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Effects of the vacuum treatment

[11/10/2021]



Many refining devices have vacuum treatment functions, such as LF-VD, VOD, RH and DH, etc.Vacuum conditions have great effects on the loss of refractory, especially carbon-containing refractory.According to the chemical equilibrium principle, under vacuum conditions, the following reactions are promoted to the right, resulting in the internal gasification of the refractory: MgO + C=Mg + CO, 4MgO + 2Al=3Mg + MgAl2O4,MgO + Si=Mg + SiO, 5MgO + B4C=5Mg + CO + 2B2O2.

The above reactions resulted in the loose interior of the carbon-containing refractory, decreased strength, and even pulverization, making the lining service life linearly decreased with the proportion of VD and treatment time.Therefore, under high temperature vacuum conditions, aluminum powder, it is not appropriate to choose aluminum powder, silicon powder and boron carbide, these additives prone to redox reaction with magnesium oxide.They do not improve the service life of steel bags, but reduce the service life.However, CaO is not easy to redox with carbon, so under certain conditions, MgO-CaO-C is more suitable for magnesium carbon than these special conditions.
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