Semi‑Silica Brick
Semi‑Silica Brick are characterized by a dominant SILICA (SiO2) content, with ALUMINA (Al2O3) being the primary secondary component. They are chemically between Fireclay and true Silica refractories.
| CATEGORY | SiO2 CONTENT | Al2O3 CONTENT | PRIMARY ADVANTAGE |
| SEMI-SILICA | 85% to 92% | 6% to 10% | Excellent volume stability & high TUL |
| FIRECLAY (High Duty) | 50% to 60% | 30% to 45% | Cost and versatility |
| TRUE SILICA | 94% to 98% | < 1% | Max TUL and volume stability at high T |
Key Properties and Performance
| PROPERTY | TYPICAL PERFORMANCE | VARIATION WITH SiO2 CONTENT |
| Temperature Under Load TUL | VERY HIGH (Excellent) | IMPROVES with SiO2 content, as the brick structure resists deformation until near the melting point of SiO2. |
| Thermal Shock | POOR TO MODERATE | IMPROVES Al2O content but decreases as the silica transformation phases are traversed upon heating/cooling. |
| Corrosion | EXCELLENT RESISTANCE to ACIDIC slag and fumes | DECREASES rapidly with exposure to basic slag CaO, MgO or high alkali vapor, which lowers the fusion point. |
| Volume Stability | EXCEPTIONAL at high temperatures | CRITICAL: Stable volume at high temperatures, but major volume changes occur during initial heat-up due to SiO2 phase transformations. |
Semi‑Silica Brick
Advantages and Key Characteristics
Semi-Silica bricks are chosen when the high temperature and superior TUL of Silica are needed, but where the slightly lower cost and enhanced structural stability (due to some Al2O3) are desired.
- High Refractoriness Under Load TUL : The dominant silica phase ensures the bricks remain rigid under structural load almost up to the fusion point, preventing creep and deformation in arches and crowns.
- Excellent Acid Resistance: Inherently resistant to acidic melts, slag, and fumes, making it ideal for processes where SiO2-rich ashes or products are involved.
- Volume Stability at High Temperatures: Once the necessary low-temperature SiO2 phase inversions are complete, the brick exhibits negligible volume change during operation, maintaining tight joints in large structures.
Typical Industries and Applications
Semi-Silica is used as a less-demanding alternative to pure Silica in applications requiring structural strength at high heat:
- Glass Industry: Crowns and checker settings in glass melting furnaces.
- Coke Ovens: Walls and roofs of large coke oven batteries.
- Ferrous Industry: Crowns of large hot blast stoves (HBS) and some reheat furnace roofs.
Furnace Areas and Service Zones
Semi-Silica is specifically used where the temperature is high and the load is structural:
- FURNACE CROWNS AND ARCHES: The most common application, leveraging the high TUL to maintain the structural integrity of large, self-supporting roofs.
- HOT ZONES (Non-Contact): Used in areas with high radiant heat but minimal contact with highly corrosive slag.
- COKE OVEN WALLS: Selected for its stability at the high, steady operating temperatures of the coking process.
Key Data Sheet Properties to Consider
The selection criteria hinge on volume stability and temperature limits:
- SiO2 Content: Confirmation that it falls in the 85-92% range.
- Refractoriness Under Load TUL: THE CRITICAL VALUE. Must demonstrate structural stability above the maximum expected crown temperature (often > 1650°C).
- Permanent Linear Change PLC: The brick should show minimal PLC after the initial thermal cycle, indicating that SiO2 conversions are minimized in service.
- Alkali and Fe2O3 Content: Must be low, as these impurities act as fluxes and drastically lower the melting point of the SiO2 bond.
Technical Guidance: Semi-Silica bricks are extremely sensitive to basic fluxes (CaO, MgO) and low temperatures. They must not be exposed to temperatures below 500°C after the initial thermal conversion, as this can lead to catastrophic cracking due to the reverse SiO2 phase inversions. Use only in high-temperature applications with a consistent, controlled firing schedule.
✨ Customization Services
We offer product customization services, allowing you to tailor the appearance, dimensions, or specific markings of items like refractory shapes or bricks. This includes options for incorporating specific geometric requirements to ensure seamless integration into your process systems.
🔬 Sampling for Testing & Validation
Free product samples are available for thorough testing and validation. This allows you to confirm the quality, compatibility, and performance of our materials—such as specific bricks, castables, or raw materials—before committing to a full order.
💡 Expertise in Refractory Solutions
Leverage our deep expertise to receive detailed, application-specific refractory solutions. We move beyond just selling products by providing comprehensive plans that encompass material selection, installation guidance, and performance optimization to maximize the lifespan and efficiency of your high-temperature processes.
