- Time:Jul 25, 2023
First. Reasons for the formation of pores in refractory materials
Porosity in refractory materials refers to the small holes or voids that exist inside the material. These pores are usually caused by several reasons:
1. Raw material characteristics: The raw materials of some refractory materials may contain gas or volatile substances. When these gases or volatile substances are released during heating, pores form. For example, some clay-based raw materials contain moisture, and when heated, the moisture evaporates to produce steam, which causes pores to form.
2. Hardening shrinkage: Some refractory materials will experience hardening shrinkage during the heating process, that is, volume reduction. Voids form when the surface and interior of a material are constrained from shrinking freely. This usually occurs during pouring or coating processes where the material cannot fully shrink due to external constraints before curing.
3. Release of volatile substances: Some additives or adhesives may decompose or burn at high temperature, producing gas. These gases can become trapped inside the material, forming pores. For example, organic fibers or organic binders may decompose and burn in high temperature environments, releasing gases.
4. Reaction to generate gas: Certain chemical reactions will generate gas, leading to the formation of pores. For example, during the sintering process of some refractory materials, gas phase reactions may occur to generate gases. These gases often cannot escape completely, forming pores.
5. Bubble diffusion: At high temperature, the gas in the bubble or void will expand due to the thermal expansion effect. If these air bubbles cannot be effectively removed or the material is not fully densified, pores will form.
Second. Measures to reduce the formation of pores in refractory materials
1. Control the quality of raw materials and select raw materials with low volatility and low gas content.
2. Optimize the formula and use suitable additives and adhesives to reduce gas release and chemical reactions.
3. Control the heating and cooling speed to avoid uneven shrinkage caused by rapid temperature change and thermal stress.
4. Adopt proper pouring, compaction and vibration process to ensure the compactness of the material.
5. Strictly control the atmosphere during sintering or curing to avoid oxidation reaction and gas generation.
In summary, the formation of pores in refractory materials is mainly affected by factors such as raw material properties, thermal stress, additives, and chemical reactions. Through reasonable material selection and construction control, the generation of pores can be minimized and the quality and performance of refractory materials can be improved.
