The role of alumina powder cannot be ignored. Its particle morphology, size, particle size distribution and specific surface area will have a great impact on the performance of corundum castables. In particular, the particle size distribution plays an important role in filling the pores between aggregates and increasing the packing density. . The study found that the use of composite micropowders with different particle size distributions can significantly increase the packing density, reduce water consumption, and is beneficial to mechanical properties such as high-temperature flexural resistance and post-thermal shock strength.
The effect of alumina micropowder particle size on the properties of corundum refractory castables was studied, and it was found that as the micropowder particle size decreased, the fluidity and setting time of corundum castables showed an increasing trend. The following is an experimental analysis conducted to analyze the effect of alumina powder content on the high-temperature properties of corundum castables.
The high-temperature elastic modulus test results of castable samples added with different micropowders after heat treatment at 1600°C are shown in the figure. At the same temperature, the elastic modulus of the sample increases with the increase in the amount of micro powder added. At room temperature, when the amount of micro powder added increases from 10% to 22%, the corundum fine powder content decreases from 18% to 6%. When the temperature rises to 1400°C, the elastic modulus of the sample increases from 86.63GPa to 121.65GPa with the increase of micropowder, with an increase of 40.4%. , consistent with the change trend of room temperature flexural strength in Figure 1.
In addition, as the temperature increases, the elastic modulus of the four groups of samples changes in the same trend. It decreases slowly between 30 and 1200°C, but decreases sharply between 1200 and 1500°C. The reason for this is the generation of CA6 in the samples. Both will increase the apparent porosity of the castable at high temperatures, thereby reducing its high-temperature elastic modulus.
It can be seen from the figure that after three water-cooling thermal shocks, the residual flexural strength of the samples is around 5MPa, with little change. Combined with the normal temperature flexural strength in Figure 1, it can be seen that the more alumina powder is added, the lower the flexural strength after thermal shock. The greater the decrease in sample strength, the greater the residual flexural strength retention rate of the sample decreases with the increase in the amount of alumina powder added, and its value decreases from 18.45% to 11.97%, indicating that the thermal shock stability performance of the sample increases with It weakens with the increase of micron powder content. It can be seen that adding too much alumina powder is not conducive to the thermal shock stability of the castable. The reason is that the denser the material, the fewer pores, and the ability to absorb thermal stress generated during thermal shock is weakened, resulting in the thermal shock of the sample with high powder content. The vibration stability is poor.
Through experimental analysis, it can be concluded that with the increase in the content of alumina fine powder and the decrease in the content of corundum fine powder, the normal temperature performance and high temperature performance of the castable samples after heat treatment at different temperatures are improved to varying degrees. After treatment at 1 600 ℃ The flexural strength at room temperature, elastic modulus at room temperature and elastic modulus at 1 400 ℃ of the final sample can be increased by 53.9%, 47.9% and 40.4% respectively.