The primary refractory materials for submerged arc furnaces include carbon bricks, magnesia-carbon bricks, silicon carbide bricks, and high-alumina bricks. These are strategically matched to specific zones-furnace bottom, sidewalls, and tap holes-to accommodate diverse smelting conditions for ferrosilicon, silicomanganese, calcium carbide, and other processes.

I. Material Composition and Technical Parameters

1. Carbon Bricks

Composition: Electrically calcined anthracite + graphite + coal tar pitch, available in standard/microporous/ultra-microporous grades.

Performance:Refractoriness: >2000°C, Thermal conductivity: 20–30 W/(m·K), Low porosity (≤1μm), strong resistance to molten iron penetration.

Applications: Furnace bottoms/sidewalls for ferrosilicon, industrial silicon, and calcium carbide furnaces; microporous carbon bricks mandatory for large furnaces (≥75 MVA).

2. Magnesia-Carbon Bricks

Composition: MgO ≥80%+graphite (10–15%), categorized as high-carbon (14–18%) or medium/low-carbon (8–12%).

Performance:Resistant to alkaline slag (CaO-based), thermal shock, and metal penetration.

Applications: Slag zones/sidewalls for ferromanganese, ferrochrome, and calcium carbide furnaces; high-carbon variants suit high-temperature acidic slag (>1700°C, eg, ferrosilicon).

3. Silicon Carbide Bricks (SiC ≥70%, Critical Wear Zones)

Composition: SiC+binders (silicon nitride/clay), commonly silicon nitride-bonded SiC bricks.

Performance:Thermal conductivity: 15–20 W/(m·K), Wear-resistant, resistant to SiO₂/FeO slag, thermal shock≥20 water-cooling cycles.

Applications: Slag zones, tap holes, and iron runners for ferrosilicon furnaces; service life: 6–12 months.

4. High-Alumina Bricks (Transition/Insulation Layers)

Composition: Al₂O₃ 60–80%, available in Grade II/special-grade variants.

Performance: Refractoriness: 1750–1850°C, Thermal insulation, cost-effective.

Applications: Bottom transition layers, sidewall insulation, and non-working layers; thickness: 150–200 mm.

II. Zone-Specific Selection Guidelines

1. Furnace Bottom (Highest Temperature, Severe Erosion)

Structure (Bottom-Up): Asbestos board→fireclay brick (leveling)→high-alumina brick (transition)→microporous carbon brick (working layer, 400–500 mm)→cold-rammed paste (100 mm).

Requirements: Low porosity, high thermal conductivity, penetration resistance; ultra-microporous carbon bricks mandatory for large furnaces.

2. Sidewalls (Slag Zone + Furnace Body)

Slag Zone (Molten Slag Contact): Magnesia-carbon bricks (alkaline slag) or silicon carbide bricks (acidic slag); thickness: 300–400 mm.

Furnace Body (Non-Slag Zone): High-alumina bricks+lightweight insulating bricks (100–150 mm) for thermal insulation.

3. Tap Hole/Slag Tap Hole (Erosion + Thermal Shock)

Primary Material: Silicon nitride-bonded silicon carbide bricks for erosion resistance and thermal shock stability.

Supplementary Solution: Monolithic corundum-SiC castable for seamless construction, minimizing joints.

III. Matching Refractory Materials to Smelting Conditions

V. Key Points for Construction

Carbon Brick Laying: Use a 45° staggered joint pattern.Wide joints (2-3 mm) should be filled with coarse joint paste to prevent iron leakage.

Expansion Joints: Leave an 80-100 mm elastic layer between the furnace wall and shell.Fill this gap with insulating cotton to accommodate thermal expansion.

Furnace Drying: Follow a strict temperature ramp-up curve.Up to 600°C: ≤50°C/hFrom 600°C to 1200°C: ≤30°C/hThis controlled heating prevents cracking.

V. Service Life and Cost Reference

Carbon Brick Lining: 12-24 months (for ferrosilicon furnaces), Large furnaces can last up to 30 months.

Magnesia-Carbon Brick Lining: 6-12 months (for silicomanganese furnaces),The slag line area is prone to erosion and requires regular maintenance.

Silicon Carbide Brick Tapping Port: 6-12 months, significantly longer than traditional high-alumina bricks (1-3 months).

VI. Core Principles for Material Selection

Temperature Compatibility: The refractoriness of the working layer should be at least 200°C higher than the actual furnace temperature (eg, for a 2000°C furnace, select bricks with a refractoriness ≥2200°C).

Slag Resistance Matching: For acidic slags (SiO₂): Select silicon carbide or carbon bricks.For basic slags (CaO): Select magnesia-carbon bricks.

Thermal Shock Stability: In areas with significant temperature fluctuations (tapping ports, slag lines), prioritize silicon carbide or magnesia-carbon bricks due to their superior thermal shock resistance.