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 that are 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.
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 organisations.
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