Refractory Technology
Bottom of basic open hearth furnace are constructed of

Dead burnt magnesite ramming mass
Semi-silica bricks
Porous fireclay bricks
Silicon carbide bricks

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Refractory Technology
What is Thoria?

Which is expensive & radioactive, is used in crucibles for melting high purity metals
All of these
Thoria Has high resistance to basic slags
Thoria Has high fusion temperature (> 3000°C) but poor resistance to thermal shock

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Refractory Technology
Magnesite chrome refractories

Have very low thermal co-efficient of expansion
Have better spalling resistance than chrome magnesite refractories
Have very low (50 kg/cm² ) cold crushing strength (C.C.S.), and can not be used in metalcase form
Are not at all resistant to the corrosive action of iron oxide

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