Application and classification of carbon steel

The impurities and non-metallic inclusions of carbon structural steel are more, but it is easy to smelt, good process, cheap, and large production, (steel containing harmful impurities sulfur and phosphorus) is mainly used for the manufacture of engineering structural parts and mechanical parts with small forces. Therefore, it is widely used. Carbon structural steel is usually rolled into steel plates and various profiles (round steel, square steel, flat steel, Angle steel, channel steel, I-steel, rebar, etc.) for building structures such as plants, Bridges, ships, etc.

According to the quality of steel can be divided into ordinary carbon steel and high-quality carbon steel.

(1) Ordinary carbon structural steel, also known as ordinary carbon steel, has wider restrictions on carbon content, performance range and phosphorus, sulfur and other residual element content. In China and some countries, it is divided into three categories according to the guarantee conditions of delivery: Class A steel (Class A steel) is a steel that guarantees mechanical properties. Class B steel (Class B steel) is the steel that guarantees the chemical composition. Special steel (Class C steel) is a steel that guarantees both mechanical properties and chemical composition, and is often used to manufacture more important structural parts. China currently produces and uses the most A3 steel (Class A No. 3 steel) with carbon content of about 0.20%, which is mainly used for engineering structures. Some carbon structural steels also add trace amounts of aluminum or niobium (or other carbide forming elements) to form nitrides or carbide particles to limit grain growth, strengthen steel and save steel. In China and some countries, in order to meet the special requirements of professional steel, the chemical composition and properties of ordinary carbon structural steel are adjusted, and a series of ordinary carbon structural steel professional steel (such as bridge, construction, rebar, pressure vessel steel, etc.) has been developed.

(2) Compared with ordinary carbon structural steel, the content of sulfur, phosphorus and other non-metallic inclusions is lower. According to the different carbon content and use, this type of steel is roughly divided into three categories: 

① less than 0.25%C is low carbon steel, especially with carbon content of less than 0.10% of 08F,08Al, etc., because of its good deep drawing and weldability and is widely used as deep drawing parts such as automobiles, canning... Let's wait. 20G is the main material for making ordinary boilers. In addition, low carbon steel is also widely used as carburizing steel for machinery manufacturing. 

②0.25 ~ 0.60%C is medium carbon steel, which is mostly used in the tempered state to make parts of the machinery manufacturing industry. 

③ More than 0.6%C is high carbon steel, which is mostly used in the manufacture of springs, gears, rolls, etc. According to the different manganese content, it can be divided into ordinary manganese content (0.25 ~ 0.8%) and high manganese content (0.7 ~ 1.0% and 0.9 ~ 1.2%) two steel groups. Manganese can improve the hardenability of steel, strengthen ferrite, and improve the yield strength, tensile strength and wear resistance of steel. It is usually marked "Mn" after the grade of steel with high manganese content, such as 15Mn, 20Mn to distinguish it from carbon steel with normal manganese content.