Iron & Steel
Refractories are essential to iron and steel production, providing thermal insulation, chemical resistance, and structural protection for high-temperature equipment. They are used throughout ironmaking and steelmaking processes, where temperatures exceed 1500°C and linings are exposed to molten metals, aggressive slags, and reactive gases.
Iron Production
Iron is one of the most abundant elements on Earth, forming much of the planet’s core and around 5% of the crust. It occurs mainly in mineral form and is rarely found as metallic iron. Commercial extraction typically requires ores containing at least 50% iron in deposits suitable for large-scale open-cast mining. The most important ores are haematite and magnetite, commonly found in banded iron formations. Major producers include China, Australia, and Brazil.
High-grade ores may be smelted directly, while lower-grade materials undergo crushing, washing, and sintering. Traditionally, iron is produced in blast furnaces by reducing iron ore with coke and limestone. Coke provides heat and reduction, while limestone acts as a flux, forming slag. The process yields molten iron, typically over 92% pure, which is cast into pig iron or transferred as hot metal for steelmaking. Slag and furnace gases are recovered and reused.
Direct Reduced Iron (DRI) offers an alternative route, producing sponge iron by reducing iron oxides with natural gas or coal-derived gases below the melting point. DRI is mainly obtained in electric arc furnaces and offers lower energy use and capital cost, though it is prone to oxidation and retains impurities requiring removal during steelmaking.
Steelmaking Processes
Steel is an alloy of iron and carbon and remains fundamental to modern industry, with global production exceeding 1.5 billion tonnes annually. Carbon content determines basic properties: low carbon steels contain up to 0.25% carbon, medium carbon steels 0.25–0.75%, and high carbon steels up to approximately 1.5%. Increasing carbon content improves strength but reduces ductility.
Alloying elements are added to tailor performance. Manganese improves strength and toughness, vanadium enhances fatigue resistance, cobalt supports high-temperature performance, and chromium combined with nickel produces corrosion-resistant stainless steels.
Most steel is produced in basic oxygen furnaces, where molten iron, scrap steel, and fluxes are processed in refractory-lined vessels. Oxygen injection oxidises impurities, removing around 90% of the carbon and producing liquid steel. Electric arc furnaces provide an alternative route, melting scrap steel alone or combined with pig iron or DRI using high-power electric arcs, offering greater flexibility and lower capital requirements.