Refractory Technology

61. Firing temperature is minimum (1250-1400 °C) for _________ bricks.

1. Fireclay
2. Direct bonded basic
3. Silica
4. Magnesite

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62. Firing temperature of magnesite bricks is about _________ °C.

1. 800-1000
2. 1000-1200
3. 1600-1800
4. 2400-2600

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63. Furnace atmosphere for softening temperature determination of refractories (in which Seger Cones are placed) should be

1. Oxidising
2. Neutral
3. Either (A) or (B)
4. Neither (A) nor (B)

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64. Fusion point of a basic refractory material is

1. Reduced by the addition of acid oxides
2. Increased by the addition of acid oxides
3. Not affected by the addition of acid oxides
4. Always less than 1000°C

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65. Fusion point of an acidic refractory material is

1. Increased by the addition of basic oxides
2. Reduced by the addition of basic oxides
3. Not affected by the addition of basic oxides
4. Always more than 2500°C

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66. Fusion temperature of pure silica (SiO₂) is _________ °C.

1. 1350
2. 1715
3. 2570
4. 2800

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67. Ganister is a source of the

1. Silica
2. Periclase
3. Lime
4. None of these

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68. Graphite or carbon refractories

1. Exhibit wetting characteristics
2. Should be used in neutral or reducing atmosphere
3. Exhibit high shrinkage on thermal treatment
4. Are not resistant to corrosion by slag

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69. Grog

1. Contains both alumina and silica
2. Is crushed firebrick
3. Is a non-plastic material
4. All (A), (B) and (C)

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70. Grog addition in fireclay during brick manufacture is done to

1. Reduce its shrinkage on heating
2. Impart greater spalling resistance
3. Enhance the strength of fired refractories
4. All (A), (B) and (C)

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