Real Steel: The Mystery of Steel—Magic and Magnetism

Real Steel: The Mystery of Steel—Magic and Magnetism

forge running at night in preparation for heat treating some knivesWhat is steel? An alloy of iron and carbon.

How could something so apparently simple be the subject of so much myth, mystery, and debate? The short answer is that steel does some very strange things that we still don’t fully understand, and it is exponentially tougher and harder than the iron, copper, and bronze we used prior to its discovery.

Magic and Molecular Strangeness

Many metals can be work hardened. Work hardening is the result of cold working a metal and can happen by repeated striking of the metal or by bending or machining, such as drilling, milling, or scraping. The hardening comes from a distortion of the crystalline structure of the metal, but no one knows for sure how that distortion makes the metal any harder.

You can see this yourself. Take a piece of copper wire (1/8” diameter or close to it should work fine) and bend it back and forth. You’ll notice two things: it gets warm, and it gets harder to bend. If you keep bending after it hardens, it experiences what is known as fatigue and eventually breaks. If you take that same piece of hard copper wire, heat it until it is red-hot, and then quench it in water, it becomes very soft again.

And that’s when things start getting strange…

Steel is Different

All steel, even steel with a low carbon content, can be work hardened. But starting at a carbon content of between 3–4% or more, steel can also be hardened by heat treatment. It does exactly the opposite of what non-ferrous metals—such as copper—do under the same conditions.

If you take a piece of simple carbon steel with a carbon content of 6% and heat it to critical temperature (more on that later) and then quench it in the appropriate liquid (different steels need different quenchants), it forms a crystalline structure called Martensite and is very hard and brittle. Once cooled to room temperature, that steel shatters like glass if it is struck or dropped.

But if you temper that piece of steel by re-heating it to temperatures between 300–500° F and holding it there for 1–2 hours, the steel retains much of its hardness and loses much of its brittleness. To soften—or anneal—steel, you must heat it to critical temperature and then cool it very slowly over the course of about 8 hours.

That’s the secret of properly heat treated steel—it’s brittle first and then softened to make it usable.

Critical Temperature and Magnetic Madness

Is carbon steel magnetic? Of course… not, well, sometimes. It is magnetic at normal temperatures, but critical temperature (about 1420° F for simple carbon steel) also makes steel non-magnetic. But it doesn’t become magnetic again until it drops to about 500° F.

Is it just me, or is that weird? In fact, that sort of change seems to suggest something for fantasy smiths: perhaps enchantments can be laid on steel only when it is non-magnetic? Or perhaps steel is resistant to enchantments except when it is being forged, requiring the enchanter to work closely with the smith.

Although there are solid theories, no one knows for sure, provably, why steel hardens when heat treated, or softens when cooled slowly, or becomes non-magnetic at 1420° F but doesn’t regain its magnetism until it cools to 500° F. When something behaves strangely, we humans love to speculate, and if no logical answer is found, we create myth. Steel has a lot of myths and legends…

I don’t have any better answers to these questions than anyone else. But I’m glad we have steel… I can make much better blades with it than with bronze!

17 thoughts on “Real Steel: The Mystery of Steel—Magic and Magnetism”

  1. Theres some great infomation as usaul Todd. Also some fantastic inspiration for GMs out there, especially for when creating backstories for weapons or other magical items made from steel.
    In your head how does the typical fantasy blacksmith use carbon and iron to create steel?

  2. Todd the Bladesmith

    @nermal2097 – I can tell you how it’s done in the real world, and I would encourage you to develope it from there. The carbon and iron alloying happens primarily during the smelting process. Typically in a small smelt charcoal is burned with the ore in an Earthen stack, and depending on the ore and the way the fire is maintained a bloom of iron or steel will form. I plan on writing more about smelting later, but this should be enought to get you started.

    @Ask a Shoanti – You’re most welcome. I’m having a lot of fun with this. Thanks!

  3. Interesting point– iron isn’t better than bronze, simply more abundant (there are few places to get tin in the ancient world), but *steel* is.

    I can’t imagine what went through early metalsmith’s minds to come up with the processes for working iron into steel, even for how to start metalsmithing…it’s not like there’s an example in nature to draw from.

    Great article!

