Q.1

Fusion temperature of pure silica (SiO2) is __________ °C.

  • 1350
  • 1715
  • 2570
  • 2800
Q.2

Crushing strength of a refractory

  • increases with rise in service temperature.
  • decreases with rise in service temperature.
  • is unaffected with change in service temperature.
  • decreases with increase in porosity.
Q.3

Ramming masses are used for

  • obtaining monolithic working faces.
  • repairing construction of various furnace parts.
  • both (a) & (b).
  • neither (a) nor (b).
Q.4

Which is the most stable crystalline form of silica at room temperature ?

  • Quartz
  • Cristobalite
  • Tridymite
  • None of these
Q.5

Which of the following consumes the maximum tonnage of refractories annually in an integrated steel plant ?

  • Soaking pits
  • Ceheating furnace
  • L.D. converter
  • Rotary lime kiln
Q.6

Cold crushing strength of ordinary fireclay brick is aboutkg/cm2 . On exposure to a temperature of about 1500°C, its crushing strength may come down to as low as __________ kg/cm2 .

  • 450
  • 250
  • 150
  • 65
Q.7

Except __________ , all other refractories are bad conductors of electricity (i.e, have low electrical conductivity).

  • fireclay
  • carborundum
  • graphite
  • chromite
Q.8

The linear thermal expansion of __________ bricks upto°C is very low of the order of ≤ 0.5 percent.

  • fireclay
  • silica
  • magnesite
  • corundum
Q.9

Silica refractories

  • crack when subjected to sudden change of temperature.
  • can not be used in the dome of hot blast stoves.
  • have lower thermal conductivity than fireclay bricks.
  • all (a), (b) and (c)
Q.10

In panel test for spalling resistance, the average face temperature of panel assembly is maintained at __________ °C forhours.

  • 700
  • 1000
  • 1600
  • 2000
Q.11

Fireclay bricks is not used for lining the

  • cupola.
  • gas producer.
  • bottom of hot metal mixer.
  • roof of open hearth furnace.
Q.12

__________ nozzles are used in continuous casting of steel,

  • Zircon
  • Thoria
  • Carborundum
  • Beryllia
Q.13

Zirconia refractory

  • does not react with basic slags.
  • is produced from baddeleyite.
  • can not be used as an insulator.
  • has poor electrical conductivity at high temperature.
Q.14

Which refractory must have controlled atmosphere (temperature and humidity) for its safe storage ?

  • Tar bonded dolomite bricks
  • Fireclay bricks
  • Mullite bricks
  • Magnesite bricks
Q.15

Fusion point of an acidic refractory material is

  • increased by the addition of basic oxides.
  • reduced by the addition of basic oxides.
  • not affected by the addition of basic oxides.
  • always more than 2500°C.
Q.16

PCE value (Segar cone) of superduty refractories is more thanwhich is equivalent to a temperature of __________ °C.

  • 1520
  • 1630
  • 1670
  • 1730
Q.17

Which is not an acidic refractory ?

  • Silica
  • Fireclay
  • High alumina refractory
  • Carbon black
Q.18

Pure bauxite is the best raw material for the manufacture of high alumina refractories, in which maximum alumina content can be as high as __________ percent.

  • 55
  • 70
  • 80
  • 90
Q.19

Refractoriness under loads (RUL) is quite close to the fusion temperature (PCE) for __________ bricks.

  • fireclay
  • silica
  • dolomite
  • very low alumina
Q.20

Addition of zircon to silica refractory brick improves its

  • crushing strength
  • resistance to slag attack
  • both (a) and (b)
  • neither (a) nor (b)
Q.21

silicon carbide refractories have very low

  • refractoriness (< 1700°C).
  • thermal conductivity.
  • resistance to thermal shock.
  • none of these.
Q.22

Pick out the wrong statement.

  • A ceramic material which becomes fluid upon heating and can be moulded in liquid/viscous state is termed s glass.
  • Ceramic materials do not undergo vitrification on heating.
  • Ceramic materials are brittle in nature.
  • Non-oxide ceramic materials generally act as a semi-conductor.
Q.23

__________ is not a single oxiderefractory.

  • Zirconia
  • Silicon carbide
  • Magnesia
  • None of these
Q.24

Which one contains maximum percentage of Al2O3 ?

  • Firebrick
  • Sillimanite
  • Magnesite
  • Aluminous firebrick
Q.25

Alumina-graphite bricks are used for lining the

  • slide gate in teeming laddies.
  • continuous casting systems.
  • both (a) and (b).
  • neither (a) nor (b).
Q.26

Which is required in an insulating refractory ?

  • High thermal conductivity
  • Low porosity
  • Both (a) and (b)
  • Neither (a) nor (b)
Q.27

Which of the following is not an acidic refractory ?

  • Silica bricks
  • Fireclay bricks
  • Bauxite bricks
  • Magnesia bricks
Q.28

Natural silica

  • mainly contains quartz.
  • is not stable at high temperature.
  • transforms to other allotropic forms i.e tridymite and cristoballite involving very high volume changes.
  • all (a), (b) and (c).
Q.29

Refractories subjected to alternate cycles of heating & cooling are liable to loose their resistance to

  • thermal spalling
  • slag attack
  • fusion under load
  • CO attack
Q.30

Which is a neutral refractory ?

  • Graphite
  • Magnesite chrome
  • Silica
  • Magnesia
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