A carbon steel. Carbon is about 0.05% to 0.70%, 0.90% up to the individual. Can be divided into ordinary carbon steel and high-quality carbon structural steel, carbon structural steel categories. The former contains impurities, low price, performance for less demanding areas, the majority of its carbon content of 0.30 percent, manganese does not exceed 0.80%, lower strength, but the ductility, toughness, cold deformation good. With few exceptions, for the heat treatment is generally not used directly. Made more of steel, shaped steel, steel and so on. Use a lot, a great amount, mainly for railways, bridges, all kinds of construction projects, manufacturing all kinds of metal to withstand static load without heat treatment of the important components and mechanical parts and general soldering parts. Quality carbon structural steel steel pure, less impurities, mechanical properties, and can be heat-treated before use. According to manganese content is divided into ordinary manganese content (less than 0.80%) and high manganese content (0.80% ~ 1.20%) groups. Carbon content of 0.25% or less, and more directly without heat treatment or carburizing, carbonitriding and other processing, manufacturing, small gears, shafts, piston pins, etc.; carbon content of 0.25% to 0.60%, a typical steel No. there 40,45,40 Mn, 45Mn, and many more after quenching, manufacturing all kinds of mechanical parts and fasteners, etc.; more than 0.60% carbon, such as 65,70,85,65 Mn, 70Mn, and many more as spring steel to use.