The role of Al2O3,MgO, FeO+MnO in refining slag

The role of Al2O3 in refining slag
According to the CaO-SiO2-Al2O3 ternary phase diagram, as the content of Al2O3 in the slag increases within a certain range, the melting temperature of the slag decreases.
Increasing the content of Al2O3 in the slag can promote slagging and rapid slagging.
The reduced slag rich in Al2O3 has the characteristics of looseness and foam, and the reaction area is large, which can increase the oxygen ion activity in the slag.
On the other hand, in the reducing slag rich in Al2O3, calcium aluminate has a low melting point and has a strong adhesion to molten steel, which can quickly float out of molten steel; In addition, CaS can well wet calcium aluminate and float molten steel together, thereby reducing the content of inclusions in the steel.

Influence of MgO in slag on desulfurization
MgO is an alkaline substance and has a certain binding capacity with sulfur, but not as good as CaO. Its main function is to reduce aSiO2 in the slag and increase aCaO, thereby improving the desulfurization effect.
The disadvantage is that MgO increases the melting point of the slag, especially when the MgO content is greater than 6.0%-8.0%, the slag thickens rapidly, which is not conducive to the reaction.
The appropriate amount of MgO content in the refined slag can protect the magnesia furnace lining and reduce the melting process of the furnace lining to the slag.

The effect of FeO+MnO on slagging
Slag oxidation is the main factor affecting the desulfurization effect of slag.
When the FeO+MnO content is greater than 1%, the desulfurization efficiency will decrease significantly.
The FeO + MnO content in the slag is less than 1%, which can achieve a better metallurgical effect.
In furnaces with FeO + MnO content less than 1%, the desulfurization rate can reach 86%, and the sulfur distribution ratio can reach 120-150.