influences of non-metal impurities in steel productiondesulfurizer.
Phosphorus is brought into steel by ore. Generally speaking, phosphorus is also a harmful element. Although phosphorus can increase the strength and hardness of steel, it causes a significant decrease in plasticity and impact toughness. Especially at low temperatures, it makes the steel significantly brittle. This phenomenon is called "cold brittleness". Cold brittleness deteriorates the cold working and weldability of steel. The higher the phosphorus content, the greater the cold brittleness, so the phosphorus content in the steel is strictly controlled. By adding dephosphorizer or ferro phosphorus to adjust P content of the steel or iron. High-quality steel: P<0.025%; high-quality steel: P<0.04%; ordinary steel: P<0.085%.
The ability of ferrite to dissolve nitrogen is very low. When supersaturated nitrogen is dissolved in the steel, after a long period of time or subsequent heating at 200-300℃, nitrogen will precipitate in the form of nitrides, which will increase the hardness and strength of the steel, decrease the plasticity, and cause aging. . Adding Al, Ti or V to the molten steel for nitrogen fixation, so that nitrogen is fixed in AlN, TiN or VN, which can eliminate the tendency of aging.
Oxygen is a harmful element in steel. It naturally enters the steel during the steelmaking process. Although manganese, silicon, iron and aluminum are added for deoxidation at the end of the steelmaking process, it is impossible to remove it completely. Oxygen in the steel takes the form of FeO, MnO, SiO2, Al2O3 and other inclusions, which reduces the strength and plasticity of the steel. In particular, it has a serious impact on fatigue strength and impact toughness.