Magnesium iron spinel bricks are magnesia refractories bonded by magnesioferrite, a spinel that forms a more flexible bond between periclase grains than the brittle direct bond of a pure magnesia brick. The result is a brick with better thermal shock resistance and a strong tendency to hold a...
Magnesium iron spinel bricks are magnesia refractories bonded by magnesioferrite, a spinel that forms a more flexible bond between periclase grains than the brittle direct bond of a pure magnesia brick. The result is a brick with better thermal shock resistance and a strong tendency to hold a kiln coating, which is why it is a standard material for the burning and transition zones of a cement rotary kiln.
XZK Group supplies magnesium iron spinel bricks with magnesia as the main component and iron oxide at typically 5–12%. They are a basic-environment material, used where a coating is part of the lining design.
The brick is made from magnesia with iron oxide either added directly or introduced as a pre-formed magnesioferrite spinel, then fired so the spinel bonds the periclase grains. Compared with a pure magnesia brick, the bond is more compliant: the spinel accommodates some of the strain that would otherwise crack a rigid direct bond, so the brick tolerates thermal cycling better even though its refractoriness is slightly lower.
The second benefit is coating adhesion. In a cement rotary kiln a stable clinker coating protects the brick in the burning zone, and the iron-rich spinel bond holds that coating in place. The iron oxide in the brick is also compatible with the iron-bearing clinker chemistry, so the lining does not react away at the coating interface. Together, the flexible bond and the coating form a lining system that outlasts a brick chosen on refractoriness alone.
The iron content is also the limit. Iron oxide is undesirable in glass contact and in strongly reducing service, where it can be reduced and the bond weakened, so this grade belongs to cement and other basic kilns rather than to a glass melting basin. In a glass regenerator the chrome-free alkali-resistant choice is a magnesia alumina spinel brick, not an iron spinel.
| Project | Magnesium - Iron Spinel Bricks | |||
| MFA - 1 | MFA - 2 | MFA - 3 | ||
| Chemical Composition | MgO% ≥ | 88 | 86 | 85 |
| Fe₂O₃% | 3.0 - 6.0 | 6.0 - 10.0 | 4.0 - 8.0 | |
| Al₂O₃% | 2.0 - 5.0 | 2.0 - 5.0 | 2.0 - 5.0 | |
| SiO₂% ≤ | 1 | 1 | 1 | |
| Bulk Density (g/cm³) | 2.95 | 2.95 | 2.95 | |
| Apparent Porosity % ≤ | 16 | 16 | 16 | |
| Compressive Strength at Normal Temperature MPa ≥ | 80 | 80 | 80 | |
| Initial Softening Temperature under Load °C [0.2MPa×0.6%] ≥ | 1700 | 1650 | 1680 | |
| Thermal-shock Stability, times [1100 °C, water-cooled] ≥ | 10 | 8 | 10 | |
Grades differ mainly by iron content and by whether the spinel is pre-formed or formed in situ during firing. A pre-formed spinel gives a more uniform bond and more predictable thermal shock behaviour; an in-situ bond is economical for general kiln work. Higher iron content improves coating adhesion and thermal shock resistance but lowers refractoriness, so the grade is matched to the coating practice of the particular kiln.
The grade should be chosen against the actual kiln regime rather than by a single specification figure. Where the kiln runs with a stable coating, a higher-iron grade performs well; where cycling is severe and coating is intermittent, the balance shifts. The chromia-bearing alternative is a magnesia chrome brick, the chrome-free alkali-resistant alternative is a magnesia alumina spinel brick, and for steel service a magnesia carbon brick is used.
Magnesium iron spinel bricks are used in basic kilns where thermal cycling and coating control lining life:
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.
Magnesium iron spinel bricks belong to the magnesia refractory range with magnesia bricks, magnesia alumina spinel bricks, magnesia chrome bricks and magnesia carbon bricks. Browse all refractory products.
MgO:87-97.5%;
Bulk Density:2.85-3.20g/cm³;
Cold Crushing Strength:≥50MPa;
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