Sintered Magnesia Refractories

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Sintered Magnesia Refractories

Introduction of Sintered Magnesia Refractories

Magnesite refractories are containing at least 85% magnesium oxide and are one of the most widely used basic refractory bricks. Their main advantage is very high slag resistance to lime and iron-rich slags. It is very important for steelmaking processes. Currently, magnesite refractories are not only used in metallurgical furnaces, they are also used in glass tank checkers, lime, and cement kilns.

Classification and Application of Sintered Magnesite Refractories

Magnesite Refractory Bricks

Magnesite Refractory Bricks are produced from Magnesia raw material and perform excellently at high temperatures. Burned Magnesite Refractory Bricks have the advantage of very strong slag resistance properties. Sintered Magnesite Refractory Bricks are mostly used for: permanent lining of Electric Arc Furnace, steel converters, lime kilns, glass tank regenerators and non-ferrous furnaces.

Magnesite Alumina Spinel Bricks (Mg Al2O4)

Spinel is the magnesium aluminum formulation of the larger spinel group of minerals. The melting point of Magnesia Spinel is 2135 C, and Magnesia Spinel has very high, excellent refractoriness. Magnesia Spinel refractory bricks possess high-melting points, high chemical inertness against both acidic and basic slags, and low expansion values at elevated temperatures and are widely used in zones where there is a big temperature change, cement rotary kilns, vacuum induction furnaces, regenerators of glass tanks, lime kilns, continuous casting tundishes, degasser snorkels, and lances. The main advantages of using Magnesia Spinel bricks are:

  • Very high, excellent refractoriness.
  • Low thermal expansion coefficient.
  • High resistance to thermo-mechanical stress.
  • High resistance to corrosion and changes in the kiln atmosphere.
  • Low content of secondary oxides.
  • Elimination of chromite.
Sintered Magnesia Refractories
Magnesite Alumina Bricks

Magnesite Alumina Bricks

Magnesite Alumina refractory bricks consist of Magnesia and Alumina Bauxite. Magnesite Alumina refractory bricks perform well at high temperatures, and they provide good thermal shock resistance. Magnesite Alumina has the advantages of strong slag resistance and high refractory under-load performance. Magnesite Alumina Refractory Bricks are used in:

  • Steel ladles.
  • The permanent lining of steel furnace.
  • Iron mixer.
  • Many other industrial furnaces.

Magnesite Chrome Bricks (Mg-Cr)

As a result of this reaction, the volume expands by 77.7%, causing serious damage to the magnesia refractories, resulting in cracks or caving. Magnesia bricks must pay attention to moisture-proof during storage.

Magnesite Chrome Refractory Bricks are produced from sintered magnesia and chrome ore by sintering at high temperatures. Magnesite Chrome Refractory Bricks have high bulk density and the advantage of stronger thermal resistance. Magnesite Chrome Refractory Bricks are widely used for:

  • Cement rotary kilns.
  • Glass kiln regenerators.
  • The permanent lining of steel furnaces.
  • The permanent lining of refining ladles.
Magnesite Chrome Bricks (Mg-Cr)
Magnesite Chrome Bricks (Mg-Cr)
Magnesite-Dolomite Refractory Bricks

Magnesite-Dolomite Refractory Bricks

Magnesite Dolomite Refractory Bricks are produced from magnesia that has high purity and density and sintered Magnesia Dolomite grain. Magnesite Dolomite Refractory Bricks have the advantages of good thermal resistance, anti-spalling performance, and good coating protection to the kilns when they are used for cement rotary kilns. Magnesite Dolomite Refractory Bricks are mainly used for:

  • Bottom and lining of basic open-hearth furnaces.
  • Bottom and lining of electric furnaces.
  • Permanent layers of converter furnace.
  • Non-ferrous metal melting furnaces.
  • High-temperature tunnel kilns.
  • Cement rotary kilns.

The Main Properties of Magnesia Refractory Bricks

  • Refractory|
    Because the melting point of magnesite crystals is very high, up to 2800 °C, the refractory degree of magnesia refractory is the highest in general refractory bricks, usually above 2000 °C.
  • High-temperature structural strength
    The high-temperature strength of magnesia refractory is not good, and refractoriness under load is between 1500~1550 °C, which is more than 500 °C lower than the refractory.
  • Slag resistance
    Magnesia refractory is an alkaline refractory material, which has strong resistance to alkaline slags such as CaO and FeO, so it is usually used as a masonry material for alkaline smelting furnaces, but its resistance to acid slag is poor. Magnesia refractories cannot be in contact with acidic refractory materials, and they will react with each other and be corroded when they are above 1500 °C. Therefore, magnesia refractory cannot be mixed with silica bricks.
  • Thermal stability
    The thermal stability of magnesia refractory is very poor, and it can only withstand water cooling 2~8 times, which is its great disadvantage.
  • Volume stability
    The thermal expansion coefficient of magnesia refractory is large, and the linear expansion coefficient between 20~1500 °C is 14.3×106, so sufficient expansion joints should be left during the brick-laying process.
  • Thermal conductivity
    The thermal conductivity of magnesia refractory bricks is about several times that of clay refractory bricks. Therefore, the outer layer of the furnace made of magnesia refractories should generally have a sufficient thermal insulation layer. However, the thermal conductivity of magnesia refractories decreases with increasing temperature.
  • Hydration
    Magnesium oxide that is not calcined enough reacts with water to produce the following reactions: MgO+H2O→Mg(OH)2
    As a result of this reaction, the volume expands by 77.7%, causing serious damage to the magnesia refractories, resulting in cracks or caving. Magnesia bricks must pay attention to moisture-proof during storage.
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