Definition of carbon steel and five elements in steel
May 31, 2022
Iron-carbon alloys containing less than 2% carbon are called steels. The five elements in carbon steel refer to the main components in the chemical composition, namely C, Si, Mn, S, P (carbon, silicon, manganese, sulfur, phosphorus). The second is that gas will inevitably be mixed in the steelmaking process, containing O, H, N (oxygen, hydrogen, nitrogen). In addition, in the sedation process with aluminum-silicon deoxidation, Al must be contained in the molten steel. When Als (acid-soluble aluminum) ≥ %, it also has the effect of refining grains. The effect of chemical elements on the properties of steel
1. Carbon (C): The carbon content in the steel increases, the yield point and tensile strength increase, but the plasticity and impact decrease. When the carbon content exceeds %, the welding performance of the steel deteriorates, so the low welding performance for welding is used. Alloy structural steel, the carbon content generally does not exceed %. High carbon content will also reduce the atmospheric corrosion resistance of steel, and high carbon steel in the open stock yard is easy to rust; in addition, carbon can increase the cold brittleness and aging sensitivity of steel.
2. Silicon (Si): In the process of steelmaking, silicon is added as a reducing agent and a deoxidizer, so the killed steel contains -% silicon. If the content of silicon in the steel exceeds that of silicon, it is an alloying element. Silicon can significantly improve the elastic limit, yield point and tensile strength of steel, so it is widely used as spring steel. Adding -% silicon to quenched and tempered structural steel can increase the strength by 15-20%. The combination of silicon and molybdenum, tungsten, chromium, etc. can improve corrosion resistance and oxidation resistance, and can manufacture heat-resistant steel. Low carbon steel with silicon content of 1-4% has extremely high magnetic permeability, and is used in electrical industry to make silicon steel sheets. An increase in the amount of silicon will reduce the weldability of the steel.
3. Manganese (Mn): In the process of steelmaking, manganese is a good deoxidizer and desulfurizer. Generally, the steel contains manganese -%. When more than % is added to carbon steel, it is considered "manganese steel". Compared with ordinary steel, steel not only has sufficient toughness, but also has higher strength and hardness, which can improve the hardenability of steel and improve the hot working performance of steel, such as 16Mn steel has a 40% higher yield point than A3. Steel containing 11-14% manganese has extremely high wear resistance and is used for excavator buckets, ball mill lining plates, etc. The increase of manganese content weakens the corrosion resistance of steel and reduces the welding performance.
4. Phosphorus (P): In general, phosphorus is a harmful element in steel, which increases the cold brittleness of steel, makes welding performance worse, reduces plasticity, and makes cold bending performance worse. Therefore, the phosphorus content in steel is usually required to be less than %, and the requirements for high-quality steel are lower.
5. Sulfur (S): Sulfur is also a harmful element under normal circumstances. It makes the steel hot brittle, reduces the ductility and toughness of the steel, and causes cracks during forging and rolling. Sulfur is also detrimental to weldability, reducing corrosion resistance. Therefore, the sulfur content is usually required to be less than %, and the high-quality steel is required to be less than %. Sulfur added to steel can improve machinability, commonly known as free-cutting steel.
