For more than a century, steel has been the most important metal in industry. By the turn of the twentieth century, steel had replaced its parent metal, iron, as the primary metal for heavy industries such as construction, railroads, and, later, the automobile and airline industries. The invention of Henry Bessemer's converter in 1856 was the true beginning of steel as a commercially viable material.

Steel is a malleable alloy of iron with carbon and other trace elements. It is made by carefully removing excess amounts of carbon from pig iron, which has about four or five percent carbon content, and adding the other trace elements. Carbon steel contains less than one per cent carbon. Steel has been known for about two thousand years. Even earlier, smiths worked meteoric iron, which usually contains a large portion of nickel and resembles stainless steel in its composition. In Sri...