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Thread: Through Case Hardening Low Carbon Steel To Acceptable Levels of Carbon- Possible?

  1. #1

    Question Through Case Hardening Low Carbon Steel To Acceptable Levels of Carbon- Possible?

    So this is something I'd never touch for a normal serious project, something that'd probably cost far more and be dramatically more difficult than just using good stock to start with, but it's part of a proof for something else. Essentially, I'm having to turn some Home Depot steel into a quality-ish sword, and there aren't any good options here; the best option, their "weldable structural steel" stock (theoretical carbon content resting between 0.15-0.50 percent, actual contents unknown and unknowable; described by some as, "the dog food of steel," due to the cheap reclamation process), is crap. Even if the carbon content in it were better, there's enough sulphur in it that it'd be pretty hot short no matter what you do. The only way to do anything halfway-respectable without any compositional alteration would require quenching it in cryogenic liquid (expensive and dangerous) or quenching it in mercury (very expensive, very illegal, and VERY dangerous). Obviously, there's a reason nobody respectable would do anything more than test projects with this garbage.

    However, for the sake of the project, I'm stuck trying to find a way to turn this stuff into something half-way decent, and I think I found something. Combine case-hardening, carbon migration, a few dozen heat cycles, and a carbonitriding finish, and I think you could wind up with something almost acceptable. Essentially, my thoughts are that you could case harden the steel as normal, heat it to the point that carbon migration diffuses some of the surface carbon into the steel, normalize, and then repeat for a few cycles until it's about the same content throughout, before finishing with a case hardening done with coke instead of charcoal (both to interfere with some of the sulphur in the steel and add some extra surface hardness). It'd be pretty irregular, the chemical composition would mean you'd have to use stock removal instead of forging, it'd be pricy to get it to work at all, and it might actually wind up being impossible to H&T properly (no idea there myself), but it might work.

    However, I say might for a reason: I can't find any actual research on anything remotely like this being done, at all. I know carbon migration between steels of similar alloys is a thing, that nitrogen and sulphur can interfere with each other in steel making, and the general effects of nitrogen on steel (along with the knowledge that nitrogen has been added in swordmaking before, albeit back in the days when they thought goat piss was a good quenchant because of "fire elemental" reasons), but I can't find any solid research on this kind of a process (probably because, as I said at the start, it'd be cheaper and easier to use a better grade of steel from the start).

    So, I suppose my question, reduced to simplicity: could this (admittedly complicated, expensive, and fairly stupid) process work at all, and would it possibly result in something that could make for a decent-ish (better than a SLO, not quite proper standards) blade steel? If not, am I simply missing something, or was the premise flawed from the start (besides the starting flaw)?
    Last edited by Nathaniel Jones; 08-18-2017 at 12:13 PM. Reason: Added the icon

  2. #2
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    Quote Originally Posted by Nathaniel Jones View Post
    Essentially, my thoughts are that you could case harden the steel as normal, heat it to the point that carbon migration diffuses some of the surface carbon into the steel, normalize, and then repeat for a few cycles until it's about the same content throughout,
    Same carbon content throughout would take a long time. Why not just case-harden? As long the carbon diffuses deeply enough so that you don't grind off the entire hard layer at the edge when sharpening, you'll have a hardened edge, and isn't that the goal?

    You can cut the steel into narrow strips, carburise, and then weld them back together (AKA piling).

    Quote Originally Posted by Nathaniel Jones View Post
    So, I suppose my question, reduced to simplicity: could this (admittedly complicated, expensive, and fairly stupid) process work at all, and would it possibly result in something that could make for a decent-ish (better than a SLO, not quite proper standards) blade steel? If not, am I simply missing something, or was the premise flawed from the start (besides the starting flaw)?
    Once upon a time, people considered wrought iron blades acceptable for swords. Swords used in battle, not SLOs. Swords with carbon content below 0.3% were still being made in the 19th century. So it all depends on what you mean by "better than a SLO, not quite proper standards".
    "In addition to being efficient, all pole arms were quite nice to look at." - Cherney Berg, A hideous history of weapons, Collier 1963.

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