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Re-heat Treating.

Discussion in 'Heat Treating' started by Grahamm, Apr 16, 2017.

  1. Grahamm

    Grahamm Active Member

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    I had a stupid lapse in judgement and I am sure I ruined my treat on a piece of O1. I had the BBQ going so I got it red again, dunked in motor oil and it didn't take a good harden when I filed it. So I tried it again and got it hotter and used more oil and it's still not where I would like it.

    Tomorrow I will be doing a bunch of A2 blades so once I'm done I will drop the heat to 1450 or so, give it a decent soak and use some actual quenchant which I should have done in the first place but is there a limit to how many times you can heat treat it?
    Thanks
     
  2. dancom

    dancom Dust Maker Best Shop Tool

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    I'd just heat and re-quench it. I am no metallurgist, but my understanding is that apart from losing a very small amount of carbon each time, you can harden a piece of steel multiple times.
    @John Noon ?

    Dan
     
  3. Grahamm

    Grahamm Active Member

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    I figure if you can forge steel a bunch of times. A couple heats aren't gonna decarbonize it that much but like you say, I'm no metallurgist either. Gonna do it either way, just wasn't sure if it was a lost cause then I would start over. Thanks.
     
  4. Jester4t7

    Jester4t7 New Member

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    I would anneal, and then try hardening again.
     
  5. Mythtaken

    Mythtaken Staff Member CKM Staff

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    That's the nice thing about steel. You can redo the heat treat again and again. If you are concerned about the stress of repeated hardening cycles, you can, as @Jester4t7 suggests, anneal the blade, or at least do a normalizing cycle first.
     
  6. John Noon

    John Noon Active Member

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    motor oil is a wild ass guess if it might or might not work, someone might say yes it does for them but then you try and it fails. To many unknowns too rely on it when it is a cheap or cheaper to use Canola oil and heat to 130F (120F to 150F) before quenching.
    From the stuff I have worked with the engineers say repeat once then thermal cycle to get back to a good point before trying again. So basically quench - Fail - Quench - Fail - then normalize at least once. Check all the details to figure out why it failed before trying again.

    Now for the A2 steel that is air cooled and hang it up and hit it with compressed air or put between quench plates. No need to oil quench it at all but it is a good idea to use foil wrap or anti-scaling paint or clay
     
  7. Grahamm

    Grahamm Active Member

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    I
    I tested the blade I was worried about not being hard on a file test and it was 62 RC as well so I left it.

    The A2 in my KITH was wrapped in stainless wrap, double crimped, soaked about 45 mins at 1750 and then hit with the fan on the bottom and compressed air on top. Cold in about a minute. It's back in the oven right now at 700 for the first temper. The O1 is in my kitchen oven at 400 for a cycle. This is fun. Love learning about this stuff. Using the Heat Treating App from ITunes mostly but my buddy the machinist is also giving me good advice when he's not cramming long blades in a short oven:)
    Thanks.
     
  8. John Noon

    John Noon Active Member

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    you know that would make a funny video, put in knife and pull out a pretzel. Mind you I pulled a boner myself when I tried oil quenching a 15" long fillet knife in a 12" tank, brain said push it all in so the handle hardens.

    When I pulled it out I was so annoyed I folded it in half and started over :roflmao
     

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