It mainly refers to the steel with the mass fraction of carbon less than 2% and 11% and containing no specially added alloying elements. Sometimes also called plain carbon steel or carbon steel. Carbon steel is also called carbon steel, which refers to iron carbon alloy with carbon content less than 2 or 11%. Carbon steel generally contains a small amount of silicon, manganese, sulfur and phosphorus in addition to carbon. Carbon steel is classified by name, mainly including pig iron, carbon structural steel, high-quality carbon structural steel, low alloy structural steel, alloy structural steel, spring steel and bearing steel, tool steel, stainless steel and heat-resistant steel, etc