In the converter, the removal of phosphorus is relatively sufficient, because the conditions are favorable, the alkalinity is high, the (FeO) content is high, the slag amount is large, and the slag fluidity is good, but in the tapping, with the addition of the deoxidizer.

The oxygen in the slag can be reduced, and the SiO2 and AhO3 are increasing, that is, the alkalinity of the slag is decreasing, and the (FeO) is decreasing. 

Therefore, under the action of the strong reducing agent SiAL, the unstable P2O5 in the slag is quickly reduced. Enter the molten steel.