Steel is an alloy made by combining iron and other elements, the most common of these being carbon. When carbon is used, its content in the steel is between 0.2% and 2.1% by weight, depending on the grade. Other alloying elements sometimes used are manganese, chromium, vanadium and tungsten.
Carbon and other elements act as a hardening agent, preventing dislocations in the iron atom crystal lattice from sliding past one another. Varying the amount of alloying elements and the form of their presence in the steel (solute elements, precipitated phase) controls qualities such as the hardness, ductility, and tensile strength of the resulting steel. Steel with increased carbon content can be made harder and stronger than iron, but such steel is also less ductile than iron.
Alloys with a higher than 2.1% carbon content are known as cast iron because of their lower melting point and good castability. Steel is also distinguishable from wrought iron, which can contain a small amount of carbon, but it is included in the form of slag inclusions. Two distinguishing factors are steel's increased rust resistance and better weldability.
Though steel had been produced by various inefficient methods long before the Renaissance, its use became more common after more efficient production methods were devised in the 17th century. With the invention of the Bessemer process in the mid-19th century, steel became an inexpensive mass-produced material. Further refinements in the process, such as basic oxygen steelmaking (BOS), lowered the cost of production while increasing the quality of the metal. Today, steel is one of the most common materials in the world, with more than 1.3 billion tons produced annually. It is a major component in buildings, infrastructure, tools, ships, automobiles, machines, appliances, and weapons. Modern steel is generally identified by various grades defined by assorted standards organizations.
Famous quotes containing the word steel:
“Through joy and blindness he shall know,
Not caring much to know, that still
Nor lead nor steel shall reach him,”
—Julian Grenfell (18881915)
“I will be steel!
I will build a steel bridge over my need!
I will build a bomb shelter over my heart!
But my future is a secret.
It is as shy as a mole.”
—Anne Sexton (19281974)
“Man you ought to see his plans for allsteel buildins. Hes got an idea the skyscraper of the futurell be built of steel and glass. Weve been experimenting with vitrous tile recently... crist-amighty some of his plans would knock you out... Hes got a great sayin about some Roman emperor who found Rome of brick and left it of marble. Well he says hes found New York of brick an that hes goin to leave it of steel... steel an glass.”
—John Dos Passos (18961970)