Iron

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Position of iron in the periodic table.
Iron.

Iron is a chemical element with symbol Fe and atomic number 26. It is a metal and a very common element in Earth's crust, after only oxygen, silicon, and aluminum. It can be naturally found in small quantities in a nearly-pure form from meteorites and telluric iron. Most iron is extracted from Iron ores which are quite abundant in the Earth's crust, requiring kilns or furnaces to extract usable metal. Humans started to master that process in Eurasia around 3000 BCE with the development of the bloomery furnace. The displacement of copper alloys by iron tools and weapons is considered to mark the transition from the Bronze Age to the Iron Age. In the modern world, iron alloys, such as steel, stainless steel, cast iron and special steels, have been by far the most common industrial metals because of their mechanical properties and low cost.

Uses

See also: Spear

Iron can be used as a crafting material for a spear's head.

Dependencies

(Weapons and tools)
(Other)

Types of Iron

I. Raw Materials and Manufacturing Intermediates

  • Iron Ore:
    • Achieved: Mined directly from the earth. Common forms include Hematite (Fe2​O3​), Magnetite (Fe3​O4​), Limonite (FeO(OH)⋅nH2​O), and Siderite (FeCO3​). Requires processing (crushing, washing, sometimes concentrating) before smelting.
    • Properties: Varies widely by ore type. Key property is iron content and the nature of impurities (gangue). Not usable as a metal in this state.
    • Uses: The fundamental raw material for all iron and steel production.
  • Direct Reduced Iron (DRI) / Sponge Iron:
    • Achieved: Solid-state reduction of iron ore (usually pellets or lump ore) using a reducing gas (like hydrogen, carbon monoxide, or natural gas) or sometimes solid carbon (coal) at temperatures below iron's melting point. Avoids the need for a blast furnace.
    • Properties: Porous ("spongy") solid iron with impurities (gangue) from the original ore. Iron content is typically high (90-97%).
    • Uses: Primarily used as a feedstock for electric arc furnaces (EAFs) in steelmaking. Can be an alternative to scrap metal or pig iron, especially where coking coal for blast furnaces is scarce.
  • Pig Iron:
    • Achieved: Smelting iron ore in a blast furnace with coke (fuel and reductant) and limestone (flux to remove impurities). Molten iron is tapped from the furnace and typically cast into ingots called "pigs".
    • Properties: High carbon content (typically 3.8–4.7%), along with silicon and other impurities. Relatively low melting point (1150-1200°C), brittle, not directly useful for structural applications due to brittleness.
    • Uses: Primary intermediate product. Re-melted and refined to produce steel or various types of cast iron.

II. Cast Irons (Generally > 2% Carbon)

  • Grey Iron:
    • Achieved: Slow cooling of molten iron with appropriate carbon and silicon content, allowing carbon to precipitate out as graphite flakes within the iron matrix.
    • Properties: Excellent machinability, good wear resistance, excellent damping capacity (absorbs vibrations), relatively low tensile strength and ductility (brittle compared to steel due to graphite flakes acting as stress risers). Good fluidity for casting complex shapes.
    • Uses: Engine blocks, cylinder heads, machine tool bases, manifolds, cookware (e.g., skillets), pipe fittings, decorative castings.
  • White Iron:
    • Achieved: Rapid cooling (chilling) of molten iron, often with lower silicon and higher chromium content, preventing carbon from precipitating as graphite. Carbon remains combined with iron as iron carbide (cementite, Fe3​C).
    • Properties: Extremely hard, brittle, excellent abrasion resistance, difficult to machine.
    • Uses: Wear surfaces (e.g., grinding mill liners, slurry pump housings, shot-blasting nozzles), raw material for producing malleable iron.
  • Malleable Iron:
    • Achieved: Producing white iron castings and then subjecting them to a prolonged heat treatment (annealing) process. This breaks down the brittle cementite structure and causes the carbon to form irregular nodules (temper carbon) within an iron (ferrite or pearlite) matrix.
    • Properties: Better ductility and toughness than grey or white iron, good machinability, shock resistance. Largely superseded by ductile iron but still has niche uses.
    • Uses: Automotive components (differential housings, steering gear components), pipe fittings, electrical hardware, small machine parts requiring some ductility.
  • Ductile Iron (Nodular Iron / Spheroidal Graphite Iron):
    • Achieved: Adding small amounts of specific elements (typically magnesium, sometimes cerium) to molten iron of appropriate composition just before casting. This causes the graphite to precipitate as spheres (nodules) rather than flakes.
    • Properties: Combines the casting advantages of grey iron with mechanical properties approaching those of steel (good strength, toughness, ductility, wear resistance, machinability). More impact resistant than grey iron.
    • Uses: Pressure pipes and fittings, automotive components (crankshafts, gears), heavy machinery parts, wind turbine components, axle housings. A very versatile cast material.
  • Compacted Graphite Iron (CGI):
    • Achieved: Similar to ductile iron production but with tighter control over additives (often Mg and Ti) to form graphite particles that are short, thick, and interconnected (worm-like or vermicular), intermediate between flakes (grey) and spheres (ductile).
    • Properties: Intermediate properties between grey and ductile iron. Higher strength and stiffness than grey iron, better thermal conductivity and damping than ductile iron. Good castability and machinability.
    • Uses: High-performance engine blocks and cylinder heads (where higher strength-to-weight ratio and good thermal properties are needed), exhaust manifolds.
  • Austempered Ductile Iron (ADI):
    • Achieved: Subjecting ductile iron castings to a specific heat treatment process called austempering (austenitizing followed by quenching in a salt bath at a specific temperature range and holding). This creates a unique microstructure (ausferrite).
    • Properties: Very high strength, good toughness, excellent wear resistance, good fatigue strength. Properties can be tailored by adjusting the heat treatment parameters.
    • Uses: High-strength, wear-resistant applications like gears, crankshafts, suspension components, agricultural and construction equipment parts, military applications. Represents a high-performance grade of cast iron.

See also

References

This article uses material from the Wikipedia article Iron, which is released under the Creative Commons Attribution-ShareAlike 3.0 Unported License (view authors). Wikipedia logo
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