Refractory Technology problems
- 1. The highest melting pure oxide (m.p. > 3000°C)is
Options- A. thoria
- B. alumina
- C. beryllia
- D. zirconia Discuss
Correct Answer: thoria
- 2. Natural silica
Options- A. mainly contains quartz.
- B. is not stable at high temperature.
- C. transforms to other allotropic forms i.e tridymite and cristoballite involving very high volume changes.
- D. all (a), (b) and (c). Discuss
Correct Answer: all (a), (b) and (c).
- 3. Bottom of basic open hearth furnace are constructed of
Options- A. dead burnt magnesite ramming mass.
- B. porous fireclay bricks.
- C. semi-silica bricks.
- D. silicon carbide bricks. Discuss
Correct Answer: dead burnt magnesite ramming mass.
- 4. Refractories used in/for __________ should have low thermal conductivity.
Options- A. coke ovens
- B. insulation
- C. regenerators
- D. muffle furnaces Discuss
Correct Answer: insulation
- 5. Magnesite refractories are generally not used in the
Options- A. electric furnace walls.
- B. steel melting furnace.
- C. open hearth furnace.
- D. burning zone of cement kilns. Discuss
Correct Answer: steel melting furnace.
- 6. Carborundum used for making crucibles for melting non-ferrous metals is chemically
Options- A. silicon carbide
- B. silicon nitride
- C. crystalline magnesia
- D. zirconium sulphate Discuss
Correct Answer: silicon carbide
- 7. Refractories subjected to alternate cycles of heating & cooling are liable to loose their resistance to
Options- A. thermal spalling
- B. slag attack
- C. fusion under load
- D. CO attack Discuss
Correct Answer: thermal spalling
- 8. Most Cermets, which normally have high thermal conductivity and high thermal shock resistance, comprises of ceramic & metallic components of __________ percent respectively.
Options- A. 80 and 20
- B. 20 and 80
- C. 50 and 50
- D. 60 and 40 Discuss
Correct Answer: 80 and 20
- 9. Refractory bricks with lower permeability is produced by using
Options- A. higher firing temperature.
- B. higher moulding pressure.
- C. finer grog size.
- D. all (a), (b) and (c). Discuss
Correct Answer: all (a), (b) and (c).
- 10. Which is not a natural insulating material?
Options- A. Diatomaceous earth/kieselgur
- B. Asbestos
- C. Vermiculite
- D. None of these Discuss
Correct Answer: None of these
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