The steel industry is one of the downstream sectors of refractory materials. Every technological progress in steelmaking depends on the support of refractories.
The development of steelmaking technology based on basic slag systems has promoted the growth of basic refractory materials such as magnesia. However, with further advancements in steelmaking, traditional refractories can no longer fully meet production demands.
As a result, magnesia carbon bricks were developed.
What is Magnesia Carbon Brick?
Traditional magnesia bricks have good high-temperature performance. However, they perform poorly in slag penetration resistance and thermal shock resistance. Therefore, later research focused mainly on improving slag resistance and thermal shock stability.
Carbon has high thermal conductivity and a very low thermal expansion coefficient. It also has poor wettability to molten slag and molten steel. By combining these properties, magnesia-carbon composite refractories effectively overcome the shortcomings of magnesia bricks.
They can significantly extend the service life of furnaces.
Magnesia-carbon bricks are non-burning carbon composite refractories. They are mainly made of high-melting basic magnesium oxide and high-purity graphite. Various non-oxide additives are also added and bonded with carbon-based binders.
magnesia carbon brick properties
Excellent high-temperature resistance
The melting point of MgO is about 2852°C.
This allows the brick to maintain structural stability above 1500°C.
Excellent slag corrosion and penetration resistance
Carbon has low wettability to molten slag and molten steel.
It effectively prevents slag penetration and erosion.
Good thermal shock resistance
Carbon (graphite) has high thermal conductivity and a very low thermal expansion coefficient.
It can efficiently transfer heat and significantly reduces spalling and cracking problems of pure magnesia materials.
Other mechanical and high-temperature properties
- High high-temperature strength and low creep, maintaining good mechanical strength at elevated temperatures.
- Good cold crushing strength and high-temperature modulus of rupture.
Typical values:
cold crushing strength ≥ 25–45 MPa,
hot modulus of rupture at 1400°C ≥ 3–14 MPa (depending on grade). - Bulk density is generally about 2.8–3.1 g/cm³.
Failure Mechanism of Magnesia Carbon Bricks
Carbon oxidation
At high temperatures (especially above 600°C), carbon (graphite) on the brick surface is easily oxidized by oxygen in air or oxides in slag.
This leads to a loose structure, increased porosity, and reduced strength.
That is why antioxidants are added in magnesia-carbon brick formulations to maintain long-term performance.
Slag corrosion
Basic slag or molten steel reacts with MgO to form low-melting compounds.
At the same time, slag can penetrate into the brick, especially after carbon oxidation increases porosity.
This causes chemical dissolution and structural damage.
The slag line area is more severely affected due to long-term contact with the slag-steel interface.
The actual failure of magnesia-carbon bricks is usually not caused by a single factor.
It is the combined result of slag corrosion, carbon oxidation, and other effects.
Main Application Areas of Magnesia Carbon Bricks
Converter slag line
This area is exposed to high temperature and strong erosion from basic slag.
MgO provides strong resistance to basic slag corrosion.
Carbon reduces slag wettability and prevents penetration.
Good thermal shock resistance also reduces spalling, significantly extending furnace life.
Electric arc furnace wall hot spots
This area faces extreme thermal shock, slag corrosion, and frequent temperature fluctuations.
High refractoriness (MgO melting point ~2852°C), combined with carbon’s high thermal conductivity and low expansion, helps reduce thermal stress and spalling.
Ladle slag line
This area is in long-term contact with the steel-slag interface.
It experiences large temperature differences, penetration, and oxidation.
Magnesia-carbon bricks have low wettability to slag and steel, strong anti-penetration ability, and good resistance to corrosion and spalling.
They are especially suitable for continuous casting operations.
Converter lining
These parts endure high-temperature molten bath, mechanical impact, and slag attack.
Magnesia-carbon bricks are suitable due to their combined high-temperature resistance, slag resistance, and thermal shock resistance.
They improve the overall service life of the equipment.
Selection Guide for Magnesia Carbon Bricks
Converter use
Converter slag contains strong oxidizing components.
Therefore, high resistance to slag corrosion is required.
Electro-fused magnesia is usually used as aggregate.
Purity is ≥97%, and carbon content is about 12–16%.
Electric arc furnace wall
This area requires high thermal shock resistance due to high temperature impact and frequent thermal cycling.
Carbon content is slightly higher (12%–18%) to improve thermal conductivity and reduce expansion.
High-purity fused magnesia is preferred, with emphasis on thermal shock resistance.
Ladle slag line
This area requires anti-penetration and anti-oxidation performance.
High-purity fused magnesia (MgO ≥97%) is used with enhanced antioxidants.
Carbon content can be normal or slightly lower.
Conclusion
Magnesia-carbon bricks are an indispensable composite refractory material in steelmaking metallurgy. They will continue to develop in this field in the future. With stricter requirements for clean steel production and low-carbon environmental protection, traditional magnesia-carbon bricks will undergo further optimization.
If your company is looking for high-performance and long-life magnesia-carbon brick solutions, or needs customized selection for converters, ladles, or other working conditions, please feel free to contact us.
We will provide professional differential selection suggestions, product solutions, and on-site technical support based on your furnace type, slag system, and process conditions. We help improve furnace life and reduce refractory consumption.
JHYRef is committed to innovative and green development. We look forward to working with more steel enterprises to explore new low-carbon and high-efficiency refractory application pathways.
