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Conversation Between jimmontg and samuraistuart
Showing Visitor Messages 1 to 10 of 13
  1. 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.
  2. 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?
  3. 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.
  4. 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.
  5. samuraistuart
    02-21-2017 10:57 AM
    I had typed up a whole thing yesterday, but this stupid PM system limits to 1000 characters and I wasn't in the mood to chop it up and send it in pieces like I had done previously. I'll try to be brief.
    1. Flexibility has nothing to do with is determined solely by geometry. Hardness will determine how it fails. 2. You're looking up data for D2 developed for DIES...not edged tools. DO NOT TEMPER BEFORE CRYO!!!! 3. I've seen cryo data for O1 that says 400% increase in wear resistance. NO freaking way does cryo add 400% to wear resistance. WR is built into the steel with it's chemistry. You can't change that with cryo. 4. Sub zero (dry ice) will take care of RA in most steels, but some like the super complex SS need LN2 to get full RA conversion. 5. LN2 allows some super small eta carbide to precip upon tempering, but these carbides aren't about wear resistance, merely added cohesion between the martensite matrix and the primary carbides.
  6. jimmontg
    02-20-2017 12:28 PM
    What I wanted to mention Stuart and forgot is when I say my D2 filet knife is flexible, it is 59 RC+ hard flexible, but that is the triple temper and I even looked up my old notebook from Hinderliter about temper before cryo with D2 and it's on some HT instructions. One thing about D2, no overheating, put it into the oven when preheats are reached. If oven overshoots, take them out until proper temp is hit. Most D2 failure is overheat and tempers not right.
    My O1 blades come out where I want them too with flexibility. I sold an O1 filet knife for a $300 charter, because the skipper cleaned over 40 fish without once stopping to sharpen it and that is a lot of bones to cut through. Edge geometry is also in play here. I sharpen by hand, always have and always will. He filleted at least 40 more fish before touching up the edge with a small diamond I gave him.
  7. jimmontg
    02-19-2017 06:00 PM
    Hey Stuart I hear you, but I did have O1 crack on me when I went straight from quench to cryo which is why I do the pre-temper. The guys at Hinderliter were the ones that told me always to temper D2 before cryo or I might have my blade crack a year later. I'm going back to the 90s here when I basically did two steels, O1 and D2. At my last job Hinderliter was a huge resource for me and a small HT company around the corner from my job. I forged some too.

    D2 is a tricky steel, and I used to not cryo it at all, same for O1 until I read some scientific studies that dry ice is very useful and I spoke to my metallurgy teacher. I have an A.S. in engineering and many other classes besides including metallurgy, but not as many classes in heat treating. My O1 and D2 come out where I want them though and that's all that counts. Pardon my ramblings yesterday, I'm in a lot of pain and am taking morphine and so I tend to ramble.
  8. samuraistuart
    02-19-2017 11:49 AM
    Part 6...
    Hope you understand, I'm just trying to share knowledge. Not claiming anything. I'm no metallurgist....but I did stay at a Holiday Inn Express last night.
  9. samuraistuart
    02-19-2017 11:49 AM
    Part 5...
    With that said, I know it's easy for us to get used to doing it a certain way, and changing something that has been working for us is like fixing something that isn't broken. But if you find that there is no change in your end product by experimenting with different may be the techniques aren't actually THAT important to the end product! Which is why, when something works for us, we keep doing it. I started not knowing any of it, asking questions to Kevin and Robert, 2 metallurgists, and reading the literature till my eyes bled, then used those techniques when I started making knives. They work for me, but I thought I would pass it along, anyway.
  10. samuraistuart
    02-19-2017 11:48 AM
    Part 4...
    One other mentioned that you do a temper before cryo/sub zero. I know this has been done in the past, for strictly one reason, concern about distortion in the sub zero/cryo, and the snap temper will help that. However....why are we employing cryo/sub zero? It is to convert retained austenite that didn't get converted to untempered martensite at room temp post quench. What does tempering do, among other things? Stabilizes retained austenite. So if you are tempering BEFORE your sub zero/'re kinda negating the whole purpose of sub zero/cryo. Sub zero/cryo should ALWAYS be part of a continuous quench. That is to say, blade is at austenitizing temp, quenched down to room temp, then immediately into the dry ice or LN2. Then brought back UP to room temp, then tempered.

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