Iron

Abstract

Abstract Iron, the fourth most abundant element in the earth's crust, is the world's least expensive, most useful metal. Iron is alloyed with other elements for commercial applications. Iron‐bearing minerals of economic importance are hematite, magnetite, goethite, siderite, ilmenite, and pyrite. These ores can be beneficiated through crushing, grinding, magnetic separation, flotation, electrostatic separation, roasting, sintering, or pelletizing. Iron oxides in the form of pellet, lump, and/or sinter are fed along with coke and limestone into the blast furnace wherein the iron oxide is reduced and melted into hot metal (pig iron); the pig iron is further refined in an oxygen converter to make steel. New technologies are being developed as alternatives to the blast furnace for reducing iron oxide. These include direct reduction and direct smelting processes. Direct reduction is the process of converting iron ore into metallic iron without melting. Direct reduced iron (DRI) is used as a high quality feed material in electric arc furnace steelmaking, oxygen steelmaking, ladle metallurgy, blast furnace ironmaking, and foundries. Normally 90 to 95% of the iron in DRI is in the metallic form. The reduction of iron oxide proceeds from hematite to magnetite to wustite to iron. The most common reductants are reformed natural gas and coal. The main commercially proven direct reduction processes are discussed. Hot briquetted iron (HBI), a densified form of DRI, is more resistant to reoxidation and corrosion. In the foundry, ferrous scrap can be melted along with coke in a cupola or induction furnace to make cast iron. Cast iron can be classified into gray, white, malleable, or ductile iron. Economic, health and safety, and environmental issues are discussed.