When smelting ferromolybdenum, the rate of self-heating reaction is very fast, and as soon as the reaction is over, the furnace temperature decreases quickly.
In order to maintain the fluidity of materials in the furnace and ensure the full separation of ferromolybdenum from slag, it is necessary to reduce the melting point and viscosity of slag as much as possible.
During the reaction, silicon is oxidized to silicon dioxide, which forms acidic silicon slag with high viscosity with silicon dioxide in molybdenum baking sand; and the basic slag such as ferrous oxide and alumina produced by the reaction can neutralize and dilute silicon slag; but this is not enough. Fluorite, lime and limestone are usually added to the charge, which can dilute the slag and reduce the melting point of the slag.
However, it should be noted that additives can reduce the melting point and viscosity of slag, but they also consume a lot of heat when they are melted.
Therefore, the amount of additives should be appropriate, to avoid excessive heat loss.