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samuraistuart samuraistuart is offline

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Showing Visitor Messages 1 to 10 of 12
  1. samuraistuart
    02-22-2017 11:28 AM
    But, if you are using the secondary hardening tempers (1000F), these high temp tempers convert the RA for you without the need for cryo. BUT...doing the secondary hardening allows undesireable carbide precip..which makes that edge apex actually more unstable. Wear resistance does go up some slight slight bit....but at the expense of ACTUAL edge retention. I hope that makes sense. Email me if you like! thanks.
  2. samuraistuart
    02-22-2017 11:28 AM
    Back to the snap temper....if you understand why...then you'd never do a snap temper BEFORE sub zero or cryo. The ONLY reason I would do a "snap" temper is, as you have mentioned with the D2 sample, was worries concerning distortion. Yes, absolutely, the snap temper CAN most certainly help in this regard. is NOT ideal by any stretch. It is a matter of converting retained austenite, and this is done with a continuous quench from aus temp all the way down to -100F or -300F. Adding a snap temper in the middle of this continuous quench stabilizes this retained austenite, which is what we are trying to get rid of in the first place.
  3. samuraistuart
    02-22-2017 11:22 AM
    So when you take a steel that was cryoed, vs one that was NOT....what you are experiencing with the cryoed steel is added toughness to the edge...NOT wear resistance. "Toughness" of an edge apex is what allows "edge retention"....not exactly wear resistance. I think most are confused about this issue, especially industry, as they call edge retention "wear resistance", and this is not the case. I was confused at first. Wear resistance actually has limited application in knife steel. We can verify this with imaging after use, and abuse. The edge either rolls or chips....this is because of a lack of "toughness" NOT wear resistance. Wear resistance is confused with actual "edge retention", and are not the same thing by any means. It is "toughness" that allows an edge apex to remain, not wear resistance...for the most part. To say that wear resistance does NOT come into play in SOME applications would be naive of me.
  4. samuraistuart
    02-22-2017 11:18 AM
    Full on Cryo, LN2, not ONLY converts retained austenite which may be present, but ALSO allows the formation of super small "eta" carbides upon tempering. What this does is allow for a better "cohesion" between the carbides and martensite matrix. What does that mean? Added "toughness". It does NOT add wear resistance in any appreciable manner. I believe the confusion is in terminology here. Wear resistance comes by the primary carbides (a make up of the steel's chemistry).
  5. samuraistuart
    02-22-2017 11:16 AM
    About the dry I have never had a blade distort using dry ice at all. But that doesn't mean it doesn't happen. There are 2 different "cryo" treatments. "Cryo" is a term we use specifically as LN2 temps (-300F). "Sub Zero" is the term we use for dry ice temps (-100F) There is only ONE thing dry ice converts retained austenite in the steels that have retained austenite after the quench. It does NOT do a single other thing than RA conversion. Steels with LOTS of alloying, the Mf is below the sub zero dry ice will NOT convert all RA. D2 is a candidate for LN2. AEBL has it's RA converted with sub zero dry ice.
  6. samuraistuart
    02-22-2017 11:13 AM
    Thanks for your replies. If this can continue, would maybe be better thru email? I know it's difficult to wrap your head around the flex thing, but it is absolutely true. This is a known fact....flex has NOTHING to do with is simply a matter of geometry (thinner..more flex). BUT, again, how HARD the blade is will determine HOW it fails. It's simply a matter of physics, and is well known/documented/discussed among knife makers and metallurgists.
  7. jimmontg
    02-21-2017 09:48 PM
    Stuart, I was enjoying our conversation. One thing just jumped backed to my mind (& notes), the HT guy from Hinderliter said for long term stable D2 you should do a quick pre-temper before cryo, that was like 2005-6. There are a lot of makers that won't touch D2.(Ray won't)
    The dry ice came up for some 4140 steel in the 1st place I had welded and was machined, but had to be HT like RC55 hard. When I talk about HT advice I received b4 I always talk about knives, not machined parts. I have not oven HT'd a part since 10/08, but have done a lot of forging. They've learned a lot since 2006 about cryo. I know about Fisher's site & his opinions. Seen others as well & not all agree.
  8. jimmontg
    02-21-2017 01:26 PM
    Stuart I have access to a HT oven and LN now. I will put O1 directly from quench to LN, but as I have never had a D2 knife failure I will continue to do a short temper on it before going in the LN, it works what can I say? That O1 filet knife with CO2 cryo is something I never did before without plain making it harder. Just saying, make it too hard and flexibility goes too. Cryo helped in that regard and it was more abrasion resistant than any noncryo O1 blade I ever did, again w/o making it too hard. Maybe that 1 O1 knife cracked cuz all the heat was pulled from 1 side for too long?
  9. jimmontg
    02-21-2017 12:29 PM
    I never cryo'd any steels btw until I was made a HT. Hinderliter faxed me excerpts from some scientific journals and instructions for the dry ice. One thing I read more than once that directly affects knives, cryo affects not just hardness, but toughness. My cryo'd blades were always tougher than w/o cryo which is why I say it affects flexibility. There is plenty of science behind that. We've had HTers telling us different things is all. I've noticed a lot of that. Been told dry ice is a waste of time and only LN works.
  10. jimmontg
    02-21-2017 12:08 PM
    I find it hard to believe flexibility has nothing to do with hardness. No I was looking at info for knives from HTers and for D2 a temper was called for before cryo, but not all said so. A short temper, but a temper nonetheless. Maybe not for O1 but you never had a blade snap and pop up less than a minute after being placed on dry ice, I have and there was nothing wrong with HT and quench beforehand exactly like 3 other blades I had already done. We had a 2' wide by 2.5' deep by 4' quench tank. to match a 2' deep oven, oil didn't overheat. Dry ice does have an effect if it lasts 3 days. Never said dry ice was as good as LN just said it made my knives measurably better and it did.

About Me

  • About samuraistuart
    San Antonio Texas
    anything redneck
    self employed lawn care
    Real Name
    Stuart Davenport


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  • Last Activity: 01-28-2019 12:27 PM
  • Join Date: 12-05-2012

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