Deoxidizer Ferro Silicon

During the steelmaking process, in order to remove harmful impurities such as carbon and sulfur from the molten iron, oxygen molecules need to be added to the molten iron by blowing oxygen or adding oxidants during the smelting process. The oxygen content in the molten steel gradually increases and exists in the form of FeO in the molten steel. If the oxygen in the steel is not removed, the mechanical properties of the cast billet will be poor. If the molten steel has enough oxygen and is poured into the casting without removing it, it will bring casting defects to the casting, such as pores, slag holes, oxides, slag inclusions, black spots, pitting, etc. If it is minor, it will require argon arc welding repair or cold welding, and if it is serious, it will will be scrapped directly.

Preliminarily deoxidized manganese and silicon, national standard 99.7# electrolytic manganese flakes and national standard 75 silicon, 72# ferrosilicon can also be used.

Due to the strong affinity between silicon and oxygen, when ferrosilicon is added to steelmaking, the following deoxidation reaction occurs:

2FeO+Si=2Fe+SiO₂

Silica is the product of deoxidation. It is lighter than molten steel. It floats on the surface of the steel and enters the slag, thereby removing the oxygen in the steel. It can significantly improve the strength, hardness and elasticity of the steel, increase the magnetic permeability of the steel, and reduce the Hysteresis losses in transformer steel.

Deoxidation method one: diffusion deoxidation

The method of utilizing the diffusion behavior of oxygen in molten steel to transfer the oxygen in the molten steel into the slag to reduce the oxygen content of the molten steel is called diffusion deoxidation. The specific method is to spread the powdery deoxidizer on the slag surface after the thin slag is produced during the smelting reduction period. First, it reduces the oxygen content in the slag and destroys the balance of oxygen solubility between the slag and the molten steel. Oxygen must diffuse into the slag. Therefore, as the oxygen in the slag is continuously reduced, the oxygen in the molten steel will continue to diffuse into the slag, thereby reducing the oxygen content in the steel.

Commonly used powdered deoxidants for diffusion deoxidation include carbon powder, ferrosilicon powder, calcium silicon powder, aluminum powder, calcium carbide powder, etc. The C, Si, Al, Ca and other elements in these deoxidizers enter the slag layer to facilitate the reduction reaction of (FeO), such as:

The deoxidation products enter the furnace gas or are absorbed by the molten slag. Therefore, diffusion deoxidation does not pollute the molten steel. However, since diffusion deoxidation is performed at the interface between the slag and the molten steel, it takes a long time for oxygen to diffuse from the molten steel to the slag. Therefore, the production efficiency is low and the energy consumption is high.

Deoxidation method two: precipitation deoxidation

Precipitation deoxidation is to add lump deoxidizer (ferrosilicon lump, etc.) directly into the molten steel, and the deoxidizer reacts with (FeO) to cause deoxidation. Precipitation deoxidation is also called forced deoxidation. The elimination of deoxidation products in the precipitation deoxidation method affects the deoxidation effect. According to the formation time of deoxygenated products, deoxygenated products can be divided into:

These three types of deoxygenation products are collectively called endogenous deoxygenation products.

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