Objective Type Questions on Refractory - Set 07 - ObjectiveBooks

Objective Type Questions on Refractory - Set 07

Practice Test: Question Set - 07

1. Chromite refractories
    (A) Are bonded with lime and clay
    (B) (Free from silica) have better thermal fatigue resistance than silica and magnesite refractories
    (C) Are resistant to basic slag
    (D) All (a), (b) and (c)

2. Addition of grog in fireclay brick during its manufacture is advantageous, because it results in
    (A) Less shrinkage in heating, decreased apparent porosity & increased specific gravity
    (B) High strength & thermal spalling resistance
    (C) Less addition of water to get a workable plasticity & lesser time required for drying the raw refractories and hence increased rate of production
    (D) All (a), (b) and (c)

3. Zircon refractories have
    (A) Low co-efficient of expansion
    (B) High RUL (1600°C) and refractoriness (> 2000°C)
    (C) High spalling resistance
    (D) All (a), (b) and (c)

4. Use of higher percentage of lime for bonding silica bricks, reduces their
    (A) Strength
    (B) Abrasion resistance
    (C) Both (a) & (b)
    (D) Neither (a) nor (b)

5. Cermets are combination of ceramic and metallic materials due to which they have high strength & resistance to high temperature. Cermets are used in the
    (A) Hearth of the blast furnace
    (B) Nuclear reactors, missiles & space crafts
    (C) Insulation of high temperature furnaces
    (D) Roof of electric furnaces

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

7. 'Super refractories' are made from pure
    (A) Carbides
    (B) Oxides
    (C) Borides
    (D) Nitrides

8. Which is the stable form of silica upto 1470°C?
    (A) Quartz
    (B) Cristobalite
    (C) Tridymite
    (D) None of these

9. Skull is not formed on the carbon blocks in the hearth of a blast furnace, when it becomes cold, because of its
    (A) Non-wetting characteristic
    (B) High thermal conductivity
    (C) High crushing strength
    (D) None of these

10. Thermal spalling mainly occurs during __________ of furnaces.
    (A) Cooling down
    (B) Warming up
    (C) Both (a) & (b)
    (D) Neither (a) nor (b)

11. Maximum safe working temperature for fireclay bricks is about __________ °C.
    (A) 1150
    (B) 1300
    (C) 1450
    (D) 1550

12. High alumina refractories are used in the
    (A) Dome of blast furnace stoves
    (B) Electric arc furnace roof
    (C) Glass melting furnaces
    (D) All (a), (b) and (c)

13. Which is the stable form of silica between 1470°C and the melting point 1713°C?
    (A) Cristobalite
    (B) Tridymite
    (C) Quartz
    (D) None of these

14. ________ is not a single oxide-refractory.
    (A) Zirconia
    (B) Silicon carbide
    (C) Magnesia
    (D) None of these

15. Cold crushing strength of a refractory does not depend upon its
    (A) Shape
    (B) Composition
    (C) Firing temperature
    (D) Texture

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