Refractories pdf Online Practice Test - Set 08 - ObjectiveBooks

Refractories pdf Online Practice Test - Set 08

Practice Test: Question Set - 08

1. Chrome magnesite brick is not used for lining the
    (A) Hearth of soaking pits
    (B) Bottom hearth of reheating furnace
    (C) Coke oven regenerator
    (D) Burning zone of limestone rotary kilns

2. Thoria
    (A) Has high fusion temperature (> 3000°C) but poor resistance to thermal shock
    (B) Has high resistance to basic slags
    (C) Which is expensive & radioactive, is used in crucibles for melting high purity metals
    (D) All (a), (b) and (c)

3. Most Cermets, which normally have high thermal conductivity and high thermal shock resistance, comprises of ceramic & metallic components of __________ percent respectively.
    (A) 80 and 20
    (B) 20 and 80
    (C) 50 and 50
    (D) 60 and 40

4. Chromite refractories are
    (A) Acidic refractory
    (B) Neutral refractory
    (C) Basic refractory
    (D) Fired at a temperature of 600°C only

5. ________ of carbon blocks in the hearth of blast furnace helps in avoiding skull formation, when it becomes cold.
    (A) High thermal conductivity
    (B) Low porosity
    (C) Non-wetting characteristics
    (D) High density

6. Vacuum steel degassing units are lined with
    (A) Silica bricks
    (B) Low duty firebricks
    (C) High alumina bricks
    (D) Graphite blocks

7. Rotary kilns meant for calcination of limestone are lined with chrome magnesite in _________ zone.
    (A) Preheating
    (B) Cooling
    (C) Burning
    (D) All the above

8. With increasing alumina content, the fusion point of high alumina refractories
    (A) Increases
    (B) Decreases
    (C) Remain constant
    (D) May increase or decrease; depends on its alumina content

9. Semi-silica bricks compared to silica bricks have
    (A) Less fusion point
    (B) Better spalling resistance
    (C) Both (a) and (b)
    (D) Neither (a) not (b)

10. Walls, roofs & combustion chambers of annealing furnaces are made of ________ bricks.
    (A) High duty fireclay
    (B) Silica
    (C) Mullite
    (D) Carborundum

11. Which of the following impurities reduces the refractoriness of magnesite bricks?
    (A) Al2O3
    (B) CaO
    (C) SiO2
    (D) All (a), (b) & (c)

12. Cold crushing strength of ordinary fireclay brick is about 950 kg/cm2. On exposure to a temperature of about 1500°C, its crushing strength may come down to as low as _________ kg/cm2.
    (A) 450
    (B) 250
    (C) 150
    (D) 65

13. SiO2 percentage in firebrick is about
    (A) 35-40
    (B) 55-60
    (C) 80-85
    (D) > 94

14. Thoria is an expensive refractory material and is radioactive in nature. Thorium oxide is used in the manufacture of
    (A) Segar cones
    (B) Muffles for muffle furnaces
    (C) Insulating bricks
    (D) Crucibles used for melting of high purity metals

15. Pick out the wrong statement.
    (A) A ceramic material which becomes fluid upon heating and can be moulded in liquid/viscous state is termed s glass
    (B) Ceramic materials do not undergo vitrification on heating
    (C) Ceramic materials are brittle in nature
    (D) Non-oxide ceramic materials generally act as a semi-conductor

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