing?
 
Seems like Larrin did determine his tests didn't show any real difference. Hoss felt the 1750°F pre-heat perhaps made the grain a tad finer, and help with warping issues in final HT. AEB-L is such fine grain it's hard for me to tell any difference. Since Hoss said the pre-heat could be done one day, then final HT next day when I do the pre-heat I'll remove from oven, clamp in quench plates allowing oven to ramp up to 1975°F and stabilize, then remove blade from quench plates then to oven. Since I'm seldom doing more than 2 or 3 blades at a time it's not much extra trouble.

I don't always do the pre-heat and can't really tell any difference. BUT - Hoss is the real guru on AEB-L :)
 
KenH said:
Seems like Larrin did determine his tests didn't show any real difference. Hoss felt the 1750°F pre-heat perhaps made the grain a tad finer, and help with warping issues in final HT. AEB-L is such fine grain it's hard for me to tell any difference. Since Hoss said the pre-heat could be done one day, then final HT next day when I do the pre-heat I'll remove from oven, clamp in quench plates allowing oven to ramp up to 1975°F and stabilize, then remove blade from quench plates then to oven. Since I'm seldom doing more than 2 or 3 blades at a time it's not much extra trouble.

I don't always do the pre-heat and can't really tell any difference. BUT - Hoss is the real guru on AEB-L :)
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He said less time at high temp helped with grain size for sure. The warping part is good too. I have heard stories about the one downside to AEB-L is that it can get a bit wiggly in the quench.
 
but even Hoss said that if you didn’t have two ovens, and ramp time was more than a few minutes, just put it in at aus temp. Unless you did the preheat for grain pining. But that is easy you quench one or two blades from pre heat then put oven at aus temp and put blades in when at aus temp. Pre quench does seem to do more for higher carbide volume non-pm steel, but it doesnt get you to pm steel on the cheap
 
Do some testing for sure. Just because my oven works best at 1950F for freezer AEB-L, doesn't mean your temperature will be the same. You might be correct with 1940F showing and my oven is 10F reading too high. Make you up 3 or 4 coupons, wrap all in separate SS foil, and each heat each.
 
KenH said:
Do some testing for sure. Just because my oven works best at 1950F for freezer AEB-L, doesn't mean your temperature will be the same. You might be correct with 1940F showing and my oven is 10F reading too high. Make you up 3 or 4 coupons, wrap all in separate SS foil, and each heat each.
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The thing is, I never took the blades out of the oven between pre-heat and final austenizing temp. I pre-heated to 1500 put the blades in for 15 minutes and then ramped to 1950 and held for another 15 minutes. After plate quenching, I put the blades in the freezer for 1 hour. The temper was at 350 for the first 2 hours then cool to room temp and the second temper was at 340 for another 2 hours.

The blades came out great as far as I can tell without destroying one. That's why I want to do some testing.
 
This is from Alpha Knife Supply web site for AEB-L

AEB-L Heat Treat Information​

Preheat: Heat to 1,560° and equalize.

1,940°F Austenitize: Ramp to 1,940°F and hold at temperature for 15 minutes. Oil or plate or air quench as quickly as possible.
1,975°F Austenitize: Ramp to 1,975°F and hold at temperature for 5 minutes. Oil or plate or air quench as quickly as possible.

Temper: Temper immediately after hardening or cryo. Temper at least 2 times for two hours each time. Use the chart below to select the tempering temperature.

Cryogenic Treating: To get the most from AEB-L you must cryo. Cool to -95°F. No soak is required.

AEBL-TC.gif
 
That's pretty much what I do with AEB-L. Note above they say "1940°F" in the text, but show 1920°F in the chart. That's why testing is done, to determine which is best temperature in your oven.

I've read 1925F for no room temp, 1950F for freezer, and 1975 for -95F. Good luck and have fun doing the testing. I find that type of testing to be very informative and fun.
 
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