Steel is the common name for a large family of iron alloys which are easily
malleable after the molten stage. Steels are commonly made from iron ore,
coal, and limestone. When these raw materials are put into the blast furnace,
the result is a "pig iron" which has a composition of iron, carbon, manganese,
sulfur, phosphorus, and silicon.
As pig iron is hard and brittle, steelmakers must
refine the material by purifying it and then adding other elements to strengthen
the material. The steel is next deoxidized by a carbon and oxygen reaction. A
strongly deoxidized steel is called "killed", and a lesser degrees of deoxodized steels are
called "semikilled", "capped", and "rimmed".
Steels can either be cast directly to shape, or into ingots which are
reheated and hot worked into a wrought shape by forging, extrusion, rolling, or
other processes. Wrought steels are the most common engineering material
used, and come in a variety of forms with different finishes and properties.