How to improve the quality of refractory castables for electric furnace cover

To improve the quality of refractory castables, the following process measures can be taken:

1) Aggregates serve as a framework and support, while the matrix fills pores, encapsulates aggregates, and acts as a bridge connecting them. Therefore, raw materials with high purity, few impurities, and high-temperature volume stability are paramount.

2) To achieve good high-temperature performance, the CaO content should be minimized, meaning the cement dosage should be minimized. As the CaO content increases, the liquid phase volume increases significantly with increasing temperature.

3) Adding an appropriate amount of Al2O3 improves intermediate-temperature strength. At intermediate temperatures, α-Al2O3 reacts with CaO and CA in the following manner: CaO + Al2O3 → CaO ∠Al2O3, resulting in a volume expansion of 19.6%. CaO ∠Al2O3 + Al2O3 → CaO ∠2Al2O3, resulting in a volume expansion of 12.86%. This expansion compensates for the volume shrinkage of the castable due to dehydration and crystal transformation, improving its medium-temperature strength.

4) Adding an appropriate amount of soft clay as a sintering agent promotes liquid phase formation and sintering, thereby forming a ceramic bond.

5) To mitigate the volume shrinkage of the castable during sintering, additives that expand at high temperatures (such as kyanite and sillimanite) are added.

6) Adding heat-resistant stainless steel fibers improves thermal stability and toughness.

7) Adding an appropriate amount of anti-knock agent facilitates the smooth escape of moisture and improves baking quality.

Long-term practice suggests that while new steelmaking technologies may lead to the partial selection of alkaline materials for electric furnace covers, high-aluminum furnace cover materials made from carefully selected, high-quality raw materials, including new varieties containing "three stones" (corundum, mullite), as well as castables using ultrafine powders and new materials such as chrome corundum, all meet the needs of new technological developments. The addition of steel fiber to steel fiber castables, at approximately 2%, can enhance the strength of the castable.

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