Alloy of iron and carbon in which the carbon content may range from less than 0.015% to slightly more than 2%. Adding this tiny amount of carbon produces a material that exhibits great strength, hardness, and other valuable mechanical properties. Carbon steels account for about 90% of the world's steel production. They are used extensively for automobile bodies, appliances, machinery, ships, containers, and the structures of buildings. Carbon steel, formerly made by the Bessemer, crucible, or open-hearth process, is now made by the basic oxygen process, or by an arc furnace.