steel
Carbon - iron alloy with carbon, machined and heat treated with a carbon content not exceeding 2,10%, which corresponds to the limiting solubility of coal in iron. Coal in steel is most commonly found in the form of pearl perlite. Sometimes, however, especially with higher carbon content, the cementite is present in the form of a ball surrounded by ferrite grains. According to the current standard, steel is defined as a material containing more iron than any other element, with a carbon content of less than 2% and containing other elements. A limited number of chromium steels may contain more than 2% of C, but 2% is a generally accepted value for steel and cast iron. The iron next to iron and carbon usually also contains other ingredients. The desired alloying components include mainly metals, usually chromium, nickel, manganese, tungsten, copper, molybdenum, titanium. Elements such as oxygen, nitrogen, sulfur and non-metallic inclusions, mainly sulfur and phosphorus oxides, are called impurities.