AOD furnace at the beginning of oxygen blowing oxidation decarburization, in the oxidation period, the oxidation of slag and temperature rise to more than 1700; Then into the reduction period, add ferrosilicon or aluminum, reduce the chromium in the slag, in order to improve the alloy yield, at this time the slag alkalinity is still very low; Finally add lime desulphurization, desulphurization needs high alkalinity slag. In the whole smelting process, the furnace slag changes from acidic to alkaline atmosphere from oxidizing atmosphere to reducing atmosphere and then is intermittent operation, the furnace lining temperature is high and the fluctuation is quite large. Therefore, AOD lining service life is very low.
The service life of AOD furnace was only about 30 times before. By improving smelting conditions and adopting measures such as spray repair and maintenance, the service life of AOD furnace generally reached more than 70 times, and many more than 100 times. For AOD furnace, magnesia chrome brick is generally used. Due to the complex production process of magnesia chrome brick, to ultra-high temperature firing, large energy consumption, high cost, especially environmental pollution problems, therefore, magnesia chrome brick was gradually replaced by magnesia calcium brick.
At present, AOD furnace lining kelide kiln refractory development trend is magnesia chrome brick less and less, more and more magnesia calcium brick, some parts with low carbon magnesia calcium material. For magnesium and calcium materials there are asphalt impregnation. It is worth pointing out that when the smelting temperature is very high, the carbon refractory is not suitable due to the internal REDOX reaction. Apply magnesia chrome brick or magnesia calcium brick just go.