Magnesium oxide has the characteristics of high melting point (>2800°C), strong corrosion resistance to alkaline slag, low oxygenation to molten steel, and good compatibility with molten steel, making magnesium oxide an attractive raw material for refractory materials . In the field of magnesia refractories, magnesia shaped products such as magnesia chrome bricks, magnesia spinel bricks and magnesia carbon bricks are the first to be developed. With the development of refractory materials towards the trend of indeterminate, magnesia castables have been gradually developed.
Refractory castables need to add water during construction. The state of water in materials can be divided into three categories: one is free water condensed on the surface and inside of materials, one is adsorbed water, and the other is structural water in compounds. As the temperature rises, the above three kinds of water are removed in sequence. During the rapid baking and drying stage, the moisture inside the material escapes, resulting in high vapor pressure and thermal stress (caused by temperature gradient). When the force of the two is higher than the ultimate strength of the castable, a burst occurs, which is harmful to production and safety. cause harm. By embedding pressure guide tubes and thermocouples during the preparation of cement-bonded corundum castables, the steam pressure and temperature in the sample were recorded during the heating process. The results showed that the furnace temperature increased at a constant rate, and the internal temperature of the sample also increased linearly. , but the temperature difference between inside and outside is close to 100°C. When the furnace temperature is less than 300°C, the vapor pressure of the sample increases slowly, and in the range of 300°C-400°C, the pressure value increases sharply, and the pressure reaches the maximum at 400°C (the internal temperature of the sample is about 260°C). And the maximum vapor pressure occurs at the center of the sample. Some research results also show that when the cement-free bonded corundum castable containing magnesium oxide and SiO2 micropowder is heated on one side, when the temperature inside the sample reaches 410°C, bursting occurs. The burst point reported above is consistent with the dehydration temperature range of the hydration phase, indicating that the burst temperature of the material is closely related to the dehydration behavior of the hydration phase.
The anti-burst technology actually improves the moisture removal process inside the material and avoids the accumulation of water vapor inside to form a large pressure. Its interior is regarded as a porous medium structure, and the small-sized holes in it have capillary phenomenon, and the existence of additional pressure leads to the formation of liquid level difference inside and outside the tube. The smaller the capillary diameter (radius R), the higher the liquid level rise (h) in the tube, that is, the easier it is to absorb water or water vapor, and the harder it is for water vapor to be eliminated during the heating process.