| commit | author | age | ||
| 68b7bc | 1 | Notes on iron and steel |
| Z | 2 | ======================= |
| 3 | ||
| 4 | Alloying iron with carbon is of huge importance, but in some processes | |
| 5 | the alloying is an implicit side effect rather than the product of | |
| 6 | explicit mixing, so it is a complex area. In the real world, there is | |
| 7 | a huge variety of kinds of iron and steel, differing in the proportion | |
| 8 | of carbon included and in other elements added to the mix. | |
| 9 | ||
| 10 | The Minetest default mod doesn't distinguish between types of iron and | |
| 11 | steel at all. This mod introduces multiple types in order to get a bit | |
| 12 | of complexity and flavour. | |
| 13 | ||
| 14 | Leaving aside explicit addition of other elements, the iron/carbon | |
| 15 | spectrum is here represented by three substances: wrought iron, | |
| 16 | carbon steel, and cast iron. Wrought iron has low carbon content | |
| 17 | (less than 0.25%), resists shattering, and is easily welded, but is | |
| 18 | relatively soft and susceptible to rusting. It was used for rails, | |
| 19 | gates, chains, wire, pipes, fasteners, and other purposes. Cast iron | |
| 20 | has high carbon content (2.1% to 4%), is especially hard, and resists | |
| 21 | corrosion, but is relatively brittle, and difficult to work. It was used | |
| 22 | to build large structures such as bridges, and for cannons, cookware, | |
| 23 | and engine cylinders. Carbon steel has medium carbon content (0.25% | |
| 24 | to 2.1%), and intermediate properties: moderately hard and also tough, | |
| 25 | somewhat resistant to corrosion. It is now used for most of the purposes | |
| 26 | previously satisfied by wrought iron and many of those of cast iron, | |
| 27 | but has historically been especially important for its use in swords, | |
| 28 | armour, skyscrapers, large bridges, and machines. | |
| 29 | ||
| 30 | Historically, the first form of iron to be refined was wrought iron, | |
| 31 | produced from ore by a low-temperature furnace process in which the | |
| 32 | ore/iron remains solid and impurities (slag) are progressively removed. | |
| 33 | Cast iron, by contrast, was produced somewhat later by a high-temperature | |
| 34 | process in a blast furnace, in which the metal is melted, and carbon is | |
| 35 | unavoidably incorporated from the furnace's fuel. (In fact, it's done | |
| 36 | in two stages, first producing pig iron from ore, and then remelting the | |
| 37 | pig iron to cast as cast iron.) Carbon steel requires a more advanced | |
| 38 | process, in which molten pig iron is processed to remove the carbon, | |
| 39 | and then a controlled amount of carbon is explicitly mixed back in. | |
| 40 | Other processes are possible to refine iron ore and to adjust its | |
| 41 | carbon content. | |
| 42 | ||
| 43 | Unfortunately, Minetest doesn't let us readily distinguish between | |
| 44 | low-temperature and high-temperature processes: in the default game, the | |
| 45 | same furnace is used both to cook food (low temperature) and to cast metal | |
| 46 | ingots (varying high temperatures). So we can't sensibly have wrought | |
| 47 | iron and cast iron produced by different types of furnace. Nor can | |
| 48 | furnace recipes discriminate by which kind of fuel is used (and thus | |
| 49 | by the availability of carbon). The alloy furnace allows for explicit | |
| 50 | alloying, which appropriately represents how carbon steel is made, but | |
| 51 | is not sensible for the other two, and is a relatively advanced process. | |
| 52 | About the only option to make a second iron-processing furnace process | |
| 53 | readily available is to cook multiple times; happily, this bears a slight | |
| 54 | resemblance to the real process with pig iron as an intermediate product. | |
| 55 | ||
| 56 | The default mod's refined iron, which it calls "steel", is identified | |
| 57 | with this mod's wrought iron. Cooking an iron lump (representing ore) | |
| 58 | initially produces wrought iron; the cooking process here represents a | |
| 59 | low-temperature bloomery process. Cooking wrought iron then produces | |
| 60 | cast iron; this time the cooking process represents a blast furnace. | |
| 61 | Alloy cooking wrought iron with coal dust (carbon) produces carbon steel; | |
| 62 | this represents the explicit mixing stage of carbon steel production. | |
| 63 | Additionally, alloy cooking carbon steel with coal dust produces cast | |
| 64 | iron, which is logical but not very useful. Furthermore, to make it | |
| 65 | possible to turn any of the forms of iron into any other, cooking carbon | |
| 66 | steel or cast iron produces wrought iron, in an abbreviated form of the | |
| 67 | bloomery process. As usual for metals, the same cooking and alloying | |
| 68 | processes can be performed in parallel forms on ingots or dust. | |
