Because the electric furnace cover works under high temperature erosion and rapid cooling and heating, the usage conditions are quite harsh. High-alumina bricks are prone to spalling due to electrical holes, while steel fiber-reinforced castables have excellent thermal shock resistance, high-temperature melt erosion resistance, and good high-temperature volume stability, making them stronger in high-temperature structure.
Adding a certain proportion of heat-resistant steel fiber to the castable can improve the stress resistance of the refractory castable and improve the toughness of the castable. Moreover, the steel fiber castable has good thermal shock stability, resistance to cracking and peeling. Reasonable maintenance after construction can better extend the service life of the furnace cover. Therefore, it is best to use steel fiber castables for electric furnace covers.
When producing steel fiber castables, pay attention to using new cement to prepare them with good fluidity, because the compressive strength and flexural strength of castables prepared with old cement will decrease after drying. The fluidity and setting speed are not as good as new cement. Therefore, when preparing and producing castables, newly produced cement must be used as a binding agent to enhance the strength and tensile capacity of steel fiber castables.
How to improve the quality of refractory castables used in electric furnace covers?
In the selection of materials, refractories castables are used in the triangle area of the electric furnace cover. The electric furnace cover mainly uses prefabricated blocks of refractory castables made of corundum, chrome corundum, high alumina, mullite and other materials. Refractory prefabricated blocks have good integrity and corrosion resistance, are easy to construct and have relatively guaranteed construction quality, which greatly improves the overall quality of the electric furnace cover.
Generally, corundum (chrome corundum) prefabricated parts are used in the triangular area of ultra-high-power electric furnace covers. High-aluminum and mullite prefabricated blocks are widely used in the cover triangle of high-power electric furnaces.
Technological measures to improve the quality of refractory castables
1. Aggregates play the role of skeleton and support, while the matrix plays the role of filling pores, wrapping aggregates, and connecting aggregates. Therefore, raw materials with high purity, low impurities, and high-temperature volume stability are the primary conditions.
2. In order to obtain good high temperature performance, the CaO content should be controlled as much as possible, that is, the amount of cement should be reduced as much as possible. As the CaO content increases, the amount of liquid phase increases significantly as the temperature increases.
3. Add an appropriate amount of tAIzOs to increase the medium temperature intensity. The volume shrinkage caused by the crystalline transformation at the medium temperature stage improves the medium temperature strength.
4. Add an appropriate amount of soft clay as a sintering agent to promote liquid phase generation and sintering in order to form a ceramic bond.
5. Improve the refractory castables volume shrinkage of the material during the sintering process and incorporate additives (kyanite, sillimanite, etc.) that produce expansion effects at high temperatures.
6. Add heat-resistant stainless steel fibers to improve thermal stability and toughness.
7. Add an appropriate amount of anti-knock agent to facilitate the smooth discharge of water vapor and improve the baking quality.
