Understanding Tundish Burner Block Refractory:

The tundish is a critical intermediate vessel in the continuous casting (CC) process of steelmaking, responsible for stabilizing molten steel flow, regulating temperature, and removing impurities—directly impacting the quality of cast billets and the safety of production operations. The tundish burner block refractory, a core component of the tundish heating system, serves as the "thermal protection core" for the burner, withstanding extreme temperatures (up to 1800℃), thermal shock, and erosion from high-velocity flue gas and molten steel splashes. Selecting, installing, and maintaining high-quality tundish burner block refractory is not only essential for extending the service life of the burner and tundish but also for reducing unplanned shutdowns, lowering maintenance costs, and ensuring stable, efficient steel production.

1. What is Tundish Burner Block Refractory & Its Core Functions?
Before diving into selection and maintenance, it’s critical to understand what a tundish burner block refractory is and why it’s indispensable in continuous casting. The tundish burner is used to preheat the tundish before casting (to prevent thermal shock when molten steel is poured) and to maintain the required temperature during casting (ensuring uniform steel flow and reducing defects like cold shuts). The burner block refractory is a specialized refractory component that surrounds and protects the burner nozzle, forming a sealed, high-temperature-resistant channel for flame and flue gas.

Its core functions are non-negotiable for safe and efficient tundish operation:

- High-Temperature Insulation & Protection: The burner block refractory isolates the high-temperature flame (1600~1800℃) from the tundish shell and surrounding components, preventing overheating, deformation, and oxidation of the steel shell. This is critical because the tundish shell can only withstand temperatures up to 150℃, while the burner’s operating temperature far exceeds this limit. The refractory acts as a thermal barrier, ensuring the shell remains within a safe temperature range ≤150℃.

- Flame Guidance & Stability: It shapes the flame path, ensuring uniform heat distribution inside the tundish and avoiding local overheating (which can damage the tundish lining) or uneven preheating (which leads to molten steel temperature fluctuations). This is especially important for modern蓄热式 burners, which rely on stable flame distribution to maximize heat recovery efficiency.

- Erosion & Wear Resistance: It resists erosion from high-velocity flue gas (containing dust and corrosive substances like K₂O, Na₂O) and splashes of molten steel/slag. Without a durable refractory block, the burner nozzle would quickly wear or crack, leading to flame leakage, uneven heating, and even burner failure.

- Thermal Shock Resistance: The tundish undergoes frequent temperature changes—from room temperature during preheating to 1500℃+ during casting, and back to room temperature after shutdown. The burner block refractory must withstand these rapid thermal cycles without cracking or spalling, which would compromise its protective function and require costly replacements.

- Energy Efficiency Enhancement: High-quality refractory blocks reduce heat loss from the burner, improving the thermal efficiency of the heating system. This aligns with the industry’s focus on energy conservation, as efficient heat utilization can reduce fuel consumption by 5%~10% and lower NOₓ emissions—critical for meeting modern environmental standards.

2. Key Factors to Consider When Selecting Tundish Burner Block Refractory

Selecting the right tundish burner block refractory is not a one-size-fits-all process. It depends on your specific tundish design, burner type (e.g., regenerative burner, direct-fired burner), operating temperature, and steelmaking process. Below are the most critical factors to evaluate—ignoring any of these can lead to premature failure and production disruptions:

2.1 Operating Temperature & Thermal Load

The primary factor is the maximum operating temperature the refractory will withstand. Tundish burners typically operate at 1600~1800℃, with flame temperatures reaching up to 2000℃. The refractory’s refractoriness (maximum temperature it can withstand without melting under no load) must be at least 100~200℃ higher than the maximum operating temperature to ensure long-term stability. For regenerative burners, which operate at higher temperatures and require better heat retention, the refractory should be classified as advanced or特级 (refractoriness ≥1770℃).

Additionally, consider the thermal load—how long the burner operates continuously (e.g., 8~12 hours per casting cycle) and the frequency of temperature cycles (start-up, shutdown). Refractories with high hot compressive strength (≥50MPa at 1400℃) are ideal for high thermal load applications, as they maintain structural integrity under prolonged high temperatures.

2.2 Chemical Erosion Resistance

The tundish environment is harsh, with corrosive media including alkaline slags (CaO, MgO from molten steel), acidic gases (CO₂, SO₂ from fuel combustion), and volatile alkali metals (K₂O, Na₂O). These substances can react with the refractory, causing degradation, spalling, or even melting.

Follow the "acid-base matching principle" for material selection:
     For alkaline environments (common in steelmaking with high CaO content), choose alkaline refractories (e.g., magnesia-alumina spinel) that resist alkaline erosion.For neutral or mixed environments, select neutral refractories (e.g., high-alumina, corundum) that resist both acidic and alkaline erosion.Avoid acidic refractories (e.g., silica bricks) for tundish burner blocks, as they are easily corroded by alkaline slags.

Also, prioritize refractories with low porosity (≤18%)—lower porosity reduces the penetration of corrosive media, extending service life. This is especially important for tundish burner blocks, which are exposed to both high temperatures and corrosive flue gases.

2.3 Thermal Shock Resistance

Thermal shock is the leading cause of tundish burner block failure. The refractory must withstand rapid temperature changes (e.g., from 20℃ to 1600℃ in 1~2 hours during preheating) without cracking. This performance is measured by the number of water-cooling cycles (e.g., 1100℃ water-cooled cycles ≥20 times).

Refractories with high thermal shock resistance typically have a low thermal expansion coefficient (≤5.5×10⁻⁶/℃) and good toughness. For example, corundum-mullite refractories combine high refractoriness with excellent thermal shock stability, making them ideal for tundish burner blocks in high-cycle applications.

