Refractory aggregate is the main material in the structure of refractory castables. The dosage is about 70~. Its skeleton function also affects its physical mechanics and high temperature performance. It is especially obvious for castable refractory castables. Therefore, according to the actual situation and technical formulation requirements, a reasonable choice of refractory aggregates, critical particle size and particle size distribution, in order to obtain high-tech ladle refractory castables.
In the case of the same matrix composition, refractory castables were made from different types of refractory aggregates, and the mass ratio of aggregate to matrix material was 7:3. Brown fused alumina has a higher bulk density, a lower water absorption rate, and a smoother and denser granule zoom. Therefore, less water is needed for the same flow when the ingredients are mixed. The volume density of the special bauxite clinker is smaller, the water absorption is centered, and the particles are angular and porous. More, so the amount of water needed for the seasoning is larger; the white corundum has a bulk density, the water absorption rate is high, and the grains are more angular and have a shrinkage hole, so the amount of water required for the seasoning is maximum.
Effect of refractory aggregates on properties of castables. It can be seen from the table that the volumetric density of refractory castables prepared from brown corundum, white corundum, and special yttrium decreases at one time; as the heating temperature increases, the bulk density of the castable decreases, and only the cast of special yttrium and brown fused alumina The bulk density after firing at 1600°C is greater than the bulk density of the drying; the bending strength of the castable increases with it, the increase of white corundum is less, the increase of special enthalpy is more, and the center of brown fused alumina is more With the increase of the sintering temperature, the castables prepared from white corundum aggregates increase in the line expansion after firing, and between 1100 and 1400°C, due to the formation of more minerals such as spinel, the line expands rapidly after firing. Increase. Between 1400°C and 1600°C, the material contains less impurities, so the post-firing line expansion continues to increase steadily. At 1600°C, there is still approximately 2% of line expansion. The castables are made of brown corundum and special aggregates. The change rule is basically similar, and the maximum line expansion after firing at 1400°C. After firing at 1600°C, the content of SiO2 and R2O in the special crucible is the highest, resulting in more liquid phase, which offsets the volume expansion associated with the formation of MA and CA6. Therefore, this type of material exhibits shrinkage after firing and fireproof to the ladle. The use of castables is disadvantageous. This is also the reason for the use of special smashing or ladle refractory castables for ladle, the need to add more magnesian materials; brown fused alumina aggregate castables after 1600 °C change after burning, in between the two, after burning Linear expansion is 0.62%.
One of the characteristics of the high-tech ladle refractory castable is that the critical particle size of the refractory aggregate is expanded from about 10 mm to about 25 mm to improve its thermal shock resistance. Table 3 shows the test results of anti-stripping performance of coarse aggregate castables. Using corundum magnesite spinel refractory castables as standard brick samples, placing them in an electric furnace at 1450°C for a certain period of time, removing the samples and cooling them to room temperature in air, repeating the cycle and measuring the surface cracking conditions. . In the table, △ indicates that the sample is intact and indicates that the sample cracks. The more , the more cracked the sample.
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