As a core material for high-temperature industries, refractory castables‘ wear and thermal shock resistance directly impact equipment lifespan and production safety. To address the issues of castable wear.Thermal cracking in applications such as cement rotary kilns and steel blast furnaces, optimization can be performed from three perspectives: raw materials, processes, and structure. Specific measures are as follows:
1. Raw Material Optimization: Laying a Solid Performance Foundation
Raw material selection is key to improving wear and thermal shock resistance. To improve wear resistance, high-strength aggregates such as silicon carbide and corundum can be incorporated into the castable. These aggregates have a high hardness (Mohs hardness of 8-9) and enhance the material’s erosion resistance. For example, adding 20%-30% silicon carbide to the castable in the transition zone of a cement kiln can reduce wear by over 30%. To improve thermal shock resistance, low-expansion aggregates such as kyanite and sillimanite expand slowly upon heating, offsetting the overall shrinkage stress of the castable. Furthermore, reducing the amount of high-alumina cement,using pure calcium aluminate cement can reduce the risk of internal cracks caused by hydration heat.
2. Process Improvement: Improving Density and Uniformity
The construction process directly impacts the performance of the castable. Control the amount of water added during mixing, strictly adhering to a 6%-8% ratio. Adding too much water will increase porosity and decrease wear resistance. A high-speed mixer can ensure a uniform mix of aggregate and matrix. Vibrating with a high-frequency vibrator of 200-300Hz can eliminate internal bubbles and increase the castable’s bulk density to above 2.8g/cm³. Increased density makes it more difficult for abrasive media to penetrate. Avoid rapidly increasing the temperature during the curing phase. Adopt a “low-temperature curing (20-30°C) → slow drying (50-80°C)” process. This prevents cracking caused by sudden water loss and lays the foundation for thermal shock resistance.
3. Structural Design: Adapting to Working Conditions
Optimizing the structure based on the application scenario can reduce wear and thermal shock damage. For high-wear areas (such as the blast furnace tapping channel), a “gradient structure” design is adopted, with a high-wear-resistant castable (silicon carbide content ≥40%) used for the surface layer, a standard high-aluminum castable for the bottom layer, achieving a balanced performance and cost-effectiveness. For equipment subject to large temperature fluctuations (such as the regenerator of a glass furnace), expansion joints (spaced 1-1.5 meters apart and 2-3 mm wide) are created in the castable and filled with ceramic fiber wool to absorb the expansion stress caused by temperature fluctuations and prevent overall cracking. Furthermore, adding a buffer layer (such as a lightweight insulating castable) between the castable and the metal shell can further mitigate the effects of thermal shock on the material.
In summary, the synergistic effect of raw material selection, process control, and structural optimization can effectively improve the wear resistance and thermal shock resistance of refractory castables, extend their service life under high-temperature and high-wear conditions, and ensure stable industrial production.