Howdy folks,
Well, finally got a couple more blades forged, so now we're going to "thermal cycle" this big blade, as well as two more. The other two blades are both damascus, and I hope to be posting photos of them in the not-too-distant future. The heat treat oven is not a free energy device, so I like to do as many blades at one time as I can. I made a rack out of angle iron to hold blades in the oven, and it holds three. Of course the angle iron scales, so I got some stainless angle iron off of fleabay, but I haven't gotten around to making a rack out of it.
I used to use the forge to thermal cycle, but I wasn't getting the steel hot enough, so I kept getting alloy banding in my blades.
So, here's the way I thermal cycle now. I set the oven to run 4 cycles. First cycle is at 1600, then 1550, then 1500, then 1450. The high temperature of the first cycle serves to dissolve carbides, making sure that the carbon is moving like it should. The others refine the grain, and homogenize the structure. I take the blades out to cool after each soak at temp and check with a magnet to make sure the austenite has finished converting to something else. What it converts to depends on what alloys are in the steel.
This blade is L6, which, because of it's deep hardening nature, is kind of interesting to heat treat. One thing I noticed about L6 is, when letting it cool after the first cycle, it takes a long time (ten or fifteen minutes, sometimes) to regain magnetism. But as the cycles progress, it takes less and less time to get magnetic. This is because with each cycle, the grain size becomes smaller, and when the grain size gets smaller, the hardenability (depth to which the steel will harden) decreases.
The last cycle, I let the blades cool all the way to ambient, which makes it a normalizing cycle, then run an annealing cycle. Which goes like this: hold at 1300 for one and a half hours, cool at the rate of 50 degrees per hour to 1000 degrees, then cool to room temperature.
I hope I made all that clear. And didn't put y'all to sleep.

If you do want something clarified, just speak up and I'll do my best.
Here's a pic of my oven:
Here's a pic of the blade cooling down from the last cycle:
Tomorrow I start grinding.