Magnesia bricks, typically containing MgO ≥85%, are essential refractory materials engineered specifically for high-temperature furnaces operating between 1600℃ and 1800℃. Their outstanding alkaline slag resistance, mechanical strength, and thermal stability make them indispensable in the steel industry and cement industry, where equipment continually faces severe thermal, chemical, and mechanical stress.
This guide provides a comprehensive explanation of the core benefits of magnesia bricks, their targeted applications in steelmaking and cement production, detailed performance metrics, and practical selection guidelines for industrial buyers. Whether used in blast furnaces, converters, rotary kilns, or preheaters, magnesia bricks offer reliable protection and long-term performance for high-temperature industrial furnaces.
Magnesia bricks are specifically formulated to solve a series of critical challenges in high-temperature furnace environments. Their chemical composition, structural density, and thermal properties enable them to withstand extreme industrial stresses—making them one of the most reliable refractory solutions for modern metallurgical and cement processes.
Magnesia bricks offer exceptional heat endurance, featuring:
Long-term service temperature: 1600℃–1700℃
Short-term peak temperature: up to 1800℃
These properties ensure that the brick lining remains stable in the burning zone of cement kilns, the slag line of steel converters, and the bosh and hearth areas of blast furnaces. Even under continuous exposure to molten slag, oxygen-rich flames, and rapid heat fluctuations, magnesia bricks maintain structural integrity without softening, warping, or collapsing.
With MgO contents typically above 85–98%, magnesia bricks can withstand extreme alkaline environments. In both steelmaking and cement clinker production, alkaline slag corrosion is the leading cause of refractory wear. Magnesia’s chemical stability significantly improves lining longevity:
Service life extended by 50–80% compared to ordinary refractory bricks
Ideal for zones with alkaline steel slag, cement clinker dust, and alkali vapors
This resistance to alkali attack is a primary reason why magnesia brick for high-temperature furnaces remains the dominant choice in severe environments.
Magnesia bricks endure heavy physical stress caused by:
ore charging impact,
abrasive clinker movement,
rotational friction in rotary kilns,
high-velocity gas flows.
Key mechanical properties include:
Cold compressive strength ≥70 MPa
Wear resistance index ≤0.2 g/cm²
Units lined with magnesia bricks exhibit reduced surface erosion and more stable operational cycles.
Low thermal shrinkage ensures that the furnace lining maintains its original geometry even at elevated temperatures. Meanwhile, high thermal shock resistance ensures that magnesia bricks survive rapid temperature changes during furnace start-ups, shutdowns, and process fluctuations.
Performance metrics:
Thermal shrinkage at 1600℃ ≤0.5%
Thermal shock cycles ≥30 (1100℃→20℃)
This combination prevents brick cracking, spalling, and deformation—common failure modes in high-temperature furnace linings.
With dense microstructures and appropriate thermal conductivity levels, magnesia bricks improve furnace energy efficiency by:
Reducing heat loss through the lining
Enhancing furnace thermal insulation
Stabilizing surface temperature outside the furnace shell
Long-term efficiency gains of 10–15% are achievable in well-designed steel and cement furnaces using high-grade magnesia bricks.
Magnesia bricks are not universally used across all furnace zones—they are strategically placed in areas where extreme heat, alkaline slag, and mechanical loading are the most severe. Below is a detailed breakdown of how the steel industry and cement industry apply magnesia brick linings.
In the steelmaking industry, magnesia bricks are indispensable due to their alkaline resistance and ability to withstand molten iron and slag conditions. They are widely used in:
Key parts: hearth sidewalls, bosh, belly, slag line
Recommended type: high-purity magnesia bricks (MgO ≥90%)
Why suitable: stable performance under 1500℃–1600℃, strong corrosion resistance against iron and basic slag, excellent durability under charging impact.
Key parts: slag line, impact area, tapping zone
Recommended type: magnesia-alumina spinel bricks (MgO 80–85% + Al₂O₃ 10–15%)
Why suitable: superior thermal shock resistance during oxygen blowing, strong anti-erosion performance.
