Generally, the C/S of melting furnace slag is ≈ 0.3-1.0, but in order to improve the melting efficiency, reduce the melting point, solidify (slag) heavy metals and harmful substances, the composition of the melt is usually adjusted (usually by adding CaO and SiO2), which results in a change in alkalinity and requires corresponding adjustments to the adaptability of the refractory materials.
It can be seen that the selection basis of refractory materials for melting furnaces cannot only consider corrosion resistance. There are also cases where the service life of refractory materials is significantly shortened due to changes in operating conditions, changes in slag composition, and fluctuations in melting temperature, but there is no universal material suitable for this condition. Therefore, the corresponding refractory materials should be selected based on the main factors that cause the damage of refractory materials. It has now been confirmed that the damage of refractory materials in the lining of melting furnaces is mainly controlled by slag composition and operating conditions (temperature, atmosphere, etc.). Therefore, the main criteria for selecting refractory materials for melting furnaces are:
(1) When the slag basicity is not less than 1.0 or the Fe2O3 content is high, basic (MgO) and carbon refractory materials are selected; when the slag basicity C/S is less than 1.0, Al2O3, Cr2O3 and SiC refractory materials are selected.
(2) Depending on the operating conditions (temperature, atmosphere, etc.), the following factors need to be considered when selecting refractory materials for melting furnaces;
1) Since the erosion of refractory materials will increase sharply when the temperature exceeds 1450~1500℃, it is necessary to comprehensively consider the use location, cooling conditions and furnace structure;
2) The erosion loss of refractory materials is not only caused by the slag composition, but also easily caused by the atmosphere in the furnace and the flow of slag;
3) C and SiC refractory materials with good corrosion resistance and corrosion resistance are prone to oxidation loss.