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Jerrod Miller

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Jerrod Miller last won the day on October 20

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About Jerrod Miller

  • Birthday 03/25/1984

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    Jerrod Miller 25
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    Near Spokane, Washington
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    Steel metallurgy, HEMA, forging (blades and otherwise).

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  1. You may want to reach out to specific colleagues of Prof. Verhoeven, rather than the school itself. I would imagine Christoph Beckermann worked with Verhoeven and thus may have a personal email address or something that could help. Last year when I spoke with Beckermann, he said he was going to be retiring soon (I think this is his last year), so he may even have some insight into contacting retired professors, too.
  2. It shouldn't need to be air tight. A tiny hole will allow pressure relief, but it isn't going to really suck the CO out very quickly. There will be a little bit of drive to mix the gas, but it isn't like you will be blowing air through the canister. So, a pinhole is a source of lost efficiency, but not a big one.
  3. I'd recommend 2 small changes. 1) I would go a bit cooler than non-magnetic for the normalization cycles. That is about 1414F, and I'd go down to at least 900F. 2) I would temper a second time after the first. Cool down to room temp between temper cycles (still air, water, whatever - doesn't matter).
  4. I would think it would help get it extra hot and soak it for a bit first. There are primary M7C3 carbides in there (meaning they form during solidification - right from the liquid), which are pretty big (comparatively speaking); they're long and skinny. You have to soak at pretty high temp to dissolve them, then the steel will move easier under the hammer and you will get smaller carbides forming at the end. The steel may have already done this from the mill, but perhaps not. ASM Heat Treater's guide says the forging range is 1905-2150 F, and I would say you should be closer to the top end. When done forging, do a soak at about 1200F to ensure carbides re-precipitate. Then HT as normal. Of course, you should absolutely test the results of this procedure to ensure it ends up doing what you want it to do for you. Note: Kevin Cashen recommends never dissolving carbides to a point you get more than 0.8% C in your matrix, but that is qualified with having small and dispersed carbides to begin with. If your carbides are big to begin with, then you need to dissolved them and create new smaller ones. It is certainly easier to not mess with the carbides if you don't need to.
  5. It depends on the application, often it is not best. Carbon generally reduces toughness. A case hardened piece will have been quenched. You can carburize the surface without quenching, too. The point of case hardening is to change the outer layer (case) to have a chemistry that will harden readily while the inner chemistry remains less hardenable. If one only heats/quenches the surface and not the center, that is surface hardening, which is also useful. Surface hardening can be done with flame or induction pretty readily. I suppose it could be done well with molten salt baths and other fun things, too. No. It will be brittle if you quench it without tempering, but if you carburize and slow cool it will be as soft as it is ever going to be. It will just have pearlite (and possibly ferrite, depending on chemistry) if slow cooled, just martensite if quenched. No. Carburizing is one step in case hardening. It is just the adding of carbon to the surface layer. You still have to quench from appropriate temperature (either straight from the carburizing cycle or a secondary heat treat cycle). Through hardening is not done with case hardening, and is in fact counter to the goals of case hardening. Differential hardening can be achieved via chemistry, like case hardening, or by temperature control, like surface hardening. This is also something to think about with differentially hardened blades. Hamons may look cool (beauty is in the eye of the beholder for things like this), but they definitely mean there is less hardened steel than a through hardened piece and you will eventually use up all the hardened steel before you would on a through hardened piece. This is why I personally do not like to see hamons anywhere near the edge. That is too much of a sacrifice of functionality for my tastes, but it isn't a big deal for others.
  6. @Rean Lubbe Have you seen this thread:
  7. That is a bad assumption, because it doesn't work like that. If something doesn't melt into the bath when making steel, it stays looking like a rock. When we add elements to steel, it looks like this: Ferromanganese https://en.wikipedia.org/wiki/Ferromanganese#/media/File:Ferromangan├Ęse_m├ętal.jpg Ferrochromium https://en.wikipedia.org/wiki/Ferrochrome#/media/File:Ferrochrome.JPG If that doesn't melt down, you will have a very bad and obvious inclusion, not a little shiny section. Anyone making anywhere near decent steel (and even placing making quite bad steel) will not have this happen. The entire bath is generally taken a few hundred degrees above melting point, and it is often held at hot enough temperatures while chemistries are verified and such that this just doesn't happen. What may happen is alloy segregation, where alloying elements are not evenly distributed in a sample. This can be caused by segregation during solidification, or from things like dissolving carbides (either primary carbides from solidification, or those present in powder metallurgy) and not giving sufficient time and temp to even out via diffusion. The elements are still dissolved in that they are part of the matrix. They just aren't evenly dispersed. Polishing alone isn't likely to tell you what you want to know. Etching is needed.
  8. I was just referring to these sections: Not this type of splotches: Exactly. It sounds to me like you desperately need to start polishing (and preferably etching) your samples and looking at them on the metallurgical microscope to learn what you are wanting to learn. Those are only intended to be used with polished samples anyway.
  9. Nope. This is just light reflecting back into the lens off the shiny parts that just so happen to have a bunch of small areas clos together at the same (or close enough to it) angle to all reflect together.
  10. You would still need a gating system, but it wouldn't need to look the same. You have to get the metal into the mold somehow, and that is a gating system. Generally speaking, the gating system is to be deigned to get the metal into the mold as quickly as possible while exposing the liquid metal to air (mainly oxygen) as little as possible. There are people that do the whole melt and pour in a fairly hard vacuum to reduce oxidization (mainly for things like difficult Ti parts). These set-ups can have gating systems that would generally be considered bad because they have removed the consideration of oxidization. So, depending on your set-up (gravity, pressurized, vacuum, etc.), you design your gating to get the metal in the cavity as fast as possible with the least amount of exposure to air, and with the ingate contacts located such that removing them and cleaning up the contacts is doable. In some situations you will also want to consider the heat of the metal coming in through the gates for flowing into thin sections as well as heat distribution for shrink/feeding purposes.
  11. Gating is the system/path that gets the metal into the actual part cavity of the mold. This would include the pour cup, sprue, runners, and ingates (AKA - gates) at a minimum, but one could also include vents. Typically the cavity sections of a mold will have gating, risers/feeders, and the part. Flow-offs, slag traps, pouring basins, and other flow management features would fall under the general "gating" category, but more specifically are typically considered part of the runners.
  12. Impact failure is drastically different compared to the slower loading of tensile testing. When you bend material you get an inside radius and outside radius of the bend. The inside radius is in compression, the outside radius is in tension. The outside radius is where the steel will fail. Impact testing is only really useful for situations like swords and axes. One could make an argument for chisels as they are struck by hammers/mallets, but they typically do not experience impact failure as tested by a Charpy Impact Test. Geometry factors are going to be huge players in such a test and will likely obscure any alloy/heat treat variables. No. Geometry is the big factor on force required for bending. Tensile strength directly relates to material failure. For example, a chisel that is 50% thicker than another will require a lot more force to bend, even if they have the exact same tensile strength. It would even take a lot more force to bend than the thinner one, even if the tensile strength was significantly lower than the thinner one (up to a point, of course).
  13. Charpy testing is not applicable to these. Tensile testing is.
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