Round steel



Classification by steel quality
According to the quality of 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 wide restrictions on carbon content, performance range and content of phosphorus, sulfur and other residual elements. In China and some countries, it is divided into three categories according to the guaranteed conditions of delivery: Class A steel (Class A steel) is steel that guarantees mechanical properties. Type B steels (Type B steels) are steels with guaranteed chemical composition. Special steel (C-type steel) is a steel that guarantees both mechanical properties and chemical composition, and is often used to manufacture more important structural parts. China produces and uses the most A3 steel with a carbon content of about 0.20% (Class A No. 3 steel), which is mainly used for engineering structures.
Some carbon structural steels also add a small amount 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 China and some countries, in order to meet the special requirements of professional steel, the chemical composition and properties of ordinary carbon structural steel have been adjusted, and a series of professional steel of ordinary carbon structural steel (such as bridges, buildings, steel bars, steel for pressure vessels, etc.).
(2) Compared with ordinary carbon structural steel, high-quality carbon structural steel has lower content of sulfur, phosphorus and other non-metallic inclusions. According to the different carbon content and use, this kind of steel is roughly divided into three categories:
① Less than 0.25% C is low-carbon steel, especially 08F, 08Al, etc. with carbon content less than 0.10%, which are widely used as deep-drawn parts such as automobiles and cans because of their good deep-drawing and weldability. ……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 quenched and tempered state to make parts in the machinery manufacturing industry.
③More 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 higher 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. Usually, "Mn" is added after the grade of steel with high manganese content, such as 15Mn, 20Mn, to distinguish it from carbon steel with normal manganese content.




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