69 lines
4.0 KiB
Plaintext
69 lines
4.0 KiB
Plaintext
Notes on iron and steel
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Alloying iron with carbon is of huge importance, but in some processes
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the alloying is an implicit side effect rather than the product of
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explicit mixing, so it is a complex area. In the real world, there is
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a huge variety of kinds of iron and steel, differing in the proportion
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of carbon included and in other elements added to the mix.
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The Minetest default mod doesn't distinguish between types of iron and
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steel at all. This mod introduces multiple types in order to get a bit
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of complexity and flavour.
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Leaving aside explicit addition of other elements, the iron/carbon
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spectrum is here represented by three substances: wrought iron,
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carbon steel, and cast iron. Wrought iron has low carbon content
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(less than 0.25%), resists shattering, and is easily welded, but is
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relatively soft and susceptible to rusting. It was used for rails,
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gates, chains, wire, pipes, fasteners, and other purposes. Cast iron
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has high carbon content (2.1% to 4%), is especially hard, and resists
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corrosion, but is relatively brittle, and difficult to work. It was used
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to build large structures such as bridges, and for cannons, cookware,
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and engine cylinders. Carbon steel has medium carbon content (0.25%
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to 2.1%), and intermediate properties: moderately hard and also tough,
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somewhat resistant to corrosion. It is now used for most of the purposes
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previously satisfied by wrought iron and many of those of cast iron,
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but has historically been especially important for its use in swords,
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armour, skyscrapers, large bridges, and machines.
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Historically, the first form of iron to be refined was wrought iron,
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produced from ore by a low-temperature furnace process in which the
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ore/iron remains solid and impurities (slag) are progressively removed.
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Cast iron, by contrast, was produced somewhat later by a high-temperature
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process in a blast furnace, in which the metal is melted, and carbon is
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unavoidably incorporated from the furnace's fuel. (In fact, it's done
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in two stages, first producing pig iron from ore, and then remelting the
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pig iron to cast as cast iron.) Carbon steel requires a more advanced
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process, in which molten pig iron is processed to remove the carbon,
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and then a controlled amount of carbon is explicitly mixed back in.
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Other processes are possible to refine iron ore and to adjust its
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carbon content.
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Unfortunately, Minetest doesn't let us readily distinguish between
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low-temperature and high-temperature processes: in the default game, the
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same furnace is used both to cook food (low temperature) and to cast metal
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ingots (varying high temperatures). So we can't sensibly have wrought
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iron and cast iron produced by different types of furnace. Nor can
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furnace recipes discriminate by which kind of fuel is used (and thus
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by the availability of carbon). The alloy furnace allows for explicit
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alloying, which appropriately represents how carbon steel is made, but
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is not sensible for the other two, and is a relatively advanced process.
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About the only option to make a second iron-processing furnace process
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readily available is to cook multiple times; happily, this bears a slight
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resemblance to the real process with pig iron as an intermediate product.
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The default mod's refined iron, which it calls "steel", is identified
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with this mod's wrought iron. Cooking an iron lump (representing ore)
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initially produces wrought iron; the cooking process here represents a
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low-temperature bloomery process. Cooking wrought iron then produces
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cast iron; this time the cooking process represents a blast furnace.
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Alloy cooking wrought iron with coal dust (carbon) produces carbon steel;
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this represents the explicit mixing stage of carbon steel production.
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Additionally, alloy cooking carbon steel with coal dust produces cast
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iron, which is logical but not very useful. Furthermore, to make it
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possible to turn any of the forms of iron into any other, cooking carbon
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steel or cast iron produces wrought iron, in an abbreviated form of the
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bloomery process. As usual for metals, the same cooking and alloying
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processes can be performed in parallel forms on ingots or dust.
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