Refractory Technology Objective Questions & Answers - ObjectiveBooks

Refractory Technology Objective Questions & Answers

Practice Test: Question Set - 15

1. Hot metal runner in blast furnace are lined with __________ bricks.
    (A) Silica
    (B) Carborundum
    (C) Fireclay
    (D) Magnesite

2. Which is an acidic refractory?
    (A) Magnesite
    (B) Dolomite
    (C) Fireclay
    (D) Chrome magnesite

3. Fireclay bricks are not used in the
    (A) Beehive coke oven
    (B) By-product coke oven walls
    (C) Combustion chamber of B.F. stoves
    (D) Coke oven regenerators

4. Which is a neutral refractory?
    (A) Graphite
    (B) Magnesite chrome
    (C) Silica
    (D) Magnesia

5. High porosity refractory bricks have
    (A) Poor resistance to the penetration of molten slag, metal & flue gases
    (B) Poor heat conductivity & low strength
    (C) Better thermal spalling resistance
    (D) All (a), (b) and (c)

6. Which is not an acidic refractory?
    (A) Silica
    (B) Fireclay
    (C) High alumina refractory
    (D) Carbon black

7. Fireclay bricks are used in the
    (A) Coke ovens regenerator
    (B) Outer lining of L.D. converter
    (C) Hearth bottom of blast furnace
    (D) Coke oven walls

8. Magnesite refractories are generally not used in the
    (A) Electric furnace walls
    (B) Steel melting furnace
    (C) Open hearth furnace
    (D) Burning zone of cement kilns

9. Fusion point of a basic refractory material is
    (A) Reduced by the addition of acid oxides
    (B) Increased by the addition of acid oxides
    (C) Not affected by the addition of acid oxides
    (D) Always less than 1000°C

10. Thermal conductivity of refractory bricks
    (A) Increases with decrease in porosity
    (B) Decreases with decreases in porosity
    (C) Is independent of its porosity and is maximum for insulating bricks
    (D) Increases with the amount of air entrapped in pores

11. Thermal diffusivity of a refractory brick is high, when its __________ is high.
    (A) Density
    (B) Specific heat
    (C) Thermal conductivity
    (D) None of these

12. Which form of silica has the highest specific gravity?
    (A) Quartz
    (B) Cristobalite
    (C) Tridymite
    (D) All have the same specific gravity

13. With increase in the alumina content, the refractoriness of high alumina refractories
    (A) Increases
    (B) Decreases
    (C) Remain same
    (D) May increase or decrease

14. Pick out the wrong statement.
    (A) Refractories used in muffle furnace should have low thermal conductivity
    (B) The electrical resistivity of refractories drops rapidly with rise in temperature
    (C) For reducing spalling tendency, the refractory should be well fired and its porosity should be more
    (D) Refractoriness under load (RUL) of a refractory is always less than its refractoriness

15. Test piece for determination of RUL of a refractory is heated in a/an
    (A) Oxidizing atmosphere
    (B) Reducing atmosphere
    (C) Electric furnace
    (D) Neutral atmosphere

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