Ferrosilicon is mainly used as a deoxidizer and alloy additive in steelmaking, and also used in casting, mineral processing, welding rod, light metal industry and as a reducing agent for smelting certain metals.
Ferrosilicon varieties include 90% silicon-containing ferrosilicon, 75% silicon-containing ferrosilicon, 65% silicon-containing ferrosilicon, and 45% silicon-containing ferrosilicon according to the silicon content. Some countries mainly produce ferrosilicon containing 75% silicon, and some countries mainly produce ferrosilicon containing 45% silicon and ferrosilicon containing 65% silicon. The main raw material for smelting ferrosilicon is silica ore (quartz, silica). The SiO2 in the ore is generally required to be higher than 96%. When smelting high-silicon ferrosilicon, it is higher than 98%. The P2O5 in the ore should not exceed 0.02%. , Al2O3 should not exceed 1.5%.
Low-silicon ferrosilicon (containing 10%~15% silicon) can be smelted with iron ore and ore in a blast furnace, which requires a higher coke ratio and blast temperature. During operation, the furnace top temperature is high, the gas contains a lot of dust, and the production operation is difficult. In the 1970s, almost all of them were converted to electric furnace production. High-silicon ferrosilicon is smelted in a reduction electric furnace with carbonaceous lining, using silica, steel shavings, and coke as raw materials.
Electric furnace ferrosilicon is smelted without slag. The raw materials must be clean and must not be mixed with mud, sand and other impurities. Adding wood chips and coal to the charge can improve the performance of the charge. During the smelting process, the surface of the material is easy to crust and “sting fire” (the surface of the material sprays fire), so it must be “punched” frequently. The furnace produces ferrosilicon every 2 to 4 hours, and casts it into an ingot with a thickness of less than 100 mm in the ingot mold. Refining ferrosilicon mostly adopts semi-closed electric furnace with low fume hood, which is convenient for heat recovery and smoke and dust removal; for the production of high silicon ferrosilicon (containing more than 75% silicon), most of them use rotary electric furnace to reduce furnace pounding. The capacity of large-scale ferrosilicon electric furnace is 10000~96000 kVA, and the power consumption of ferrosilicon production is about: 45% ferrosilicon, 5000 kWh/ton; 75% ferrosilicon, 9000 kWh/ton; 90% ferrosilicon, 14000 kw hour/ton. In order to meet the requirement that the aluminum content of ferrosilicon should not be too high for electrical steel, it can be refined by oxygen blowing or chlorine blowing.
During the storage and transportation of ferrosilicon, it is easy to pulverize under certain conditions. This is because the volume expansion is caused by the phase transformation of FeSi and FeSi2 containing about 34% silicon and 50%~60% silicon. Phosphorus, sulfur, calcium, aluminum in impurities, and humid atmosphere will promote ferrosilicon pulverization, and ferrosilicon ingots are easily pulverized due to segregation during slow cooling. Gases such as hydrogen, phosphine and arsine released during ferrosilicon pulverization can cause explosions, and the latter two gases are poisonous, so the storage and transportation of ferrosilicon must be well ventilated to prevent moisture.