White fused alumina (WFA) plays a critical role in steel ladle furnaces (SLF) as a high-performance refractory material, primarily used in linings and functional components to withstand harsh operating conditions. Its core functions revolve around protecting the furnace structure, ensuring steel quality, and extending service life, with specific roles detailed below:
1. Refractory Lining for Critical Furnace Zones
WFA is a key raw material for manufacturing refractory bricks/castables used in steel ladle furnace linings, focusing on high-wear and high-corrosion areas:
- Ladle shell lining: Mixed with other refractory materials (e.g., bauxite, spinel) to produce high-alumina refractory bricks/castables, forming a thermal insulation and anti-erosion barrier between the steel shell and molten steel/slag.
- Slag line zone: The slag line is subjected to severe chemical erosion by molten slag (high in CaO, SiO₂) and mechanical scouring. WFA’s high Al₂O₃ content (≥98%) and dense structure resist slag penetration and dissolution, reducing lining wear.
- Bottom and nozzle areas: Used in refractory components like ladle bottoms and submerged entry nozzles (SEN), leveraging its high mechanical strength to withstand molten steel impact and prevent structural damage.
2. Functional Refractory Components
WFA is processed into specialized functional parts that directly participate in furnace operations:
- Ladle (Ladle porous plugs): WFA is used as the main aggregate for porous plugs, which inject argon into the ladle to stir molten steel. Its high temperature stability and corrosion resistance prevent plug clogging or damage from molten steel/slag, ensuring uniform stirring.
- Refractory castables for repair: WFA-based castables (low-cement or ultra-low-cement) are used for on-site repair of worn linings. They have good fluidity and fast curing properties, enabling quick maintenance to extend the ladle’s service cycle.
3. Enhancing Steel Quality and Furnace Operational Stability
- Minimizing impurity contamination: WFA has ultra-low impurity content (Fe₂O₃, SiO₂ ≤1.5%), so it does not introduce harmful elements (e.g., Fe, Si) into molten steel during service, ensuring the purity of special steels (e.g., alloy steel, stainless steel).
- Resisting thermal shock and structural deformation: Steel ladle furnaces undergo frequent temperature cycles (room temperature to 1600+°C). WFA’s moderate thermal shock resistance and low thermal expansion coefficient prevent lining cracking or spalling, maintaining structural integrity and avoiding molten steel leakage risks.
- Extending service life: Compared to conventional refractory materials (e.g., brown corundum), WFA’s superior corrosion and wear resistance prolongs the service life of ladle linings and components by 20–50%, reducing downtime for lining replacement and lowering production costs.
4. Optimizing Refractory Performance via Composite Formulations
In practical applications, WFA is often compounded with other materials to balance performance:
- Mixed with spinel (MgAl₂O₄) to improve thermal shock resistance, suitable for ladle zones with frequent temperature changes.
- Blended with carbonaceous materials (e.g., graphite) to enhance slag resistance, targeting high-corrosion slag line areas.
- Used as fine powder additive in refractory castables to increase density and reduce porosity, improving the material’s overall anti-erosion capability.
