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Analysis of chemical and physical erosion mechanism for AOD lining refractories(1)

[06/11/2021]



(1) Chemical attack, including silicon dioxide (SiO2), iron oxide (FeO), and carbon (C).

Since the source molten iron contains a large amount of silicon, it is oxidized to produce acidic oxide silicon dioxide after blowing. When a new furnace is opened for smelting, it takes a certain temperature and time for the lime to melt (melt) into slag. It is difficult for silicon dioxide to be quickly neutralized by lime, and it will follow the molten iron under the agitation of the gas, causing corrosion to the magnesium-calcium material lining, and the reaction produces MgSiO3 and CaSiO3, although MgSiO3 and CaSiO3 are The melting point is above 1550 Celsius and attached to the furnace fire brick to prevent a little corrosion, but the molten iron in the oxidation period contains a lot of FeO, FeO can greatly reduce the melting point of MgSiO3 and CaSiO3, as can be seen in the three series diagram of CaO-SiO2-FeO, Under the action of FeO, the melting point temperature of CaSiO3 can be as low as 1200 Celsius. Because MgO and CaO have very similar chemical and physical properties, MgO and CaO react with silicon dioxide, and the resulting silicate cannot really be attached to the refractory. On the brick, it melts and rises under the action of FeO, and the silicon dioxide continues to react with the furnace lining to corrode the inner lining. From the used magnesium-calcium brick on the left side of Figure 1, the traces of chemical attack can be clearly seen. In addition, near the wind gun eye, due to the vortex action of the molten steel, the chemical reaction heat of the wind gun mouth is quickly applied to the refractory material near the wind gun eye, which has a higher temperature, and the liquid velocity is faster, the flow rate is large, and the contact There is a lot of silica, so the corrosion of the refractory material near the wind gun eye is more obvious. In the furnace in use in Figure 2, it can be seen that the lining near the wind gun eye is obviously sunken.

As the smelting progresses, the temperature of the molten pool rises, and the lime is dissolved (melted) into slag. After the silica is absorbed by the lime, the silicic acid compounds in the molten steel and the slag liquid exist in the form of SiO32- ions, and the chemical equilibrium formula is SiO32- ?SiO2+O2-, therefore, as long as there are SiO32- ions in the molten steel and slag, SiO2 will exist. FeO and SiO2 in the smelting work together to corrode the furnace lining throughout the entire smelting process, increase the alkalinity of the slag, and reduce the smelting time. Controlling the amount of FeO in the slag can slow down the erosion of FeO on the furnace lining.
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