Calcium oxide is a necessary material for steelmaking

In iron and steel smelting, calcium oxide mainly serves as a slag former. Its core function is to remove impurities from iron ore and improve the purity and quality of steel.

1. Removing Gangue (Mainly Composed of SiO₂)

Besides iron, iron ore contains a large amount of non-metallic impurities such as silicon dioxide, which are called "gangue".

At high temperatures, calcium oxide reacts with silicon dioxide in gangue to form calcium silicate (CaSiO₃), which has a relatively low melting point.

Calcium silicate has a much lower density than molten iron, so it floats on the surface of molten iron to form "slag". Finally, the slag is separated, thus achieving the separation of iron from impurities.

The chemical reaction equation is: CaO + SiO₂ → CaSiO₃ (under high-temperature conditions).

2. Adjusting Slag Basicity to Optimize the Smelting Environment

The "basicity" of slag (the ratio of basic oxides to acidic oxides) is a key parameter in iron and steel smelting, which directly affects smelting efficiency and steel quality.

Calcium oxide is a strong basic oxide. When added, it can increase the basicity of slag and neutralize excess acidic substances in the furnace.

Appropriate basicity can enhance the desulfurization and dephosphorization capabilities of the slag. Meanwhile, it prevents acidic slag from eroding the furnace lining of the steelmaking furnace, thereby extending the service life of the furnace body.

3. Assisting in Desulfurization and Dephosphorization to Improve Steel Quality

Sulfur and phosphorus are harmful elements in steel. They can cause defects such as "hot shortness" and "cold shortness" in steel, so they must be removed during smelting.

Desulfurization: Calcium oxide can react with ferrous sulfide in molten iron to form calcium sulfide (CaS). Calcium sulfide dissolves into the slag and is discharged, reducing the sulfur content in steel.

Dephosphorization: In an alkaline slag environment, calcium oxide can combine with phosphorus oxides to form stable calcium phosphate (Ca₃(PO₄)₂). Similarly, it is separated along with the slag, realizing the dephosphorization of steel.