Refractory Technology

91. Magnesite chrome refractories

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

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92. Magnesite refractories are generally not used in the

1. Electric furnace walls
2. Steel melting furnace
3. Open hearth furnace
4. Burning zone of cement kilns

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93. Magnesite refractories are used for the construction of those furnaces, which are

1. Not required to resist the corrosive action of basic slag
2. Not subjected to fluctuation in temperature
3. Used for raising & maintaining high temperature
4. Both (B) and (C)

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94. Magnesite refractories have low resistance to

1. Attack by basic slag
2. Abrasion
3. Disintegration on sudden change of temperature
4. Both (B) and (C)

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95. Maximum alumina content in high alumina refractory can be as high as _________ percent.

1. 30
2. 50
3. 70
4. 90

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96. Maximum apparent porosity of magnesite bricks is about _________ percent.

1. 8
2. 24
3. 44
4. 58

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97. Maximum safe working temperature for fireclay bricks is about _________ °C.

1. 1150
2. 1300
3. 1450
4. 1550

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98. Maximum shrinkage in volume occurring during burning/firing of dried refractories may be as high as _________ percent.

1. 10
2. 15
3. 20
4. 30

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99. Maximum water percentage in refractory mix meant for hand moulding may be as high as _________ percent.

1. 43892
2. 44017
3. 44172
4. 14-20

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100. Mixing of ground refractory material and water is done in a _________ mill.

1. Pug
2. Ball
3. Tube
4. Rod

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