Refractory Objective Questions and Answers - Set 03 - ObjectiveBooks

Refractory Objective Questions and Answers - Set 03

Practice Test: Question Set - 03

1. Because of its very high refractoriness of the order of __________ °C, silicon carbide refractories are used in zinc smelting furnace, muffle furnace and for supporting the wares in tunnel kilns.
    (A) 1800
    (B) 2200
    (C) 2400
    (D) 2700

2. Cermets are
    (A) Composite material containing both ceramic & metallic constituents
    (B) Having high strength & resistance to high temperature
    (C) Used in space vehicles, missiles & nuclear energy plants
    (D) All (a), (b) and (c)

3. Carbon refractories are exclusively used in the
    (A) Hearth of blast furnace
    (B) Walls of coke oven
    (C) Regenerators of coke oven
    (D) Side wall of soaking pits

4. Dry mix hydraulic compositions of refractory aggregates with suitable bonding materials are called refractory
    (A) Mortars
    (B) Cements
    (C) Castables
    (D) None of these

5. Which is the most stable crystalline form of silica at room temperature?
    (A) Quartz
    (B) Cristobalite
    (C) Tridymite
    (D) None of these

6. Hot face insulating linings of high purity alumina fused mullite are used, where
    (A) Very high temperatures are involved
    (B) Highly reducing conditions are involved
    (C) Presence of iron or silica is harmful
    (D) All (a), (b) and (c)

7. Which of the following bricks has the most close values of RUL and PCE?
    (A) Silica bricks
    (B) Fireclay bricks
    (C) High alumina bricks
    (D) Tar dolomite bricks

8. Periclase refractory contains mainly
    (A) CaO
    (B) MgO
    (C) Al2O3
    (D) SiO2

9. Roof of a basic open hearth furnace is lined with __________ bricks.
    (A) Silica
    (B) Fireclay
    (C) Dolomite
    (D) Magnesite

10. Silica bricks have low spalling resistance below 600°C, due to its
    (A) Very high thermal conductivity
    (B) High co-efficient of expansion upto this temperature
    (C) High thermal diffusivity
    (D) Low refractoriness

11. Chrome magnesite bricks are used in the
    (A) Side walls of soaking pits and arc furnaces
    (B) Copper melting furnaces & converters
    (C) Burner block of glass tanks
    (D) All (a), (b) and (c)

12. Magnesite refractories have low resistance to
    (A) Attack by basic slag
    (B) Abrasion
    (C) Disintegration on sudden change of temperature
    (D) Both (b) and (c)

13. Refractory materials are never used in the construction of
    (A) Segar cones
    (B) Orton cones
    (C) Pressure vessels
    (D) Ovens & retorts

14. Which is a basic refractory?
    (A) Fireclay
    (B) Silica
    (C) Chrome magnesite
    (D) None of these

15. Graphite or carbon refractories
    (A) Exhibit wetting characteristics
    (B) Should be used in neutral or reducing atmosphere
    (C) Exhibit high shrinkage on thermal treatment
    (D) Are not resistant to corrosion by slag

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