High carbon steel, often called tool steel, contains from 0.60% to 1.70% carbon and can be hardened and tempered. Hammers, crowbars, etc. are made of steel with a carbon content of 0.75%; cutting tools such as drills, taps, reamers, etc. are made of steel with a carbon content of 0.90% to 1.00%. 

Generally, high carbon steel has high strength and is widely used in cutting, drilling, lathe, milling and other environments that require high hardness. Medium carbon steel Carbon steel with a carbon content of 0.25% to 0.60%. There are killed steel, semi-killed steel, boiling steel and other products. In addition to carbon, it can also contain a small amount of manganese (0.70% to 1.20%). 

According to product quality, it is divided into ordinary carbon structural steel and high-quality carbon structural steel. Good thermal processing and cutting performance, poor welding performance. The strength and hardness are higher than those of low carbon steel, while the plasticity and toughness are lower than those of low carbon steel. Hot-rolled and cold-drawn materials can be used directly without heat treatment, or they can be used after heat treatment. The quenched and tempered medium carbon steel has good comprehensive mechanical properties. The highest hardness that can be achieved is about HRC55 (HB538), and σb is 600-1100MPa. Therefore, among various uses of medium strength level, medium carbon steel is the most widely used, in addition to being used as a building material, it is also widely used in the manufacture of various mechanical parts. Mild steel, also known as mild steel, carbon content from 0.10% to 0.30% low carbon steel is easy to accept various processing such as forging, welding and cutting, commonly used in the manufacture of chains, rivets, bolts, shafts, etc.