440c and aeb-l Heat Treat Question

[gutshot420]

I recently built a heat treat oven and it works great but it takes close to 2 hours to hit the 1880 I've been holding my 440c knives at. I read recently that preheating the oven is fine for aeb-l (which I am also using) and I was wondering how that same concept would effect 440c. The most detailed piece of information I've read on 440c has recommended slow heating to 1200, soaking for like 15 minutes (long enough for it to equalize), and then quickly bringing the temp to critical. My oven has 2- 240 volt kanthal elements but it still probably takes an hour and 15 minutes to get from 1200 to 1880. I wonder if I can change that with the PID controller... Anyway I would like to keep the steel in the oven for as short a time as possible, mostly to minimize the window for something to go wrong. Any guidance would be appreciated.

 

[Stacy E. Apelt - Bladesmith]

Check your ramp rate, it should be at 9999 for the step from 1200 to 1900. If that isn't the problem, then it may be because you wired the two elements in parallel, not series...or picked the wrong elements. Many people use the commonly found build instructions and schematic from British Blades, and they are for UK power, not USA power.

 

[gutshot420]

I believe you are right about my PID not being properly configured. The wiring and elements are definitely correct but I didn't take enough time to learn how the settings on the controller worked. Thank you much.

 

[gutshot420]

Update: I had 2 - 240 volt elements wired in series...which doubled the resistance and cut my amperage. I removed 1 of the elements and everything is working beautifully on 1 element. 15 minutes to reach 1500f.