Ⅰ. Identify the Application Scenario and Operating Requirements
Operating Temperature: The refractoriness of magnesia-chrome bricks must be higher than the operating temperature. Their refractoriness under load is typically 50-100°C higher than the kiln’s maximum operating temperature to prevent softening and deformation at high temperatures.
Medium Corrosion: Analyze the composition of the media in contact with the kiln. For example, the molten glass in a glass melting furnace contains a high amount of Na₂O, which easily reacts with magnesia-chrome bricks. Therefore, magnesia-chrome bricks with a high Cr₂O₃ content and a dense structure should be selected to improve corrosion resistance.
Thermal Shock Stability Requirements: For areas subject to frequent temperature fluctuations (such as the kiln door opening and the transition zone between the cooling zone and the firing zone), magnesia-chrome bricks must exhibit excellent thermal shock stability.
Mechanical Load: Consider the mechanical stresses on the bricks during kiln operation. Select magnesia-chrome bricks with high bulk density and high room-temperature compressive strength to resist mechanical damage.
Ⅱ. Focus on Core Performance Indicators
MgO Content: The higher the MgO content, the greater the alkali resistance (generally, the MgO content is required to be ≥65%, and ≥75% under special conditions).
Cr₂O₃ Content: (Select according to the type of corrosive medium; in acidic environments, the Cr₂O₃ content should be 15%-25%).
Bulk Density: This reflects the density of the brick structure. The higher the density, the greater the resistance to corrosion and wear (≥3.0g/cm³, with ≥3.2g/cm³ required for key areas). )
Apparent Porosity: The lower the porosity, the less permeable the medium and the longer the brick life (≤16%, preferably ≤12%).
Refraction Under Load (0.2 MPa): Determined by the operating temperature, generally ≥1750°C.
Thermal Shock Stability (1100°C water cooling): No cracking or flaking after ≥15 cycles.
Ⅲ.Identifying Product Quality and Supplier Strength
Appearance Inspection: High-quality magnesia-chrome bricks should have a flat, smooth surface, free of defects such as chips, cracks, or dents. The color should be uniform and consistent, with no noticeable color variation.
Qualifications and Test Reports: Suppliers should provide their production license, quality system certification (such as ISO9001), and performance test reports issued by a third-party testing agency.
Production Process and Equipment: Investigate whether the supplier’s production process is advanced.
Industry Reputation and Case Studies: Select a refractory materials supplier with a good reputation and extensive application cases.
IV. Comprehensive Cost-Benefit Analysis
Although the procurement cost of high-quality magnesia-chrome bricks may be higher, their long service life and low failure rate can reduce kiln downtime and maintenance, improving production efficiency and ultimately being more economical in the long run.
In summary: The selection of magnesia-chrome bricks should be based on the application conditions, clearly defining performance requirements and rigorously examining core indicators. At the same time, attention should be paid to product quality identification and supplier assessment. Ultimately, this will achieve a balance between cost and benefit, providing reliable assurance for the safe and stable operation of the kiln.