Rabatec products are exclusively manufactured in facilities that have achieved rigorous ISO certifications across Quality (ISO 9001), Environmental Management, and Occupational Health & Safety. This commitment ensures every product, from refractory bricks to specialized equipment, meets the highest global benchmarks for performance, sustainability, and workplace safety.
📦 Logistics Excellence: Shipping, Packaging, and Marking
Minimizing Risk: We manage all logistics to minimize handling touchpoints and transit shock. Our carriers are pre-vetted for their experience in transporting heavy, fragile, and sensitive industrial materials.
Traceability: Every shipment includes comprehensive documentation and tracking information, providing end-to-end visibility and ensuring precise delivery coordination for your site.
Protection is Paramount: Our packaging strictly follows industry standards to prevent damage, corner chipping, and moisture absorption—especially critical for materials like Basic Refractory Bricks and Refractory Mortars & Mixes.
Robust Palletization: Products are secured on fumigated, high-strength export pallets (e.g., 1100x950mm or similar sturdy dimensions) using heavy-duty strapping and durable protective wrapping (polyethylene sheeting, cardboard, etc.) to withstand long-distance travel and multiple loadings.
Moisture Control: Sensitive materials are protected with appropriate sealing and, where necessary, desiccants or moisture-vapor proof enclosures to maintain the product's integrity until installation.
Clear Identification: All outer packaging is clearly marked on multiple sides with large, legible text for immediate identification and safe handling.
Full Traceability: Markings include all essential data points: Product Name, Quality Grade, Batch Number, Quantity, Net/Gross Weight, Order Number, and the Final Destination/Construction Area. This ensures every pallet can be accounted for and correctly staged upon arrival.
Safety & Compliance: We adhere to all regulatory requirements for marking, labeling, and placarding—especially for any items classified as Dangerous Goods—to ensure full compliance with international and domestic transport regulations.
❓ Frequently Asked Questions (FAQ)
Question | Elaborated Answer |
Q: What is the Refractoriness Under Load (RUL) of your refractories? | A: Refractoriness Under Load (RUL) is a critical property that defines the maximum temperature our materials can withstand while under compressive stress before deforming (softening). Since we offer a wide range of materials—from Alumina-Silicate Bricks to high-performance Silicon Carbide Bricks—the RUL varies significantly. For specific product data, please refer to the product data sheet or submit a quote request for the material you are interested in. |
Q: Where are the Rabatec refractories and materials produced? | A: Our products are primarily sourced from specialized manufacturing plants in China. Crucially, these facilities have all undergone rigorous audits and achieved comprehensive ISO certifications (Quality, Environment, and Safety), ensuring that production adheres to the highest global standards for consistency and performance. |
Q: What refractory materials does the company offer? | A: We supply a comprehensive portfolio of advanced refractory solutions, including: Shaped Products: Alumina & Silica Bricks, Basic & Specialized Bricks (e.g., Magnesia), SiC & Structural Ceramics, and Precast Shapes. Monolithic Products: Refractory Castables, Mixes & Mortars. Insulation: Insulation Fibre and High-Performance Insulation Products. |
Q: How should I choose the appropriate refractory material for my application? | A: Selecting the correct refractory is paramount to process efficiency. The choice depends on three key factors: 1. Operating Environment: Maximum process temperature and thermal cycling (shock). 2. Chemical Attack: Type of slag, molten metal, or corrosive gas being handled (acidic, neutral, or basic). 3. Mechanical Stress: Abrasion, erosion, and static load requirements. We recommend utilizing our detailed refractory solutions service to consult with our engineers for an optimized, application-specific recommendation. |
Q: Which monolithic material should I choose when patching an existing lining? | A: For patching and minor repairs, the ideal monolithic material depends on the parent lining material, the patching depth, and the need for a rapid return to service. Common choices include: Refractory Mortars & Mixes (for minor joints/surfaces) or Plastic Refractories (for areas requiring physical compaction). Always choose a patch material chemically compatible with the existing lining to ensure proper bonding and service life. |
Q: Can I receive product samples before placing a major order? | A: Yes. We gladly provide product samples for your internal testing and validation purposes. This ensures you can confirm the quality, composition, and fit of the material—such as our Refractory Castables or Alumina-Silicate Bricks—in your specific operational environment before committing to a bulk purchase. |
Q: Do you provide certifications to verify material quality? | A: Absolutely. We provide product-related inspection certificates and quality assurance documentation upon request. This verifies that your order has passed all internal quality control checks and meets the required material specifications and industry standards. |
Q: What measures are taken for product protection during transport? | A: We ensure quick, reliable transport by using robust, industrial packaging that strictly follows industry standards. This includes high-strength palletization, heavy-duty strapping, and weather-resistant wrapping to protect fragile items like bricks and mixes from corner chipping, mechanical damage, and moisture during transit. |
