Refractory Technology

21. Bottom of basic open hearth furnace are constructed of

1. Dead burnt magnesite ramming mass
2. Porous fireclay bricks
3. Semi-silica bricks
4. Silicon carbide bricks

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22. Capacity of a refractory brick to withstand-sudden changes in temperature is denoted by the property called

1. Spalling resistance
2. Refractoriness
3. Refractoriness under load (RUL)
4. None of these

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23. Carbon bricks are not used in the lining of the

1. Combustion chamber of blast furnace stoves
2. Electric furnaces
3. Highly chemical resistant equipments
4. Blast furnace hearth

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24. Carbon refractories

1. Do not burn/oxidise, when exposed to air on heating
2. Are not attacked by slags, as they are not wetted by melts
3. Do not resist temperature fluctuations
4. Have extremely low thermal & electrical conductivities

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25. Carbon refractories are exclusively used in the

1. Hearth of blast furnace
2. Walls of coke oven
3. Regenerators of coke oven
4. Side wall of soaking pits

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26. Carbon refractories have very high

1. Wetting characteristics
2. Refractoriness
3. Thermal conductivity
4. Both (B) and (C)

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27. Carbon refractory blocks

1. Are wetted by molten iron
2. Are used in the hearth of blast furnace
3. Are acidic in nature
4. All (A), (B) and (C)

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28. Carborundum used for making crucibles for melting non-ferrous metals is chemically

1. Silicon carbide
2. Silicon nitride
3. Crystalline magnesia
4. Zirconium sulphate

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29. Ceramic recuperators used for waste heat recovery from high temperature flue gas going out of the furnace is made of

1. Fireclay
2. Silicon carbide
3. Corundum
4. Siliceous fireclay

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30. Cermets are

1. Composite material containing both ceramic & metallic constituents
2. Having high strength & resistance to high temperature
3. Used in space vehicles, missiles & nuclear energy plants
4. All (A), (B) and (C)

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