During the smelting and heating process of the charge, the high-valent oxides of manganese and iron in the charge are decomposed by high temperature in the charge zone or reduced to low-oxide by CO. By 1373~1473K, the high-priced manganese oxide is gradually reduced to MnO. All FeO is further reduced to Fe; MnO is relatively stable and can only be directly reduced by carbon. Since SiO 2 is higher in the charge, MnO is combined with it to form a low melting point of manganese silicate. Therefore, the reduction reaction of MnO is actually carried out in the manganese silicate of the liquid slag, and the state and melting point of the manganese silicate are MnO + SiO 2 ===MnSiO 3 t melting = 1250 ° C
2MnO+SiO 2 ===Mn 2 SiO 4 t melt = 1345 ° C
Since manganese and carbon can form a stable compound Mn 3 C, direct reduction with carbon gives a manganese carbide Mn 3 C. Its reaction formula is MnO•SiO 2 +4/3C===1/31/3Mn 3 C+SiO 2 +CO↑
The iron oxide in the charge is easier to reduce than the manganese oxide, and the pre-existing iron forms a co-melt (MnFe) 3 C with manganese, which greatly improves the reduction condition of MnO.
As the temperature increases. Silicon is also reduced, and its reaction formula is SiO 2 +2C===Si+2CO↑
Since the silicon and manganese can produce a more stable compound than MnSi Mn 3 C, when the Si restore them encountered Mn 3 C, Mn 3 C the carbon was displaced, resulting in decrease of carbon content in the alloy, the reaction of formula Is 1/3Mn 3 C+Si===MnSi+1/3C
As the reduced silicon content increases, the manganese carbide is destroyed and the carbon content in the alloy is further reduced.
The total reaction formula for the reduction of manganese-silicon alloy from carbon slag by carbon is
The starting reaction temperature was 773 °C. About 75% of the phosphorus in the charge enters the alloy.
In the smelting process of manganese-silicon alloy, in order to improve the reduction conditions of silicon, there must be enough SiO 2 in the charge to ensure that the smelting process is always under acidic slag; however, if the SiO 2 is excessive in the slag, it will cause the platoon Slag is difficult, usually the slag composition of smelting manganese-silicon alloy is w(SiO 2 )=34%~42%
n(CaO+MgO)/nSiO 2 =0.6~0.8
w(Mn)<8%
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