Innovative production technology of ferrosilicon of silicon content of minimum 75% and ultra-law carbon content max. 0.02%

Low-carbon FeSi is applied in refining processes of high-grade steels, special-purpose steels, as well as in comprehensive modifiers and casting mortars obtaining processes, also in processes of pure metals production thanks to silicothermic method of oxides reduction in ores or concretion, that is polymetallic sea sediments. Carbon is particularly unwanted in alloy steels due to carbides generation causing unfavourable changes of microstructure, thus reduction of strength, plasticity and chemical properties, especially corrosion resistance due to depletion of alloying element in the circumcarbide zones. Therefore, reducing carbon content in FeSi, usually added to steel bath, directly translates into quality of smelted steel. For this reason, low-carbon-content FeSi is particularly searched for in metal market. The project objective was obtained thanks to an innovative technology of ferrosilicon refining allowing for removal of carbon from the alloy, at the same time avoiding losses of other elements. It is possible by using adsorbing properties of amorphous silica fume resulting from its ultradispersion (grain size is not larger than 1µm) and considerable specific surface area (25,000 m2/kg). Silicon carbide in liquid FeSi is being bound by silica fume grains and then it forms carbidised particle passing to slag or being adsorbed by the ladle lining.