Calcium aluminate flux is used in the refining of liquid steel in both the integrated process (blast furnace and iron ore) and the electric process (electric arc furnace and scrap iron). It is chiefly used in secondary metallurgy in combination with lime, ferro-alloys and sometimes other minerals.
This secondary metallurgy slag is an oxidised liquid which floats on the surface of liquid steel (1,600° C) and acts like a sponge to absorb the impurities consisting mainly of sulphur and non-metallic inclusions. The design of the slag is a critical step impacting the efficiency of the steel refining process.
The most common flux in secondary metallurgy processes is calcium fluoride (CaF2), which facilitates the reaction of reagents in order to obtain a liquid. However, it does not contribute to the slag composition. Another major disadvantage is that CaF2 attacks the refractory lining of the steel ladle. Calcium fluoride also has a harmful effect on the environment during the recycling of the slag because fluorine is leachable, i.e. there is a risk of it being carried by rainwater and polluting ground water.
Calcium aluminate flux meets two major challenges facing steelmakers: it facilitates the formation of slag and helps optimise its composition, in particular the Al2O3/SiO2 ratio. Calcium aluminate flux therefore maximises the efficiency of the steel refining process by:
The LDSF® range: a benchmark solution used for more than 25 years by many steelmakers with all types of metallurgical production tools (LF, VD, VOD, RH, tundish):
LDSF® products are preferably added when the ladle is filled with steel. The early addition enables the rapid formation of a fluid and reactive slag and the efficient dissolution of other slag components. This method maximises the advantages of the MgO when LDSF® products are used by protecting the refractory lining during the first moments of processing, when corrosion is at its highest.