What to do when the number of knives exceeds quench capacity?

[MTBob]

I'm heat treating a number of knives using AEB-L with Alpha Knife Supply's HT recommendations. I want to do them (4 or 5 large blades) as one batch in the oven. Do any of you have experience extending the duration of the last heating hold point of 1975F? AKS recommends holding this last temperature for 5 minutes. I'm using big blocks of aluminum, but the number of knives in this batch will exceed the area available in the blocks for quenching.
So, can I pull out 1 or 2 knives - quench them (say 3-5 minutes) and then pull out and quench the next pair? The last two knives would be in the oven for a total of, say, 10-15 minutes (instead of 5).

 

[Gliden07]

You could always break them up into batches?

 

[KenH]

10 to 15 minutes shouldn't be a problem as HT'ing issues are more a matter of temperature rather than time. Larrin recommends holding AEB-L for 15 minutes. 1975°F if using Dry Ice or LN. 1950°F if using -5°F freezer, 1925°F if using room temperature. Here's Dr Larrin's article for HT'ing AEB-L.

All About AEB-L - Knife Steel Nerds

I've gathered all of the information I have on AEB-L steel, including its history, toughness, edge retention, ease in sharpening, and other properties.

knifesteelnerds.com

 

[Alden Cole]

Air hardening stainless seems to be less picky about how long you hold it at max temp than simple carbon steels (you don't need to worry about grain growth as much). I do a few AEB-L knives at a time, "quenched" one by one.

 

[fitzo]

The blades left in the furnace will be going below the quench temp every time you open the door. What is their final temp after a couple cycles like that? As seen in Larrin's article, 25F can make a difference. I like @Gliden07 's idea of doing them in batches. Pop the next pair in the furnace while the previous set is in the plates, rebound time plus 15 for the aus cycle. Gives a few minutes to chill the plates as needed.

Just my 2 cents. The lab rat in me tells me this could be a recipe for potential inconsistencies in HT.

 

[MTBob]

Hum... I knew you guys would come up with some good thoughts.
I was beginning to think just pulling them one at a time & quenching would work. But, the temperature will definitely drop each time a knife is pulled. (I wonder how low it would go - need to a test and see how low it goes). There's no doubt that after opening the oven door at the final soak point, 1975, that the temperature would decay below the previous soak point of 1950.
So, I'm inclined to not muck around with the unknown impact of temperature variations and, as suggested, I'll simply break the HT sequence into separate batches. This will also keep the Cryo and Tempering cycles more manageable.
Thanks for the comments!

 

[Taz575]

I ran into this issue this past week. I had 10 Magnacut blades and 2 AEB-L blades to heat treat and plate quench and a set of 4" x 18" x 1" aluminum plates. I did 2 blades at a time, so I would put 2 blades in, rebound, soak, quench in plates for 2 minutes or so (I just stood on the plates). I put the plates on the floor in front of my oven, so while standing on them, I added the next 2 blades to the oven. After a couple of minutes on the plates, I could handle the blades, so I put the plates into a water bucket to cool them down, removed the blades from the foil packets and put into another cold water bucket to get ready for cryo. By the time I was done with that and the plates were cooled down, it was almost time to pull the next blades out! It worked pretty well, but still took some time.

For the AEB-L, they were different thickness, so I put them both in the oven and did the thinner one first, then as soon as it was cool to touch, I put the plates into water, dried off quick and pulled the other blade out. It was only in there for maybe 5 more minutes than the thinner one and seems fine!

I want to get some other plates, like 8x12 or so, so it's easier to stand on and I may be able to get 4 blades into the plate at a time and not overload the plate cooling capacity. The 18" long plates are nice for longer blades, but a bit wobbly to stand on!