Many kinds of steel, usually the number of alloying elements into low-alloy steel (concentration <5%), the alloy steel (content 5% to 10%), high-alloy steel (content> 10%); by mass into high-quality steel, alloy steel qualities; by characteristics and uses are divided into alloy steel, stainless steel, acid-resistant steel, wear-resistant steel, heat-resistant steel, alloy tool steel, bearing steel, alloy steel, spring steel, and special properties (such as soft magnet , magnet steel, non-magnetic) and so on. In addition to iron steel, carbon and a small amount of inevitable silicon, manganese, phosphorus, sulfur, it also contains a certain amount of alloying elements in steel alloying elements are silicon, manganese, molybdenum, nickel, Luo, alumina, titanium , niobium, boron, lead and rare earth in which one or several, this is called alloy steel. States alloy systems, with their own resources, production and use conditions vary, the development of nickel abroad previously, Ge and steel systems, the discovery of silicon, manganese, vanadium, titanium, niobium, boron, lead, rare earth Lord of the alloy system, alloy steel per cent of the total output of about a dozen, usually at the furnace in the smelting of steel by end-use can be divided into 8 categories, which are: alloy steel, spring steel, bearing steel, alloy tool steel, high-speed tool steel, stainless steel, heat-resistant steel can not afford leather, electrical silicon steel.