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damasteel HT w/o cryo

Discussion in 'Shop Talk - BladeSmith Questions and Answers' started by HSC ///, Aug 10, 2018.

  1. HSC ///

    HSC /// KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Nov 7, 2012
    Am thinking about trying out a Damasteel, I do not have any cryo or dry ice setup or any experience with it.

    My quick research indicates that the RWL version doesn't require cryo - see below from the Damasteel guidelines -

    "Deep freezing is not necessary but completes the martensite transformation and increases hardness. Hold for approx. one and a half hour"

    anyone have any experience with hardening Damasteel? and without cryo?

    regards
    Harbeer
     
  2. samuraistuart

    samuraistuart KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Dec 21, 2006
    Hey there Harbeer, I have no Damasteel experience, but if their own guidelines say "completes the martensite transformation and increases hardness", I would at least use the dry ice. Stainless steels have a martensite finish temperature well below 0°F, and that's why sub zero (dry ice) or cryo (LN2) is used.
     
  3. Stacy E. Apelt - Bladesmith

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

    Aug 20, 2004
    As far as I know RWL and Damasteel both need dry-ice bath at a minimum, and cryo if you have it. The dry ice bath is merely a metal pan with a gallon of methanol/denatured alcohol (hardware store) and around 3 to 5 pounds of dry ice chunks. The alcohol can be reused for a long time. The Dry Ice is cheap and can be bought at many larger grocery stores as well as other places.

    You need a programmable HT oven that can do 1950-2000F, stainless HT foil, and a set of quench plates to do any stainless steel blade. A dry ice bath is also needed for almost all stainless steels.
     
    Ken H> likes this.
  4. DevinT

    DevinT KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    947
    Jan 29, 2010
    You can't achieve an optimal heat treat without a sub-zero quench.

    If you are stubborn enough to try it anyway, heat treat at the lower end of the aus range, probably 1925’f and put it in the freezer as fast as possible. (After the quench)

    Hoss
     
  5. Stacy E. Apelt - Bladesmith

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

    Aug 20, 2004
  6. HSC ///

    HSC /// KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Nov 7, 2012
    I'm not at all that stubborn :)

    thx, I'll go with the sub zero a try if I decide to give this steel a try.
    Hold for approx. one and a half hour, as noted on the HT sheet, is this correct?
     
  7. samuraistuart

    samuraistuart KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Dec 21, 2006
    Technically speaking, the blade only has to reach the Mf temperature (no soak really needed), as the conversion to martensite happens literally at the speed of sound once the temp is reached. This probably happens within 10 or 15 minutes. But I do a few hours.
     
  8. Stacy E. Apelt - Bladesmith

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

    Aug 20, 2004
    The linked HT info is a bit confusing. The "Deep Freezing" in the write-up says -80°C/-110°F, but the graph shows it at -18°C/0°F.
    The 0°F is a practical Mf for those without a dry ice bath or LN. It can be attained by an hour or two in a good home deep freezer.
    The -110°F temp is the dry ice bath, and will fully reach the Mf. At that temp, the transformation is done and any length of hold will not make more happen.
    Most folks just leave it in the bath until the bubbles stop, but 10 minutes will be fine.
    As I say regularly, once you reach 100% you can't get any more. I know that the term 100% is not the real martensite percentage, but it is all that will convert, so technically, it is 100% of convertible austenite.
    Tempering twice immediately after warming to room temp is important. You want the whole cooling curve to look like the graph in the link - drop to room temp, hold a few minutes to let it all get even, cool to either 0°F or -100°F, warm to room temp and put right in the oven.
     
    Last edited: Aug 11, 2018

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