According to the quality of carbon steel, it can be divided into ordinary carbon steel and high quality carbon steel.
(1) Ordinary carbon structural steel, also known as ordinary carbon steel, has a wide limit on carbon content, performance range, and phosphorus, sulfur and other residual elements. In China and certain countries, according to the guarantee conditions of delivery, it is divided into three categories: Class A steel (A steel) is steel that guarantees mechanical properties. Class B steel (B steel) is a steel that guarantees chemical composition. Special steel (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 (Group A steel) with a 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 nitride or carbide particles to limit grain growth, strengthen the steel, and save steel. In order to meet the special requirements of professional steel, the chemical composition and properties of ordinary carbon structural steel are adjusted, thus developing a series of professional steel for ordinary carbon structural steel (such as bridges, buildings, steel bars, pressure vessels, forgings). Steel, etc.).
(2) Compared with ordinary carbon structural steel, high-quality carbon structural steel has a lower content of sulfur, phosphorus and other non-metallic inclusions. Depending on the carbon content and the use, these steels are roughly divided into three categories:
Less than 0.25% C is low carbon steel, among which 08F, 08Al, etc. containing less than 0.10% carbon, is widely used as deep-drawing parts such as automobiles and cans due to its good deep drawability and weldability. …Wait. 20G is the main material for the manufacture of ordinary boilers. In addition, low carbon steel is also widely used as a carburized steel for machinery manufacturing.
0.25~0.60%C is medium carbon steel, which is used in the quenching and tempering state to make forgings in the machinery manufacturing industry.
More than 0.6% C is a high carbon steel, which is mostly used to manufacture springs, gears, rolls, and the like. According to the difference of manganese content, it can be divided into two groups of ordinary manganese content (0.25-0.8%) and higher manganese content (0.7-1.0% and 0.9-1.2%). Manganese can improve the hardenability of steel, strengthen ferrite, and improve the yield strength, tensile strength and wear resistance of steel. Usually, the label "Mn", such as 15Mn, 20Mn, is added after the grade of the steel containing high manganese to distinguish it from the normal manganese content of carbon steel.