The chrome-zirconia-mullite brick is the patented Three-Resistant (3R) refractory: one brick engineered to resist spalling, erosion and thermal shock together, the three mechanisms that normally force a compromise in the combustion zone of a glass furnace. The body holds chromia, zirconia and a...
The chrome-zirconia-mullite brick is the patented Three-Resistant (3R) refractory: one brick engineered to resist spalling, erosion and thermal shock together, the three mechanisms that normally force a compromise in the combustion zone of a glass furnace. The body holds chromia, zirconia and a mullite-corundum matrix in a single dense structure.
XZK's XZK-3R is protected by Chinese invention patent ZL201310431067.6. It is used at burner blocks, port necks, crown corners and regenerator hot zones, where chrome corundum alone would be limited by thermal shock and mullite alone by corrosion.
The three-resistant name states a mechanism, not a marketing claim. Corrosion resistance comes from chromia, which forms a solid solution in the corundum lattice, raises the refractoriness under load to at least 1700°C and suppresses wetting by glass melt, alkali and slag so that the corrosion reaction at the hot face is slowed at its source. Spalling resistance comes from the zirconia fraction: its phase transformation absorbs strain energy and arrests the microcracks that would otherwise link up and release a spall from the brick face. Thermal shock resistance comes from the mullite matrix, which accommodates rapid temperature change without the brittle fracture a monolithic corundum body would show. Each phase covers the weakness of the other two.
The composition is at least 70% Al2O3, at least 10% Cr2O3 and at least 7% ZrO2, with iron oxide held to 0.3%. Powder blending, pressing on CNC presses and a controlled high-temperature firing schedule bring the three phases into a dense body of 3.3 g/cm3 or more, with apparent porosity at 17% or below and cold crushing strength above 100 MPa. The balance between the phases is the difficult part of the process, because too much chromia costs thermal shock performance while too much zirconia costs strength.
The patent covers the composition and the manufacturing route that keeps those three phases in balance so that one resistance does not cost the others. In service the benefit appears at reversal. A burner block in a reversing furnace holds a flame face at the highest local temperature in the furnace and then meets cold combustion air, every 20 to 30 minutes, for the whole campaign. The 1100°C water-quench test gives at least 10 cycles for the 3R body while its refractoriness under load stays above 1700°C — a combination that neither a straight chrome corundum brick nor a mullite brick reaches on its own.
| Technical Properties | XZK-3R |
| Al₂O₃ (%) | ≥ 70 |
| Cr₂O₃ (%) | ≥ 10 |
| ZrO₂ (%) | ≥ 7 |
| Fe₂O₃ (%) | ≤ 0.3 |
| Bulk Density (g/cm³) | ≥ 3.3 |
| Apparent Porosity (%) | ≤ 17 |
| Cold Crushing Strength (MPa) | ≥ 100 |
| Refractoriness Under Load (0.2MPa, ℃) | ≥ 1700 |
| Thermal Shock Resistance (1100℃ water-cooled, cycles) | ≥ 10 |
Test methods follow GB/T and ISO practice; ASTM equivalents and full certificates of analysis are issued with every shipment.
XZK-3R is supplied as a single grade, because the value of the patented body lies in the fixed balance between chromia, zirconia and the mullite-corundum matrix rather than in a ladder of compositions. Changing the ratio for a cost-reduced variant would remove the property that justifies the material.
Selection is therefore positional: send the furnace zoning drawing and the operating data for the position, and specify 3R where spalling, erosion and thermal shock act together. Where only corrosion resistance is required, chrome corundum bricks are the direct and more economical choice; where the duty is structural and thermal rather than chemical, corundum mullite bricks serve the same position.
The Three-Resistant brick is positioned where the mechanisms it addresses overlap: the combustion and vapour-loaded parts of the furnace, where a single-mechanism material would be at its limit.
Manufacturing is controlled from raw material through to finished brick. Four automatic batching lines feed 20 CNC presses ranging from 630 to 2000 tonnes, so density is set by press force rather than operator judgement, and firing runs through four 108-metre fully automatic tunnel kilns and five ultra-high-temperature shuttle kilns for a uniform soak.
Every batch is tested for bulk density, apparent porosity, cold crushing strength and refractoriness under load, and ships with a certificate of analysis. XZK Group holds ISO 9001, ISO 14001, ISO 45001 and ISO 50001 certification and operates the Henan Provincial Engineering Technology Research Center for Sintered Refractories for Glass Furnaces.
The Three-Resistant brick is used in the combustion system with chrome corundum bricks, corundum mullite bricks, zircon mullite bricks and cylindrical chrome corundum bricks, and with high alumina silicon carbide bricks in high-erosion positions. See the regenerator refractory range or browse all refractory products.
Al₂O₃:≥62%;
Cr₂O₃:≥10%;
Cold Crushing Strength:≥100MPa;
Al₂O₃:≥80%;
Bulk Density:≥2.75g/cm³;
Cold Crushing Strength:≥85MPa;
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