Q.1

Cermets are combination of ceramic and metallic materials due to which they have high strength & resistance to high temperature. Cermets are used in the

  • hearth of the blast furnace.
  • nuclear reactors, missiles & space crafts.
  • insulation of high temperature furnaces.
  • roof of electric furnaces.
Q.2

Firing temperature of magnesite bricks is about __________ °C.

  • 800-1000
  • 1000-1200
  • 1600-1800
  • 2400-2600
Q.3

Maximum alumina content in high alumina refractory can be as high as __________ percent.

  • 30
  • 50
  • 70
  • 90
Q.4

Magnesite refractories are used for the construction of those furnaces, which are

  • not required to resist the corrosive action of basic slag.
  • not subjected to fluctuation in temperature.
  • used for raising & maintaining high temperature.
  • both (b) and (c)
Q.5

Which is not a basic refractory ?

  • Chrome magnesite
  • Magnesite
  • Dolomite
  • Silicon carbide
Q.6

Thoria

  • has high fusion temperature (> 3000°C) but poor resistance to thermal shock.
  • has high resistance to basic slags.
  • which is expensive & radioactive, is used in crucibles for melting high purity metals.
  • all (a), (b) and (c).
Q.7

Hot metal runner in blast furnace are lined with __________ bricks.

  • silica
  • carborundum
  • fireclay
  • magnesite
Q.8

Hollow refractory bricks are made by

  • slip casting
  • hand moulding
  • pressing/machine moulding
  • extrusion
Q.9

Roof of a basic electric furnace is made of __________ bricks.

  • superduty fireclay
  • silica
  • chromite
  • none of these
Q.10

Which property of refractories is the most important for top section of the blast furnace?

  • Resistance to abrasion.
  • Resistance to slag peneration.
  • Stability of volume at high temperature.
  • Resistance to corrosion by slag.
Q.11

Spray test determines the __________ of refractories.

  • resistance to slag penetration
  • resistance to CO attack
  • RUL
  • permanent linear change
Q.12

Quartz is

  • stable form of silica upto 870°C.
  • converted to tridymite on firing between 870 to 1470°C.
  • transformed to crystoballite on heating above 1470°C.
  • all (a), (b) and (c).
Q.13

An indication of degree of firing in silica brick is its

  • specific gravity
  • fusion point
  • RUL
  • none of these
Q.14

High density refractory bricks have lower

  • spalling resistance.
  • thermal conductivity.
  • fusion point.
  • slag penetration resistance.
Q.15

Cold crushing strength of refractories depends upon its

  • composition
  • texture
  • firing temperature
  • all (a), (b) and (c)
Q.16

Periclase is

  • crystalline form of MgO.
  • MgCO3.
  • ZrSO4.
  • amorphous magnesite.
Q.17

Maximum water percentage in refractory mix meant for hand moulding may be as high as __________ percent.

  • 2-3
  • 5-7
  • 7-12
  • 14-20
Q.18

Si percentage in silica refractories used in the walls of coke oven is about

  • 45
  • 60
  • 80
  • 95
Q.19

Bottom of basic open hearth furnace are constructed of

  • dead burnt magnesite ramming mass.
  • porous fireclay bricks.
  • semi-silica bricks.
  • silicon carbide bricks.
Q.20

Silliminite (Al2O3.SiO2) refractory, which is a neutral refractory, is not used in

  • pottery furnace
  • glass melting furnace
  • crucibles
  • gas retorts
Q.21

Tar bonded dolomite bricks

  • are stored under controlled temperature & humidity to avoid hydration.
  • are used in outer lining of L.D. converters.
  • have poorer hydration resistance than pitch bonded bricks.
  • all (a), (b) and (c)
Q.22

Which of the following is not a neutral refractory ?

  • Silicon carbide
  • Magnesite
  • Chromite
  • Graphite
Q.23

Fireclay bricks are never used in the

  • beehive oven
  • coke oven walls
  • zinc roaster
  • lead blast furnace
Q.24

Silica bricks are attacked by basic slags at high temperature. Which of the following is not used solely as a binding material?

  • aluminium phosphate
  • water
  • lime
  • plaster of paris
Q.25

Which form of silica has the highest specific gravity ?

  • Quartz
  • Cristobalite
  • Tridymite
  • All have the same specific gravity
Q.26

Refractories used in/for __________ should have low thermal conductivity.

  • coke ovens
  • insulation
  • regenerators
  • muffle furnaces
Q.27

Most Cermets, which normally have high thermal conductivity and high thermal shock resistance, comprises of ceramic & metallic components of __________ percent respectively.

  • 80 and 20
  • 20 and 80
  • 50 and 50
  • 60 and 40
Q.28

Which is not a high alumina refractory ?

  • Mullite
  • Corrundum
  • Bauxite
  • Dolomite
Q.29

Zircon refractories have

  • low co-efficient of expansion.
  • high RUL (1600°C) and refractoriness (> 2000°C).
  • high spalling resistance.
  • all (a), (b) and (c).
Q.30

Cermets are

  • composite material containing both ceramic & metallic constituents.
  • having high strength & resistance to high temperature.
  • used in space vehicles, missiles & nuclear energy plants.
  • all (a), (b) and (c).
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