The principle of using quicklime as a fluxing agent in steel smelting
Steel smelting requires the use of a large amount of quicklime (mainly composed of calcium oxide CaO), which plays a key role as a fluxing agent. Its principle is mainly based on chemical reactions with substances in the furnace.
Iron and steel smelting requires the removal of impurities such as gangue and coke ash from iron ore, most of which are acidic oxides (such as SiO ₂, Al ₂ O3) with extremely high melting points that are difficult to melt when present alone. And quicklime can react with these acidic oxides to form low melting point compounds or solid solutions. For example, calcium oxide reacts with silicon dioxide to form calcium silicate, which has a melting point much lower than the original melting point of impurities. A slag with good fluidity can be formed at around 1300 ℃.
The formation of slag achieves the separation of slag and iron, ensuring that the slag can smoothly flow out of the furnace during the slag removal operation. Meanwhile, by adjusting the composition of slag, such as alkalinity and melting point, the speed and quality of steelmaking can be controlled. Taking converter steelmaking as an example, adding quicklime can adjust the alkalinity of slag, affect the progress of dephosphorization and desulfurization reactions, and improve the quality of steel.
In addition, quicklime also has the function of neutralizing acidic substances. During the steelmaking process, a large amount of gas and dissolved acidic substances are generated, which can corrode equipment and affect steel quality. Lime can neutralize these acidic substances, protect equipment, and improve steel quality.
Lime, as a fluxing agent, plays an irreplaceable role in steel smelting by reducing the melting point of impurities, adjusting the composition of slag, and neutralizing acidic substances.
