Magnesia Carbon Bricks | The Forge Fire | Forum

Magnesia Carbon brick is a resin-bonded basic refractory brick made from dead-burned (sintered) or fused magnesia and graphite and bonded with high carbon containing pitch and resin, with some metallic powder as anti-oxidants to protect the carbon. Magnesia Carbon bricks have many advantages over the conventional alumina brick lining.

Between 1975 and 1980 magnesia-carbon refractories were developed and started to be used in Japan first for electric arc furnace hot spots and shortly thereafter for BOFs.

The magnesia carbon brick is produced by adding a carbon-bonding formative agent to dead-burned (sintered) or fused magnesia and graphite, which are then pressed by the usual method and then subjected to heat treatment. It replaces pitch with resin and allows for a dramatic increase in the carbon level as a result of graphite additions. Subsequently, antioxidants are added to the magnesia-carbon brick to protect the carbon from oxidation and improve high temperature strength by the formation of carbides.

Carbon is added to refractories because it is not wetted by slags.The carbon can form a film blocking the slag penetration thereby minimizing the damage it causes to the brick. However, the weakness of carbide is easily oxidized in high temperature environment. In addition, as magnesia-carbon Brick is belong to one of resin-bond bricks, the resistant oxidation is low when they are operated in middle temperature.

The magnesia carbon bricks have high refractoriness as no low melting phase occurs between MgO and C. Because of the non-wetting of carbon, the magnesia carbon bricks prevent the penetration of slag and molten steel. As The magnesia carbon brick is made by high pressure, it shows excellent resistance to thermal shock and slag corrosion at elevated temperatures.

Graphite, the carbon source, has very low thermal expansion and very high thermal conductivity. So magnesia carbon bricks have low thermal expansion and high thermal conductivity, which make magnesia carbon bricks have excellent thermal shock resistance.

It is widely used in converters, BOF, EAF, ladles and refining furnaces as they possess superior slag penetration resistance and excellent thermal shock resistance at elevated temperature because of the non- wetting properties of carbon (graphite) with slag, high thermal conductivity, low thermal expansion and high toughness,etc.