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Thread: Cold forging

  1. #11
    "My words are of iron..."
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    I'll be more specific.

    How does the annealing process remove the defects? Why doesn't normalizing do the same thing as annealing?

    When a steel is annealed, how does grain reduction occur?

    If pearlite is layers of ferric carbide, a very hard material, why is pearlite softer than martensite?

  2. #12
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    The added energy allows the molecules of the steel to start moving by breaking the bonds of the steel. Normalizing is a shorter lower energy process (energy is only added for the 10 minutes or so it takes to heat the blade) whereas a full anneal adds energy to the steel for hours.

    When annealed the grain realigns, and the pearlite transforms from its lamellar state into globs(spheroidizes). The amount of heat is what allows the atoms to rearrange. Pearlite forms when austenite is cooled slowly, martensite when cooled rapidly; martensite forms cutting edges. pearlite is part of annealed steel and forms in small sizes in tempered martensite.
    Last edited by Twalsh341; 06-05-2008 at 04:13 AM.

  3. #13
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    I was hoping you'd be more specific. I was under the impression that spherodizing was a very specific application of heat (energy) to a specific point for a set amount of time and that carbides (cementite) spherodized in a ferrite matrix because of those specific conditions. Something along those lines.

    I apologize for being repetitious: bainite forms from austenite, not martensite. I suppose that tempering any retained austenite has a chance of producing bainite but given the speed at which martensite forms, I'd estimate that chance as pretty slim without very tight thermal controls over time. If the heat treatment cycle was not precise, bainite could be found intermixed with martensite, but would likely to have formed first rather than secondarily. Bainite is a decomposition phase from austenite.
    Last edited by Mike Blue; 06-05-2008 at 04:14 AM.

  4. #14
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    Do you want to know what geometric stricture turns into what? thats as more specific as it gets.

  5. #15
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    Quote Originally Posted by Twalsh341 View Post
    Do you want to know what geometric stricture turns into what? thats as more specific as it gets.
    No, I'm back to my other questions. Please explain how, according to your assertion that pearlite is "layers of ferric carbide, a very hard material," and why pearlite is softer than martensite? This is a contradictory statement and I'm asking you to clarify the contradiction.

    I'm pointing out the contradictory statements and asking for factual resolutions of the contradictions. I have no wish to put any one person "on the spot."

    This is about information, not a person, that is not valid, clear and precise. Folks come to this forum to learn the right ways of doing things so they can make better razors/blades or understand claims made about how sharp steel items were manufactured. There may be many different ways to skin the cat, but they are not contradictory. It is not for you, or me, to propagate myths or magic or misunderstandings in this place.

    I'm asking questions because I want to understand what you understand. It is possible that I don't know something and I'm actively correcting my mistakes as I go. But when I find a contradiction, I want to also know where the difficulty began and where it got off track, so I don't make a similar mistake in my thinking. Then I can reset my known starting point and keep moving from a solid foundation. If I would make a contradictory claim and someone here heat treated a blade that was then ruined or failed in the hard world of the customer's parlor, my credibility would suffer. I have no wish to have that happen to anyone.

    I'm letting go of my end of this conversation because these things can be uncomfortable for everyone. But I've made my point.

  6. #16
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    I understand better where you are coming from, I apologize for anything uncomfortable I may have said.

    Back to the pearlite...
    Pearlite is a layered structure of ferrite and cementite. Cementite is iron carbide. Cementite forms at two different times, during the cooling of austenite, and during the tempering of martensite. The cementite forms pearlite or bainite when it layers with ferrite at different temperatures. The carbides in cementite provide the hardness, while the ferrite (basically pure iron with very little dissolved iron) is tougher.

    True damascus has been speculated to be visible grains of carbide and ferrite forged into patterns. Today we still don't know how such large layers of cementite and ferrite were made, possibly with alloying elements that increase the size of the grain structure.

    I suppose martensite and cementite have similar strength/brittleness, however the cementite when laminated with ferrite is less brittle than a fully martensitic steel.

    More thoughts on ferrite/cementite and Silver Steel

    When austenite is formed at the CT the amount of carbon in the structure is about .8%. Silver steel has a carbon content of about 1-1.2% I need to do further research, but I believe the excess carbon atoms form more carbide, producing a higher carbide to ferrite ratio id est a harder steel. As mentioned I need to research this further, but that seems like a plausible explanation of Silver Steel's extreme hardness.

  7. #17
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    Quote Originally Posted by Twalsh341 View Post
    ... True damascus has been speculated to be visible grains of carbide and ferrite forged into patterns. Today we still don't know how such large layers of cementite and ferrite were made, possibly with alloying elements that increase the size of the grain structure. ...
    I was really prepared to let this go. But it seems that understanding of my request for clear and correct information remains elusive to you.

    Read this article and any associated articles you want to search for by Dr. Verhoeven. Please.

    The Key Role of Impurities in Ancient Damascus Steel Blades

    Dr. Verhoven specifically mentions vanadium as an alloying element in wootz, aka original damascus steel. Vanadium should be well known to any metallurgist as a grain refining alloying element, NOT something that increases the size of the grain structure.

  8. #18
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    Quote Originally Posted by Twalsh341 View Post
    I understand better where you are coming from, I apologize for anything uncomfortable I may have said.
    No apology is necessary. I would ask you to take the same care in your answers as I do.

    Back to the pearlite...
    Pearlite is a layered structure of ferrite and cementite. Cementite is iron carbide. Cementite forms at two different times, during the cooling of austenite, and during the tempering of martensite. The cementite forms pearlite or bainite when it layers with ferrite at different temperatures. The carbides in cementite provide the hardness, while the ferrite (basically pure iron with very little dissolved iron) is tougher.
    What are the specific conditions for cementite to form in martensite? If you can answer this, you'll have answered part of your own thought about Silver Steel. I can live with the idea that pearlite is a lamellar structure with alternating ferrite and cementite, but how does cementite form into bainite? Isn't cementite a single phase crystal?

    More thoughts on ferrite/cementite and Silver Steel
    When austenite is formed at the CT the amount of carbon in the structure is about .8%. Silver steel has a carbon content of about 1-1.2% I need to do further research, but I believe the excess carbon atoms form more carbide, producing a higher carbide to ferrite ratio id est a harder steel. As mentioned I need to research this further, but that seems like a plausible explanation of Silver Steel's extreme hardness.
    I'm curious as to how the subject has now been changed to include ancient damascus and silver steel which were not parts of the original discussion. They are pleasant distractions however and two of my favorite metals.

    All that excess carbon (I think you mean hypereutectoid steel) has to go somewhere. But then that leads to another way of forming the specific carbide that you're speaking of. And, if we are speaking of a carbon steel like this, when raised to the CT and quenched, since you speak of extreme hardness, that requires a quench, where does the ferrite come from in that phase? Shouldn't it all be martensitic with other components?

    I do agree that more research is needed. I think your understanding is a little off. What are the references that you're using anyway?

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