High alumina bricks in the XZK-SK series are the standard workhorse refractories of the alumina-silica family, with Al2O3 contents of 55%, 65%, 70% and 82% and refractoriness expressed on the Orton cone scale as SK36, SK37, SK38 and SK40. They are the brick to specify for structural and backing...
High alumina bricks in the XZK-SK series are the standard workhorse refractories of the alumina-silica family, with Al2O3 contents of 55%, 65%, 70% and 82% and refractoriness expressed on the Orton cone scale as SK36, SK37, SK38 and SK40. They are the brick to specify for structural and backing positions where the duty is high temperature and moderate chemistry rather than direct glass contact.
XZK Group presses the SK series on the same CNC presses and fires it in the same tunnel kilns as the rest of our alumina-silica range, so the four grades are delivered to the same dimensional and density tolerances as our premium sintered products.
High alumina bricks sit between fireclay and the mullite-corundum materials. As Al2O3 rises from 55% to 82%, the mineralogy shifts from a clay-bonded mullite body towards a mullite-rich, corundum-bearing structure, and refractoriness under load rises with it from 1450°C at SK36 to 1550°C at SK40. Bulk density climbs from the 2.25–2.40 g/cm3 band to 2.50–2.70 g/cm3, and cold crushing strength from 45 MPa to 70 MPa.
The SK number is the pyrometric cone equivalent, obtained by comparing the deformation of a test cone against a standard Orton cone. It is a direct measure of refractoriness, and it is the traditional way the glass and steel industries name these bricks, which is why XZK keeps the SK designation alongside the chemical grade.
Manufacture is conventional high-alumina practice: bauxite and clay raw materials, graded aggregate, automatic batching, high-pressure pressing and firing to a controlled curve. Because these bricks are produced in volume for many positions, consistency between batches matters as much as peak performance, and density is set by press force rather than by operator judgement.
| Technical Properties | XZK-SK36 | XZK-SK37 | XZK-SK38 | XZK-SK40 |
| Al₂O₃ (%) | ≥ 55 | ≥ 65 | ≥ 70 | ≥ 82 |
| Fe₂O₃ (%) | ≤ 2.0 | ≤ 2.0 | ≤ 2.0 | ≤ 2.0 |
| Refractoriness (SK) | 36 | 37 | 38 | 40 |
| Refractoriness Under Load (0.2MPa, ℃) | ≥ 1450 | ≥ 1480 | ≥ 1530 | ≥ 1550 |
| Bulk Density (g/cm³) | 2.25 - 2.40 | 2.30 - 2.50 | 2.40 - 2.60 | 2.50 - 2.70 |
| Cold Crushing Strength (MPa) | ≥ 45 | ≥ 50 | ≥ 60 | ≥ 70 |
Test methods follow GB/T and ISO practice; ASTM equivalents and full certificates of analysis are issued with every shipment.
Choosing between the four SK grades is a matter of matching alumina content to the position. The rule is to use the lowest grade that satisfies the temperature and load of the zone, because cost rises steeply with alumina content while the benefit beyond the requirement is small.
SK36 (55% Al2O3, SK36, RUL 1450°C) is the lightest grade, used for backing and flue work. SK37 (65%) and SK38 (70%) step up refractoriness and strength and cover the bulk of regenerator walls and superstructure backing. SK40 (82%, RUL 1550°C, cold crushing strength 70 MPa) is the densest and strongest of the series and is used where the backing brick approaches the working lining.
All four grades are made in the same plant and can be supplied as one zoned package, which keeps joints, tolerances and the delivery schedule consistent across the furnace.
SK series bricks are the general-purpose alumina-silica material of a glass furnace, used wherever high temperature is combined with a moderate chemical load:
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.
SK series bricks are supplied with low porosity fire clay bricks, mullite bricks, phosphate-bonded high alumina bricks and high alumina silicon carbide bricks. See the alumina-silicon bricks range or browse all refractory products.
Acid Resistance, %:＞99.8;
Bulk Density, g/cm3:2.3-2.4;
Water Absorption, %:≤0.5;
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