Basic Oxygen Furnaces (BOFs) are the workhorses of modern steelmaking, converting hot metal into steel by blowing oxygen to reduce carbon and impurities. These furnaces operate at extreme temperatures of 1,600°C to 1,800°C, exposing their internal structures to intense thermal, chemical, and mechanical stresses. The BOF refractory lining serves as the primary protective barrier, safeguarding the furnace shell while ensuring efficient and continuous operation.
High-quality refractory linings must resist slag erosion, withstand rapid temperature fluctuations, and provide mechanical stability. Materials like magnesia bricks and dolomite bricks for steelmaking are widely used to meet these demanding requirements.
Importance of BOF Refractory Lining
1. Thermal Protection
Without a strong refractory lining, heat loss would be severe, and the furnace structure would quickly deteriorate. The lining acts as a heat shield, sustaining high operational temperatures without deformation.
2. Chemical Resistance
Molten slag in BOFs is highly basic and can be corrosive to most materials. BOF refractory lining ensures chemical compatibility, preventing slag from penetrating and weakening the furnace walls.
3. Mechanical Durability
The furnace undergoes constant tilting, tapping, and charging cycles, placing additional strain on the lining. High-strength refractory materials maintain integrity under these mechanical stresses.
Core Refractory Materials for BOF Linings
Magnesia Bricks
Composition: High-purity magnesium oxide (MgO).
Key Properties:
Superior resistance to basic slag attack.
Excellent refractoriness up to 2,000°C.
Good thermal conductivity and mechanical stability.
Usage Areas:
Primarily used in slag lines, upper barrel zones, and high-wear areas exposed to molten slag and oxygen blowing.
Dolomite Bricks for Steelmaking
Composition: A combination of calcium carbonate and magnesium carbonate, processed through high-temperature firing.
Key Properties:
Good resistance to basic slag erosion.
Cost-effective alternative to pure magnesia bricks.
Suitable hydration resistance after proper treatment.
Usage Areas:
Widely applied in furnace bottoms and lower barrels where cost control and wear resistance are both essential.
BOF Refractory Lining Design
Each zone of a BOF faces different wear conditions, requiring a tailored combination of refractory materials:
Furnace Bottom
Exposed to intense chemical attack from molten metal and slag.
Often lined with dolomite bricks for steelmaking or tar-bonded magnesia-dolomite bricks for better service life.
Barrel & Slag Line
The most severe wear occurs here due to slag turbulence and high oxygen jet velocities.
High-density magnesia bricks or magnesia-carbon bricks are used for maximum corrosion resistance.
Mouth & Cone Section
Faces significant thermal cycling from charging and tapping operations.
Requires shock-resistant materials such as fused magnesia or magnesia-carbon bricks.
Installation Practices for BOF Refractory Lining
Proper installation plays a vital role in maximizing lining performance:
Bricklaying: Skilled bricklaying ensures tight joints and proper alignment to minimize hot spots.
Ramming and Gunning: Used to fill gaps, repair worn areas, and provide additional protection.
Controlled Drying and Preheating: Gradual heating removes residual moisture and prevents thermal shock during initial furnace start-up.
Factors Influencing Lining Performance
Slag Composition
Highly basic slags with varying lime and iron oxide levels demand linings with superior chemical resistance.Operating Temperatures
Exceeding the brick’s service temperature can lead to accelerated wear. Using high-purity magnesia bricks helps maintain thermal stability.Blowing Practices
Oxygen lance positioning and jet velocity significantly affect wear patterns, particularly in the slag line and barrel areas.Maintenance Schedule
Regular gunning repairs and condition monitoring can prolong furnace campaigns and reduce downtime.
Advancements in BOF Refractory Technology
Modern steel plants are adopting advanced materials and monitoring methods to improve furnace performance:
Magnesia-Carbon Bricks: Provide enhanced thermal shock resistance and reduced slag penetration.
Fused Magnesia and Direct-Bonded Bricks: Offer higher density and improved corrosion resistance.
Recycling of Used Bricks: Refractory recycling programs recover magnesia and dolomite aggregates, lowering costs and environmental impact.
Digital Monitoring: Real-time temperature sensors and wear mapping optimize maintenance schedules and minimize lining failures.
Benefits of High-Quality BOF Refractory Lining
Longer Campaign Life – Reduces frequency of relining and unplanned shutdowns.
Improved Steel Quality – Prevents contamination from worn refractory particles.
Lower Operating Costs – Less downtime and reduced material consumption lead to overall savings.
Higher Thermal Efficiency – Retains heat, cutting energy consumption during the refining process.
Conclusion
The BOF refractory lining is one of the most critical elements in steelmaking, directly influencing furnace life, production efficiency, and steel quality. The use of high-grade magnesia bricks and dolomite bricks for steelmaking, combined with advanced installation techniques and proactive maintenance, ensures reliable performance in the harsh conditions of modern steel plants.
At Xintai Refractory, we specialize in delivering high-performance refractory solutions for BOF refractory lining and other critical steelmaking applications. Our team can assess your furnace conditions and recommend the ideal combination of magnesia bricks and dolomite bricks for steelmaking, along with advanced installation techniques, to maximize efficiency and extend furnace life.
Is your BOF lining approaching its service limit? Contact Xintai today for expert consultation and premium refractory products that keep your steelmaking operations running smoothly and cost-effectively.
