Magnesia carbon bricks combine high-purity magnesia with flake graphite in a carbon bond, giving a refractory that resists basic slag and thermal shock far better than a pure magnesia brick. The graphite raises thermal conductivity and lowers slag wetting, so the brick survives the rapid cycling...
Magnesia carbon bricks combine high-purity magnesia with flake graphite in a carbon bond, giving a refractory that resists basic slag and thermal shock far better than a pure magnesia brick. The graphite raises thermal conductivity and lowers slag wetting, so the brick survives the rapid cycling and heavy slag contact of steelmaking vessels. In the XZK magnesia range they are the steel-side material, distinct from the chrome and spinel grades used in glass and cement kilns.
XZK Group supplies magnesia carbon bricks in carbon levels from about 8% to 20%, with low-carbon grades for clean-steel applications. Their working environment is a basic, slag-bearing one rather than a glass melt.
The brick is made from high-purity sintered or fused magnesia, graded flake graphite of 8–20% by weight, a small addition of antioxidants such as aluminium, silicon or magnesium, and a phenolic resin binder. It is pressed and then heat-treated so the resin cures into a carbon bond. The magnesia supplies refractoriness and basic-slag resistance; the graphite supplies thermal conductivity, low slag wetting and thermal shock resistance; the antioxidants protect the graphite from oxidation.
The carbon bond is what makes the material work. Graphite is not wetted by slag, so molten slag beads on the surface instead of penetrating the brick, and the graphite network conducts heat away from the hot face, which lowers the surface temperature and the thermal gradient across the lining. Antioxidants matter because carbon burns in an oxidising atmosphere: above about 1400°C in air the graphite would be lost, so the additions react preferentially and form a protective layer around the carbon.
The material is not intended for glass melt contact. Carbon is a defect source in glass, causing colour and gas-related faults, and a carbon-bonded brick oxidises in the oxidising atmosphere of a glass furnace. It belongs in steelmaking and other basic, slag-bearing vessels, where its combination of slag resistance and thermal shock tolerance is difficult to match.
| Brand | Apparent Porosity, % ≤ | Bulk Density, g/cm³ | Compressive Strength at Normal Temperature, MPa ≥ | High-temperature Flexural Strength, MPa (1400 °C, 30 min) ≥ | MgO, % ≥ | C, % ≥ |
| MT - 5A | 5 | 3.15 ± 0.08 | 50 | – | 85 | 5 |
| MT - 5B | 6 | 3.10 ± 0.08 | 50 | – | 84 | 5 |
| MT - 5C | 7 | 3.00 ± 0.08 | 45 | – | 82 | 5 |
| MT - 8A | 4.5 | 3.12 ± 0.08 | 45 | – | 82 | 8 |
| MT - 8B | 5 | 3.08 ± 0.08 | 45 | – | 81 | 8 |
| MT - 8C | 6 | 2.98 ± 0.08 | 40 | – | 79 | 8 |
| MT - 10A | 4 | 3.10 ± 0.08 | 40 | 6 | 80 | 10 |
| MT - 10B | 4.5 | 3.05 ± 0.08 | 40 | – | 79 | 10 |
| MT - 10C | 5 | 3.00 ± 0.08 | 35 | – | 77 | 10 |
| MT - 12A | 4 | 3.05 ± 0.08 | 40 | 6 | 78 | 12 |
| MT - 12B | 4 | 3.02 ± 0.08 | 35 | – | 77 | 12 |
| MT - 12C | 4.5 | 3.00 ± 0.08 | 35 | – | 75 | 12 |
| MT - 14A | 3.5 | 3.03 ± 0.08 | 40 | 10 | 76 | 14 |
| MT - 14B | 3.5 | 2.98 ± 0.08 | 35 | – | 74 | 14 |
| MT - 14C | 4 | 2.95 ± 0.08 | 35 | – | 75 | 14 |
| MT - 16A | 3.5 | 3.00 ± 0.08 | 35 | 8 | 74 | 16 |
| MT - 16B | 3.5 | 2.95 ± 0.08 | 35 | – | 72 | 16 |
| MT - 16C | 4 | 2.90 ± 0.08 | 30 | – | 70 | 16 |
| MT - 18A | 3 | 2.97 ± 0.08 | 35 | 10 | 72 | 18 |
| MT - 18B | 3.5 | 2.92 ± 0.08 | 30 | – | 70 | 18 |
| MT - 18C | 4 | 2.87 ± 0.08 | 30 | – | 69 | 18 |
Grades are set mainly by carbon content. A higher-carbon grade of around 14–20% gives the best thermal shock and slag resistance and suits converter and electric arc furnace hot spots. A medium-carbon grade is used for general lining work. A low-carbon grade of about 8% or less is chosen where carbon pickup must be minimised, as in clean-steel ladle practice, and it relies more heavily on magnesia quality and the antioxidant package to keep its performance.
The grade must also be matched to the slag and the thermal load. In basic steelmaking the composition is straightforward; where the environment is more oxidising, the antioxidant addition has to be increased. The other magnesia grades serve different duties: magnesia chrome bricks and magnesia alumina spinel bricks for alkali and sulphate resistance in kilns and regenerators, and pure magnesia bricks for stable high-temperature zones.
Magnesia carbon bricks are specified for basic, slag-bearing steelmaking service:
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.
Magnesia carbon bricks sit within the magnesia refractory range alongside magnesia bricks, magnesia chrome bricks, magnesia alumina spinel bricks and magnesium iron spinel bricks. Browse all refractory products.
MgO:85-88%;
Bulk Density:2.95g/cm³;
Cold Crushing Strength:≥80MPa;
MgO:87-97.5%;
Bulk Density:2.85-3.20g/cm³;
Cold Crushing Strength:≥50MPa;
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