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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

    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

    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

    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
  9. HSC ///

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

    Nov 7, 2012
    so @DevinT I guess I'm a little stubborn...
    I bought a bar of Damasteel and decided to test a coupon
    The exercise was primarily getting familiar with the higher temps of working with SS etc.
    Anyway, I ran the oven at 1925 F at 12 min and quenched in plates with fan air.

    First measure was 60 RC
    after 90 min freezer time it seemed to pick up a point at 61 Rc, I checked in 3 places.

    I do intend to get the dry ice setup....
    that's all I have to report

    [​IMG]

    [​IMG]
     
  10. Salem Straub

    Salem Straub KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Oct 20, 2008
    I have HT'ed a few damasteel blades, all forged integral chef knives. The first try I plate quenched, did Dryo, and ended up with 61 Rockwell after temper on my first blade. On that first one I went straight into the dry ice bath from plate quench, with no snap temper... it worked out well.
    However I've heard horror stories about doing that with dama, and then had it corroborated when some integral dama blades I forged for Nick Anger cracked right through the bolsters when he went to dryo with no snap temper.
    The next three I made were for a looming show and I could not afford to crack anything, so while I did go into dryo, it was after a 300 degree 1 hour snap temper. They tested about a half point lower IIRC... what I'd call 60-61 rather than a clear average 61.
    Not a direct answer to your question, but I'd assume that when at all possible it's best to sub-zero them- just thought I'd add my experience with/without snap temper to highlight that this stuff can blow apart if you're not careful. My theory is that there was still some trapped heat in the bolster area on Nick's pieces when he put them in the cold. When I did it I had blasted the bolster a lot with air while the blade was in the plates, thereby cooling it enough (seems to me.)
     
  11. javand

    javand

    Oct 17, 2010
    Salem, did you run a stress relieving cycle before austenizing? I've found it pretty crucial with high alloys (although it's beneficial to pretty much any steels IMO), even if they're just stock removal, in mitigating warp, and potential stress fractures when skipping snap temper. For instance, last night I was HTing S-110v, and though it's "annealed" it's was clearly decked off with relatively coarse grit with a blanchard or some other grinder, after annealing. I stress relieved one piece after sawing out a profile, and one I did not. The one I didn't stress relieve, even though it was still just flat stock without any bevels, warped like crazy after going into LN, after plate quenching it straight, only got worse after first temper. The stress relieved one, stayed straight. The warped one didn't break, but I wouldn't be amazed to find a crack at some point.
     
    Willie71 likes this.
  12. HSC ///

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

    Nov 7, 2012
    so finally got around to the Damasteel HT yesterday and so here's the primary thing that I found that's important to me. The steel requires a lot more finishing then I'm accustomed to...mirror polish suggested prior to etch to best reveal the contrast.

    However it grinds nicely and seems like a solid performer. This first blade I'll carry and try out for awhile.
    I HT two slipjoint blades and a spring.

    next time I might try to up the temp, I don't think my as quenched was as high as it could/should have been. I'm still very much learning my oven and as I do mostly laminated steel in a forge, I'm not using the furnace often,
    My final is 61RC

    I don't know that I'm ready to get a dewar and goto cryo/LN just yet but maybe in the future.

    as far as the sub-zero treatment, my container started leaking so I had to use the lid....

    I did a quick FC etch, I have muriatic acid which is the suggested etch method, but chose not to go that route on this blade.

    I grind pretty thin and this is thin, even the tip is very thin. However it feels stable. It took a nice edge with a 1000 grit waterstone.

    [​IMG]
    [​IMG]

    [​IMG]
    [​IMG]
    [​IMG]
    [​IMG]
     
    Last edited: Dec 23, 2018
    Mo2 and Josh Rider like this.

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