Silicon and steel can react under certain conditions. Normally, there is no direct chemical reaction between pure silicon and ordinary carbon steel (i.e., steel containing a small amount of carbon).
However, at high temperatures and pressures, silicon can react with certain components of steel. For example, in some high-temperature industrial processes, silicon may react with elements such as iron and carbon in steel to form some compounds.
In addition, in specific industries, silicon steel (also known as electrical silicon steel) is a special type of steel in which silicon is intentionally added to improve the magnetic and electrical capabilities of the steel. This type of silicon steel is widely used in the manufacture of electrical equipment such as transformers and motors.
For many materials in carbon steel, there is less than 0.5% Si, which is generally brought in as a result of the steelmaking process as a reducing and deoxidizing agent.
Si can dissolve in ferrite and austenite to improve the hardness and strength of steel, and its role is second only to phosphorus, stronger than manganese, nickel, chromium, tungsten, molybdenum, vanadium and other elements. But the silicon content of more than 3%, will significantly reduce the plasticity and toughness of steel. Silicon can improve the elastic limit, yield strength and yield ratio (σs/σb), and fatigue strength and fatigue ratio (σ-1/σb) of steel. This is the reason why silicon or silicomanganese steel can be used as a spring steel grade.
Effects of silicon on steel properties:
Silicon reduces the density, thermal and electrical conductivity of steel. It induces ferrite grain coarsening and reduces coercivity. There is a tendency to reduce the anisotropy of the crystals, so that magnetization is easy, the magnetoresistance is reduced, and can be used to produce electrical steel, so the hysteresis loss of silicon steel sheet is lower. Silicon can improve the magnetic permeability of ferrite, so that the steel sheet in a weaker magnetic field has a higher magnetic susceptibility. However, silicon reduces the magnetic susceptibility of steel in strong magnetic fields. Silicon reduces the magnetic ageing effect of iron due to its strong deoxidizing power.
When steel containing silicon is heated in an oxidizing atmosphere, a thin film of SiO2 will form on the surface, thus improving the steel's resistance to oxidation at high temperatures.
Silicon induces the growth of columnar crystals in cast steel, reducing plasticity. Silicon steel if heated when cooling faster, due to the low thermal conductivity, the steel internal and external temperature difference is large, and thus fracture.
Silicon can reduce the welding properties of steel. Because of the combination of oxygen with the ability of silicon is stronger than iron, easy to generate low melting point silicates in welding, increasing the mobility of slag and molten metal, causing spattering phenomenon, affecting the quality of welding. Silicon is a good deoxidizer. Deoxygenation of aluminum with a certain amount of silicon, as appropriate, can significantly improve the rate of deoxygenation. Silicon in the steel would have had a certain amount of residue, which is due to the ironmaking steelmaking as raw materials brought in. In boiling steel, silicon is limited to <0.07%, and when intentionally added, ferrosilicon alloy is added during steelmaking.
