Fluorite is a flux, and its main component is CaF2.
The melting point of pure CaF2 is 1418°C. Fluorite also contains components such as SiO2 and S, so the melting point is around 930°C. After being added to the furnace, the melting point of the high melting point 2CaO·Si02 shell of CaO and lime is reduced, forming a low melting point compound 3CaO. ·CaF2·2SiO2 (melting point is 1362°C) can also form a low melting point compound (1350°C) with MgO, thereby improving the fluidity of the slag. Fluorite has a fast fluxing effect and a short time.
However, excessive use of fluorite will form serious foam slag, causing splashing, while also aggravating the erosion of the furnace lining and polluting the environment.
Therefore, the amount of fluorspar added per ton of steel should be strictly controlled. The fluorspar used in the converter has wCaF2≥85%, wSiO2≤5.0%, wS≤0.10%, wP≤0.06%, the block size is 5~50mm, and it must be dry and clean.
In recent years, due to the insufficient supply of fluorspar, steel mills have tried a variety of fluorspar substitutes from the perspective of environmental protection, all of which are fluxes based on manganese oxide or iron oxide, such as iron-manganese ore, iron oxide scale, and converter soot. , feral bauxite, etc.
Link to this article：The role of fluorite for converters
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