High carbon steels, often called tool steels, contain from 0.60% to 1.70% carbon and can be hardened and tempered. According to product quality, it is divided into ordinary carbon structural steel and high quality carbon structural steel. Good hot working and cutting performance, poor welding performance. The strength and hardness are higher than low carbon steel, while the plasticity and toughness are lower than low carbon steel. Without heat treatment, directly use hot rolled material, cold drawn material, can also be used after heat treatment. The quenched and tempered medium carbon steel has good comprehensive mechanical properties. So in a variety of uses of moderate strength level, medium carbon steel is the most widely used, in addition to as a building material, but also a large number of used in the manufacture of various mechanical parts. Low carbon steel, also known as mild steel, has carbon content from 0.10% to 0.30%. Low carbon steel is easy to accept all kinds of processing such as forging, welding and cutting, and is often used in the manufacture of chains, rivets, bolts, shafts and so on.