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Recently Finished Building My First Ht Oven.

Discussion in 'Heat Treating' started by Wuatt, Aug 11, 2021.

  1. Wuatt

    Wuatt New Member

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    Howdy everyone. So I finished building my first HT oven a couple days ago, and I got around to giving it its first run from room temperature to 1500F. I was expecting the oven to take anywhere from 30-40 minutes to get up to temp, but I ended up being absolutely blown away when it made it up and past 1500F in just 16 minutes and change.
    I thought maybe it was a fluke, so I left it for a couple hours with the door open so it came back down to room temperature and gave it another go to 1500F. This time it was a staggering 13 minutes up to temp, and just to make sure I wasn't getting a bad readout off the thermocouple I threw a bit of 01 tool steel I had lying around in for about 8-10 minutes or so, and when I brought it out sure enough it was non-magnetic (Not a perfect test I know, but decent enough).

    My inside dimensions on the oven is about 18" long, 7" wide and 6" tall.

    From what I've read online, this seems really really fast to get up to 1500F.

    I'd love to hear some other thoughts from people with more experience than me (Is it safe to heat up that fast, maybe something I did wrong?).
    And in the meantime I'll work on getting some pictures of the oven, and a video timing the oven getting to 1500F!

    Thanks in advance everyone!
     
  2. dancom

    dancom Dust Maker

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    Congrats! Very sweet to have a useful piece of equipment that you made yourself.

    How many watts you running? Getting to 1500°F seems to be a breeze. The last part of the climb to 2000°F is where the temperature rise appears like an inverse exponential curve.

    I published a curve on mine. 2100W, 0.4 cu. ft.

    [​IMG]

    Just add more power if you want things to speed up. ;)

    Dan
     
  3. Wuatt

    Wuatt New Member

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    Thanks for the reply Dan! and thank you, it was a really overwhelming project at times, but it feels amazing to have a working and useful tool in the end!
    I'm running around 3600w + or - a bit, and my volume is about 3.05 cu. ft.

    And just to confirm, it isn't unsafe or damaging to the oven to heat up quickly like this?

    Thanks!
     
  4. dancom

    dancom Dust Maker

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    Wow, 3 cu. ft. is enormous! Might be a mis-calc. I read it as:

    Volume = L x W x H or
    18"(L) x 7"(W) x 6"(H) or
    1.5 ft. x 0.58 ft. x 0.5" ft. = 0.435 cubic feet.

    This is close to mine in volume. Yours being about 50% more power, explains your speedy rise times.
    It would be great to plot a curve for your machine. I put a clock next to PID controller and took a picture every 10 minutes. Then I entered the values into a spreadsheet and plotted a graph.

    Not a problem with the rapid climb. However with some high alloy steel, if the steel is sufficiently thick it may require an equalization rest. This rest allows the steel to become the same temperature throughout. Otherwise the outside will be hotter than the inside. You'll see equalization steps in datasheets from Crucible et al for this reason. Example: "Preheat: Heat to 1400°F (760°C) Equalize." In general I use thinner steel, <3/16" and my oven temperature rise is slower, so I forgo the equalization step as the inside and outside temperatures of the steel are similar during the climb to soak temp.

    Good luck!

    Dan
     
  5. Wuatt

    Wuatt New Member

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    Yes, I re-did the numbers and I miss calculated big time! And that's awesome, I really appreciate the info and tips, it helps a ton to a newer maker like myself.
    Thanks a ton Dan!
     
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  6. dancom

    dancom Dust Maker

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    It would be great to see some pics of your build and learn how it's working. An oven like this takes a maker into the world of stainless steel and offering these can be a game changer, especially in the kitchen knife market.

    Dan
     
  7. Wuatt

    Wuatt New Member

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    I agree, I'm super stoked to get into the stainless steel kitchen knife market. I'm going to make a new thread hopefully tomorrow afternoon (I get off work relatively early) and I will share a bunch of different pictures along with some details on how I built it and a performance graph!
     

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