1. Classification according to chemical composition Carbon steel can be divided into low carbon steel, medium carbon steel and high carbon steel according to chemical composition (that is, carbon content).
(1) Low carbon steel is also called mild steel. The carbon content is from 0.10% to 0.30%. Low carbon steel is easy to accept various processing such as forging, welding and cutting. It is often used to manufacture chains, rivets, bolts, shafts, etc.
(2) Medium carbon steel: carbon steel with a carbon content of 0.25% to 0.60%. There are many products including killed steel, semi-killed steel, boiled steel and so on. In addition to carbon, it can also contain a small amount of manganese (0.70% ~ 1.20%).
According to product quality, it is divided into ordinary carbon structural steel and high-quality carbon structural steel. Thermal processing and cutting performance are good, but the welding performance is poor. The strength and hardness are higher than low carbon steel, but the plasticity and toughness are lower than low carbon steel. Hot-rolled materials and cold-drawn materials can be used directly without heat treatment, or they can be used after heat treatment. Medium carbon steel after quenching and tempering 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 with medium strength levels, medium carbon steel is the most widely used. In addition to being used as building materials, it is also widely used in the manufacture of various mechanical parts.
(3) High carbon steel, often called tool steel, has a carbon content from 0.60% to 1.70% 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%.