Key parts: slag line, working lining
Recommended type: dolomite-magnesia bricks (MgO 75–80% + CaO 10–15%)
Why suitable: good compatibility with molten steel, high resistance to basic slag, minimal steel contamination.
Industry value:
Magnesia brick linings extend furnace life by 30–40% and reduce downtime, increasing steelmaking efficiency and lowering maintenance costs.
Cement production involves aggressive alkaline dust, high-heat zones, and continuous abrasion. Magnesia bricks play a vital role in:
Key parts: burning zone, transition zone
Recommended types:
High-purity magnesia bricks (MgO ≥90%)
Magnesia-chrome bricks (MgO 85% + Cr₂O₃ 8–10%)
Why suitable: withstand 1450–1600℃, strong alkali corrosion resistance, good fracture toughness.
Recommended type: magnesia-alumina bricks (MgO 60–70% + Al₂O₃ 25–30%)
Why suitable: strong thermal shock resistance to survive frequent temperature cycles.
Recommended type: lightweight magnesia insulating bricks (density ≤1.5 g/cm³)
Why suitable: provide insulation and reduce energy loss during clinker cooling.
Industry value:
Magnesia linings extend rotary kiln service life by 2–3 years and improve plant energy efficiency through better heat retention.
To ensure reliability in high-temperature furnaces, magnesia bricks undergo strict performance testing. Below is a table summarizing key metrics.
| Performance Indicator | Specification Range | Unit | Testing Standard |
|---|---|---|---|
| MgO Content | 85–98% | – | ISO 8008 |
| Long-Term Service Temperature | 1600–1700℃ | ℃ | ASTM C171 |
| Short-Term Peak Temperature | 1750–1800℃ | ℃ | ASTM C171 |
| Cold Compressive Strength | ≥70 MPa | MPa | ISO 10059 |
| Apparent Porosity | ≤16% | % | ISO 5017 |
| Thermal Shrinkage at 1600℃ | ≤0.5% | – | ASTM C325 |
| Wear Resistance Index | ≤0.2 g/cm² | g/cm² | GB/T 18301 |
| Alkaline Slag Resistance | Excellent | – | DIN 51069 |
Selecting the right magnesia brick grade ensures optimal longevity and furnace stability.
Temperature:
≥1600℃ → high-purity magnesia bricks (MgO ≥90%)
1400–1600℃ → magnesia-alumina spinel bricks
Corrosion Conditions:
Severe alkaline slag → MgO ≥85%
Steel slag → MgO ≥90%
Mechanical Load:
High-impact zones (EAF, bosh) → compressive strength ≥80 MPa
Industry-Specific Needs:
Steel converters: spinel bricks
Cement burning zone: high-MgO bricks
Preheaters: magnesia-alumina bricks
Store bricks in a dry environment to prevent moisture absorption.
Use MgO-based mortar for installation.
Leave appropriate thermal expansion joints.
Increase furnace temperature gradually during start-up.
Magnesia bricks are the optimal refractory solution for high-temperature furnaces used in the steel industry and cement industry. Their exceptional temperature stability, alkaline slag resistance, thermal shock performance, and mechanical strength make them ideal for harsh zones such as blast furnace bosh areas, steel converters, and cement kiln burning zones.
Key benefits include:
1600℃–1800℃ temperature resistance
High resistance to alkaline slag
Superior strength & low shrinkage
Improved energy efficiency
Extended furnace service life
Magnesia brick selection should always be based on temperature, chemical environment, mechanical stress, and furnace design requirements.
The main raw materials of magnesia carbon bricks include fused magnesia or sintered magnesia, flake graphite, organic bonds and antioxidants.
High melting point basic oxide magnesium oxide (melting point 2800℃)
Checker bricks are heat transfer media used in the regenerative chambers of blast furnaces and hot blast stoves.
