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Analysis of chemical and physical erosion mechanism for AOD lining refractories(2)

[06/11/2021]



Due to the high carbon and silicon content of molten iron and high-carbon ferrochromium, the heat is relatively surplus. During the smelting process, the temperature in the furnace quickly rises above 1700. Due to the vortex action of the molten steel near the gun hole, the air muzzle chemical reaction The large amount of heat generated directly follows the vortex of the molten steel and acts on the furnace lining near the air gun eye. The temperature in this area is higher than that of any other parts. The carbon in the molten steel will be reduced to the MgO in the furnace lining as the molten steel washes the furnace lining. Mg volatilizes and corrodes the furnace lining. It can be found from the oxygen potential diagram of the oxide in Figure 4. When the temperature is above 1750, the decomposition free energy of CO begins to be lower than that of MgO, so that the chemical reaction MgO+C=Mg+Co can proceed. , The higher the temperature, the greater the erosion of C to the furnace, another important reason why the erosion near the air gun is faster than other places.

(2) Physical erosion, the solubility of magnesium oxide and calcium oxide in steel is extremely low, which can be ignored. In addition to mechanical erosion and weathering, the physical erosion is the longer the furnace is used, the greater the mechanical erosion and weathering will be, so I won’t discuss it here. In addition, there is another important physical erosion phenomenon: furnace lining fracture and delamination. This discussion only discusses and analyzes the cause of furnace lining fracture and delamination.

The magnesia-calcium fire brick refractories are selected, processed, and press-formed by the machine, and then dried and fired into several stages. There are certain pores on the surface and inside of the brick body. During use, the slag liquid and molten steel will flow into the pores. Infiltration, as can be seen from the two bricks with different porosity in Figure 1, the more the porosity, the more obvious the infiltration. When a certain amount of slag or molten steel penetrates into the brick, the brick body will crack due to the inconsistency of the expansion coefficient of the brick, the slag and the molten steel when the temperature changes greatly. Then it falls off by the scouring action of molten steel, slag and furnace gas. From the furnace in the smelting in Figure 2, it can be seen that the bricks from the top of the air gun to the check line and under the air gun are unevenly broken and fallen off.
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