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MCQs

Total Questions : 868 | Page 10 of 87 pages
Question 91. Porosity of fireclay refractories is __________ percent.
  1.    5-10
  2.    10-25
  3.    25-35
  4.    35-50
 Discuss Question
Answer: Option B. -> 10-25
Question 92. Cold crushing strength of a refractory does not depend upon its
  1.    Shape
  2.    Composition
  3.    Firing temperature
  4.    Texture
 Discuss Question
Answer: Option A. -> Shape
Question 93. Vacuum steel degassing units are lined with
  1.    Silica bricks
  2.    Low duty firebricks
  3.    High alumina bricks
  4.    Graphite blocks
 Discuss Question
Answer: Option C. -> High alumina bricks
Question 94. 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
 Discuss Question
Answer: Option A. -> Spalling resistance
Question 95. Which property is important for bricks used in the combustion chamber & dome of blast furnace stoves?
  1.    High refractoriness
  2.    High resistance to spalling
  3.    High strength and density
  4.    All of the above
 Discuss Question
Answer: Option A. -> High refractoriness
Question 96. Thermal conductivity of refractory bricks
  1.    Increases with decrease in porosity
  2.    Decreases with decreases in porosity
  3.    Is independent of its porosity and is maximum for insulating bricks
  4.    Increases with the amount of air entrapped in pores
 Discuss Question
Answer: Option A. -> Increases with decrease in porosity
Question 97. Thermal spalling mainly occurs during __________ of furnaces.
  1.    Cooling down
  2.    Warming up
  3.    Both A & B
  4.    Neither A nor B
 Discuss Question
Answer: Option C. -> Both A & B
Question 98. Refractoriness under loads (RUL) is quite close to the fusion temperature (PCE) for __________ bricks.
  1.    Fireclay
  2.    Silica
  3.    Dolomite
  4.    Very low alumina
 Discuss Question
Answer: Option B. -> Silica
Question 99. Which is the stable form of silica upto 1470°C ?
  1.    Quartz
  2.    Cristobalite
  3.    Tridymite
  4.    None of these
 Discuss Question
Answer: Option C. -> Tridymite
Question 100. Which is the stable form of silica below 870°C ?
  1.    Tridymite
  2.    Cristobalite
  3.    Quartz
  4.    None of these
 Discuss Question
Answer: Option C. -> Quartz

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