It is used as deoxidizer and alloying agent in steel-making industry. In order to obtain steel with qualified chemical composition and ensure the quality of steel, deoxidation must be carried out in the final stage of steelmaking. The chemical affinity between silicon and oxygen is very large. Therefore, ferro silicon is a strong deoxidizer for steel-making, which is used for precipitation and diffusion deoxidation. Adding a certain amount of silicon in steel can significantly improve the strength, hardness and elasticity of steel. Therefore, ferro silicon is also used as alloying agent in smelting structural steel (containing silicon 0.40-1.75%), tool steel (containing sio.30-1.8%), spring steel (containing sio.40-2.8%) and transformer silicon steel (containing silicon content of 2.81-4.8%), ferro silicon is also used as alloying agent. At the same time, it is an effective new technology to improve the quality of steel, reduce the cost and save iron by improving the morphology of inclusions and reducing the content of gas elements in molten steel. It is especially suitable for the deoxidation requirements of continuous casting steel. Practice has proved that ferro silicon not only meets the deoxidization requirements of steelmaking, but also has the advantages of large ratio and strong penetration.