Smelting

The process by which a metal is obtained from its ore, either as the element or as a simple compound, usually by heating beyond the melting point, ordinarily in the presence of reducing agents such as coke or oxidizing agents such as air. A metal whose ore is an oxygen compound (e.g., iron, zinc, or lead oxide) is heated (reduction smelting) in a blast furnace to a high temperature; the oxide combines with the carbon in the coke, escaping as carbon monoxide or carbon dioxide. Other impurities are removed by adding flux, with which they combine to form slag. If the ore is a sulfide mineral (e.g., copper, nickel, lead, or cobalt), air or oxygen is blasted through (matte smelting) to oxidize the sulfide to sulfur dioxide and any iron to oxide slag, leaving the metal.