Heat treat discoloration

Discussion in 'Shop Talk - BladeSmith Questions and Answers' started by Chalet, Oct 15, 2020.

  1. Chalet

    Chalet Gold Member Gold Member

    467
    Aug 23, 2013
    Hello! I’m new to this but have always enjoyed knives. Took a class a year and a half ago with a friend and then did some traveling and after a couple of cross country moves and job changes, finally have a house and a garage and subsequently the tools and a place to try this more. Just looking to make simple unique tools to use and give away.

    I did do a search about this as well.

    My question is that after heat treating knives they’ve been coming out of the oil with this discoloration. They’ve been singing a file and are noticeably harder than the raw steel when done side by side. Is this indicative of something I’m doing wrong, or of the metal not hardening? On a finished knife it was gone once sanded but wanted to see if it was something I should fix. It’s 80crv2 heated in a small Atlas and dipped into warm canola oil.

    Thanks! I’ve been enjoying reading through here. There’s a lot of fun stuff to learn.

    https://i.imgur.com/NitR73j.jpg
    https://i.imgur.com/w3nXZYw.jpg
     
  2. Blackdirt cowboy

    Blackdirt cowboy

    152
    Oct 29, 2015
    Is that right out of the quench with nothing done to them? That doesn’t look bad at all if so. My knives come out of the heat treat completely black.
     
  3. Chalet

    Chalet Gold Member Gold Member

    467
    Aug 23, 2013
    That’s after tempering actually. But basically they didn’t look much different than that before tempering.
     
  4. Bill DeShivs

    Bill DeShivs KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Jun 6, 2000
    Heat treating discolors steel.
     
  5. Stacy E. Apelt - Bladesmith

    Stacy E. Apelt - Bladesmith ilmarinen - MODERATOR Moderator Knifemaker / Craftsman / Service Provider

    Aug 20, 2004
    Ignore the colors on a blade both after the quench and after tempering. They are not really indicative of hardness or damage.

    The "tempering colors charts" you find are for people who flame tempered tools like chisels and occasionally knife blades. This is a different process than an oven temper (which is a much better temper).
     
    Last edited: Oct 16, 2020
  6. scott kozub

    scott kozub Basic Member Basic Member

    703
    Jan 1, 2018
    Once you do the finish grinding all the color will be gone.
     
  7. JTknives

    JTknives Blade Heat Treating www.jarodtodd.com Knifemaker / Craftsman / Service Provider

    Jun 11, 2006
    Did I hear you right that your quenching these blades in oil while thy are still in the foil. Normally you do not foil wrap oil hardening blades. This way you get a nice fast even quench that’s not interrupted buy a foil envelope.
     
  8. Joshua Fisher

    Joshua Fisher KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    564
    Mar 27, 2018
    I don’t see anywhere that he said he had the blades in foil.
     
  9. Stacy E. Apelt - Bladesmith

    Stacy E. Apelt - Bladesmith ilmarinen - MODERATOR Moderator Knifemaker / Craftsman / Service Provider

    Aug 20, 2004
    Yeah, I think JT must have been reading a different thread. Regular quench and temper.
     
  10. Chalet

    Chalet Gold Member Gold Member

    467
    Aug 23, 2013
    Yeah I didn’t use foil. Thanks everyone! I’ll give them that brass rod test today mentioned in another thread. I just wanted to see if the lighter colors towards the edge were indicative of softer metal.
     
  11. JTknives

    JTknives Blade Heat Treating www.jarodtodd.com Knifemaker / Craftsman / Service Provider

    Jun 11, 2006
    Wow how did that happen, facepalm.
     

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