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  1. #11
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    There are a lot of these kinetically controlled processes. An extreme example is diamond spontaneously converts to graphite but it's so slow it basically doesn't matter. As for letting a freshly sharpened knife sit for a few days... Maybe they are looking to have some sort of patina begin to form so it is less reactive when they do get around to using it. Total speculation...

  2. #12
    Thanks for info .)

  3. #13
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    Quote Originally Posted by DevinT View Post
    It is about transforming the retained austenite into martensite.

    Time, subzero quenching, and artificial aging are all used to make the transformation. Austenite is a smaller phase then martensite. If the blade is straight and has retained austenite that then transforms to fresh martensite the blade will move or become crooked.

    Thanks Sean for the compliment. I'm probably faster than most. It's only taken me 33 years.

    Hoss
    So what are the ramifications of this for the O1 blades that I'm making? I HT at 1500º, then temper at 350º for an hour, generally twice. Is the O1 going to change over time? The first blade that I did I HTed after grinding and it warped, after it was completed I took the handle back off and tempered again with the blade clamped to a heavy file and it is now almost straight. All together that blade was tempered 4 times.
    What I am now wondering is what am I going to have 3 months from now?
    Spike C
    "The Buddha resides as comfortably in the circuits of a digital computer or the gears of a cycle transmission as he does at the top of a mountain."
    Pirsig

  4. #14
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    Lower austinetizing temperatures, faster heating rates, less soak times, subzero quenching, longer tempering cycles, faster quench rates can all reduce retained austenite.

    I recomend that you grind less before HT. Quench from 1475f after soaking for 5 min. Quench in heated oil. Temper immediatly following the quench. 2x for 2 hrs each time. It is also good to go as cold as possible after the quench. You can go into the freezer directly after the oil quench for an hour. Of course it is best to do a full sub zero quench in liquid nitrogen or dry ice with acetone.

    Hoss

  5. #15
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    I have stopped doing any grinding prior to HT on this last blade. I also did about 5 min. on the soak, but the temp was a bit higher. I'm confused about your comment regarding post quench, however. Tempering immediately after quench is what I'm doing, but where does the freezer fit in this sequence?
    Dry ice and acetone, eh? That must get the temp down pretty good!
    (When I was in the Army hospital in Japan after surgery, my temp went up to 106 and they packed me in ice and alcohol. Chills ya right down, boy howdy!)
    Spike C
    "The Buddha resides as comfortably in the circuits of a digital computer or the gears of a cycle transmission as he does at the top of a mountain."
    Pirsig

  6. #16
    Senior Member rockbox's Avatar
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    dry ice and acetone makes liquid hydrogen.
    "Insanity: doing the same thing over and over again and expecting different results." --Albert Einstein

  7. #17
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    Continous cool down is what you want. Then temper.

    Hoss

  8. #18
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    Quote Originally Posted by rockbox View Post
    dry ice and acetone makes liquid hydrogen.
    Huh? Did I miss something?

  9. #19
    Senior Member rockbox's Avatar
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    Quote Originally Posted by tk59 View Post
    Huh? Did I miss something?

    Oops! I meant liquid nitrogen.
    "Insanity: doing the same thing over and over again and expecting different results." --Albert Einstein

  10. #20
    Senior Member rockbox's Avatar
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    Quote Originally Posted by rockbox View Post
    Oops! I meant liquid nitrogen.
    I was wrong about that too. LOL,
    Edit:

    I guess its time for me to take a chemistry class again. Its been 20 years.
    "Insanity: doing the same thing over and over again and expecting different results." --Albert Einstein

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