2.4 Mechanical Strength & Wear Resistance

The burner block refractory must withstand mechanical stress from installation, tundish vibration, and high-velocity flue gas impact. Key indicators to consider:
     Cold crushing Strength: ≥40MPa (to resist damage during transportation and installation).Hot Compressive Strength: ≥35MPa at 1400℃ (to maintain structural integrity under high temperatures).Wear Resistance: Measured by the abrasion index (≤1.5cm³/1000g). High wear resistance is critical for blocks exposed to high-velocity dust and flue gas.

2.5 Compatibility with Burner Type & Tundish Design

Different burner types require different refractory properties:
     Regenerative Burners: These burners use alternating combustion and exhaust cycles to recover heat, requiring refractories with high heat retention, low thermal conductivity, and excellent thermal shock resistance (e.g., SiMo bricks, corundum-mullite). They also need to withstand higher temperatures (up to 1800℃) and longer operating cycles.Direct-Fired Burners: These operate at lower temperatures (1600~1700℃) and require refractories with good erosion resistance and moderate thermal shock resistance (e.g., high-alumina bricks).

Additionally, the refractory block must fit the tundish’s design—including the burner nozzle size, installation position, and clearance. A poor fit can lead to flame leakage, uneven heating, and premature wear. Work with your refractory supplier to customize the block size and shape for your specific tundish and burner.

2.6 Cost & Long-Term Value

While upfront cost is a consideration, prioritize long-term value over short-term savings. A cheap, low-quality refractory block may need replacement every 1~2 months, leading to frequent shutdowns and higher maintenance costs. For example, a steel plant replaced its low-grade high-alumina burner blocks with corundum-mullite blocks, extending the service life from 2 months to 6 months and reducing maintenance costs by 40%.

Consider the total cost of ownership (TCO)—including the refractory cost, installation cost, downtime cost, and replacement frequency. High-quality refractories may have a higher upfront cost but lower TCO over time, especially as the global耐火材料 market stabilizes and prices begin to rise moderately.

3. Common Types of Tundish Burner Block Refractory & Their Applications

Not all tundish burner block refractories are the same. Each material has distinct properties, making it suitable for specific operating conditions. Below is a detailed breakdown of the most widely used types, their key properties, and applications—covering 95% of steel plant needs:

3.1 High-Alumina Refractory Blocks (Al₂O₃ 60%~80%)

Key Properties: Refractoriness 1750~1850℃, good neutral erosion resistance, moderate thermal shock resistance (1100℃ water-cooled cycles ≥15 times), volume density 2.6~2.8g/cm³, porosity 15%~18%. They are classified as advanced耐火材料, balancing performance and cost.

Applications: Suitable for direct-fired tundish burners with operating temperatures ≤1700℃. Ideal for medium-scale steel plants with moderate production cycles (e.g., 8~10 hours per casting). Widely used in conventional continuous casting lines due to their cost-effectiveness and availability.

Pros: Balanced performance, cost-effective, easy to install, widely available. Cons: Limited thermal shock resistance for high-cycle applications; not suitable for regenerative burners with high temperatures.

3.2 Corundum-Mullite Refractory Blocks (Al₂O₃ 80%~90%)

Key Properties: Refractoriness 1850~1950℃, excellent thermal shock resistance (1100℃ water-cooled cycles ≥25 times), high hot compressive strength (≥50MPa at 1400℃), low thermal expansion coefficient (4.5~5.0×10⁻⁶/℃), good erosion and wear resistance. They are classified as特级耐火材料, offering superior performance.

Applications: Ideal for regenerative tundish burners with operating temperatures up to 1800℃. Suitable for large-scale steel plants with long production cycles (e.g., 12~16 hours per casting) and high thermal loads. Also used in high-quality steel production (e.g., automotive steel, construction steel) where temperature stability is critical.

Pros: Long service life (4~6 months), excellent thermal shock and erosion resistance, energy-efficient. Cons: Higher upfront cost than high-alumina blocks.

3.3 Magnesia-Alumina Spinel Refractory Blocks (MgO 60%~70%, Al₂O₃ 30%~40%)

Key Properties: Refractoriness 1900~2000℃, excellent alkaline erosion resistance, good hot strength, moderate thermal shock resistance (1100℃ water-cooled cycles ≥20 times). They are environmentally friendly alternatives to traditional magnesia-chrome bricks, avoiding hexavalent chromium pollution.

Applications: Suitable for tundish burners in steel plants with high alkaline slag content (e.g., lime-steelmaking processes). Ideal for harsh environments where corrosion is a major concern, such as in advanced continuous casting lines producing high-purity steel.

Pros: Superior alkaline erosion resistance, high refractoriness, environmentally friendly. Cons: Poor resistance to acidic erosion; higher cost than high-alumina blocks.

3.4 Silicon-Molybdenum (SiMo) Refractory Blocks

Key Properties: Refractoriness 1650~1680℃, excellent wear resistance, low thermal conductivity (0.8~1.2W/(m·K)), high thermal shock stability (1100℃ water-cooled cycles ≥30 times), good corrosion resistance. They are optimized for energy efficiency, making them ideal for heat recovery systems.

Applications: Suitable for low-to-medium temperature tundish burners (≤1650℃) and regenerative systems where heat retention and wear resistance are critical. A case study of a 300t/d continuous casting line showed that SiMo burner blocks reduced fuel consumption by 8% and extended service life by 3 months compared to high-alumina blocks.

Pros: Energy-saving, long service life, excellent wear resistance. Cons: Not suitable for high-temperature burners (≥1700℃).