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Number Of Blades To Put In Heat Treat Oven At Once

Discussion in 'Heat Treating' started by RussGen, Mar 20, 2020.

  1. RussGen

    RussGen New Member

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    Hi I just set up new even Heat lb18 oven and plan to heat treat some knives I've been working on. When forging I always Heat treated 1 knife at a time. What is the process of maintaining the temperature of the blades that remain in the oven when you remove and heat treat 1 knife at a time I have the automatic shut off when the door opens but I want to be sure to do this properly. I'm using 1084 so normally I would reach 1500 and shut off. But should I program it to hold at 1500 and keep returning the temperature of the knives to 1500. Thanks for any help
     
  2. Griff

    Griff Active Member

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    I’ve seen lots of makers have 3 to 4 knives in at a time, open the oven, quench one, close the door, quench the next, close the door, and so on etc.

    I’ve see makers who bind knives with mechanics wire and quench at the same time (if I were to do this method I would determine the total thickness of the bundle and heat-treat by the manufacturers recommendation of how many minutes per inch of thickness at said temperature, and only then maybe with a bundle of air-cure A2).

    Both of these concern me over raising the temperature of the quenchant if oil is being used. Let’s say the oil is a nice 120F for the first knife, by the forth it’s got to be too hot. So I guess separate quenches is the answer. Again, does a bundle do the same thing to the oil? And for a bundle what is the correct volume of oil needed?

    These questions and unsureness is why I still go one at a time lol. Sorry Russ, I wasn’t much help, just maybe arguing the side of one-at-a-time. But I would second that yes you would program the Even-Heat to stay at the correct Heat-treat temperature and make sure each knife gets a good soak. Trick then becomes not to over soak.
     
  3. Dave Hodson

    Dave Hodson New Member

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    I plate quench with aluminum plate so my volumes are restricted to what fits and the plate ability to dissipate heat. Generally I'm low volume so it's not an issue but a couple of times I've quenched a couple and left the rest in the oven. It only takes a couple of minutes to cool and the plates took three cycles with no problem (so six knives). The ceramic knife holder in the oven holds six knives so it worked out fine.

    I did run some 154 CM test blocks checking hold time against hardness. My numbers suggested holding the knives a little longer didn't affect the pre-temper hardness too significantly. In my case (Ovenheat oven and Wilson Hardness tester), holding at 1950 for 20min gave Rc 61.5 while 1950 for 45min gave Rc 61 (pre-temper). It was actually the temper temperature that had more impact on final hardness.
     
  4. RussGen

    RussGen New Member

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    Thank you Griff and Dave for all the good info_One blade at a time will be the way to go for me. Do you think it's okay to momentarily open the door while the elements are on? Tonight I did three normalizing on 1084 and I love the oven. So precise. I still love forging though and I'll do both. I'll wait to hear what you have to say about opening the door before I do my hardening and quenching.
     
  5. Dave Hodson

    Dave Hodson New Member

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    I don't see why it would be a problem but I don't know. I've always just let it run it's cycle.
     
  6. John Noon

    John Noon Well-Known Member

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    don't open the door a dozen times to view the pretty colors :whistling open and close then quench. I have run into a cold breeze hitting the ATP coated blade and having the coating fly off and lets say it was exciting. After that I put the blades in further back instead of right up front
     
  7. Dave Hodson

    Dave Hodson New Member

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    Good to know John - thanks. I rarely open the door but since I use foil it's never been an issue. Since I'm thinking of moving to ATP, I'll have to remember this.
     

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