    1. Vikings used to believe that by smelting in the bones of animals they killed the swords/axes/knives/etc would take on the spirit of the dead animal. Seemed to them to be true because their steel was better than everyone else’s. Now we know that it was the carbon in the bones that improved the steel.

  4. Todd the Bladesmith

    @Ben – Excellent point. Bronze is almost as hard as wrought iron and is more corrosion resistant. It also melts at a lower temperature so can be more readily cast. Yes, it boggles the mind when you realize most of these processes were discovered by accident. We could have been in caves eating bugs for a much longer time if not for dumb luck.

    @Tom Allman – You’re welcome.

    Thanks for the comments!

  5. This is really great stuff. As a hobby blacksmith, I have thought of the same thing myself. Its great to work in some real world coolness into your fantasy. I have just started a wizard that I plan on doing a lot of crafting with. This sort of thinking is exactly the kind of details I want to work into my character’s endeavors. Great article!

  6. Todd,

    I love your articles, and this one is, as usual, very interesting. However, I do have to take issue with one of your statements:

    “…but no one knows for sure how that distortion makes the metal any harder.”

    Pick up any introductory-level materials science textbook and it will explain exactly how metals become harder from cold working. We have the tools to look at individual atoms and molecules within a metal, and to measure the interactions between them, and we know what’s going on in those crystalline structures. The theory may not be perfect in every detail, but the general mechanisms are well understood.

    To explain the varying magnetic properties of steel at different temperatures, you would probably need a more advanced textbook, but that answer is out there, too. That being said, I really like the way you used the non-intuitiveness of it as a way to work magic into the picture.

  7. Todd the Bladesmith

    @Kiveya – I had never heard the song before, so I can’t say this reminds me of it, but I did look it up and I agree it’s pretty stupid… :)

    @Longtooth – It’s good to hear from a blacksmith. I find it to be second nature to forge a knife – I can do it without thinking about it, but I couldn’t forge a spoon or a leaf if there was a cash prize for doing it. I admire blacksmithing skills. I’m glad you like the article.

    @Lucas Jung – This is something I could talk about all day. We’re talking about hard and fast physical laws, so yes, you are absolutely correct, we know that if we do particular things to metal it will have measurable, predictable, and repeatable effects; both the material and our actions on it follow physical laws in a very precise manner. Gravity is a good analog to help explain my point. We know that an object falling in Earth’s gravity will accelerate at a rate of 32.2 feet per second per second until it reaches terminal velocity, and we know what an object with a known mass will weigh in Earth’s gravity with a very high degree of accuracy. But we can’t even agree (“we” being physicists, not you and I) on exactly what gravity is (sometimes described as a pulling force, sometimes a pushing force), much less on how it works. That doesn’t stop us however, from understanding its effects. IMO magnetism is as misunderstood as gravity.

    I think a quick and dirty way to explain my point is that in regard to the four fundamental forces we generally understand effects much better than we understand causes and that misunderstanding extends to other areas.

    Lucas, I don’t think we’re going to come up with a Grand Unification Theory on KQ, but that doesn’t mean we shouldn’t try… :)

  8. As the resident metal-finishing-engineer/chemist/heat-treat-expert at the plant where Craftsman hand tools are made, I find this explanation quite comprehensive and intriguing. It makes me think that I should take a look at other things I do in my daily life and try to apply them to my gaming . . . ;-)

  9. Todd the Bladesmith

    @Dustin G – I’m very happy to be getting responses from science minded folks like you and Lucas Jung. It’s good to get confirmation that giving a gaming/fantasy spin to a sometimes scientific subject can work and make us all think. We’ll be getting back to the weapons themselves soon so we can avoid getting too *real* or too dry.

    Thank you!

  10. I don’t know much about being a blacksmith or iron / steel for that matter, but I do know quite a lot about magnets especially electromagnets and how to make a solid state bar-magnet.
    If you line an anvil up to the north / south poles along with a bar of iron and hit it extremely hard with a hammer it will turn into a simple bar-magnet. The atom structure of the steel lines up with the poles and becomes a magnet. I don’t know, but maybe when heated to such high temperatures it changes the atomic structure and the atoms no longer line up with the poles, hence “No Magnet!”

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