Steel is composed mainly of carbon and iron, and also contains elements such as manganese, silicon, sulfur, and phosphorus. Steel is a collective name for iron-carbon alloys with a carbon content between 0.02% and 2.11%. Steel according to the carbon content can be divided into low carbon steel, medium carbon steel, high carbon steel; according to the quality can be divided into ordinary steel, high quality steel, advanced quality steel; according to the molding method can be divided into forged steel, cast steel, hot rolled steel, cold drawn steel.