Q.1

Refractoriness/fusion points of 'superduty' refractories is __________ °C.

  • 1520-1630
  • 1630-1670
  • > 1730
  • > 2000
Q.2

Vacuum steel degassing units are lined with

  • silica bricks
  • low duty firebricks
  • high alumina bricks
  • graphite blocks
Q.3

Fireclay bricks are used in the

  • coke ovens regenerator.
  • outer lining of L.D. converter.
  • hearth bottom of blast furnace.
  • coke oven walls.
Q.4

Beryllia (which is used in making crucibles for melting uranium & thorium) is superior to alumina in all respects for high temperature (> 1900°C ) use, except

  • cost
  • electrical conductivity
  • thermal conductivity
  • fusion point
Q.5

Fireclay bricks are not used in the

  • beehive coke oven.
  • by-product coke oven walls.
  • combustion chamber of B.F. stoves.
  • coke oven regenerators.
Q.6

Outer combustion chamber of blast furnace stove is lined with __________ bricks.

  • fireclay
  • silica
  • chrome magnesite
  • zirconia
Q.7

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

  • 1520
  • 1630
  • 1670
  • 1730
Q.8

Which is the stable form of silica below 870°C ?

  • Tridymite
  • Cristobalite
  • Quartz
  • None of these
Q.9

Water content in ground refractory material to be shaped into bricks by hand moulding is about __________ percent.

  • 5
  • 20
  • 40
  • 55
Q.10

An insulating refractory brick should have high porosity and low thermal conductivity. Which of the following is not used for inducing porosity in the insulating refractory bricks during its manufacture ?

  • Cork
  • Saw dust
  • Sand
  • Chemically prepared foam
Q.11

Fusion point of a basic refractory material is

  • reduced by the addition of acid oxides.
  • increased by the addition of acid oxides.
  • not affected by the addition of acid oxides.
  • always less than 1000°C.
Q.12

RUL of refractories depends on the

  • chemical composition.
  • physical structure.
  • presence of impurities like iron & alkali.
  • all (a), (b) and (c).
Q.13

With increase in the alumina content, the refractoriness of high alumina refractories

  • increases
  • decreases
  • remains same
  • may increase or decrease
Q.14

Resistance to slag attack of a refractory

  • depends on the nature of slag & refractory.
  • decreases at higher temperature.
  • decreases, if defective joints & cracks exist in the refractory.
  • all (a), (b) and (c).
Q.15

Presence of MgO in alumino-silicate refractories __________ its refractoriness.

  • increases
  • lowers
  • does not affect
  • either (a) or (b); depends on its quantity
Q.16

Chromite refractories

  • are bonded with lime and clay.
  • (free from silica) have better thermal fatigue resistance than silica and magnesite refractories.
  • are resistant to basic slag.
  • all (a), (b) and (c).
Q.17

Firing of refractory brick is done to

  • dehydrate the dried refractory.
  • develop stable mineral forms in them.
  • form ceramic bonds necessary for development of high crushing strength in the finished product.
  • all (a), (b) and (c).
Q.18

Which is the stable form of silica between 1470°C and the melting point 1713°C ?

  • Cristobalite
  • Tridymite
  • Quartz
  • None of these
Q.19

A steel member used in the furnace construction to take the thrust of the brickwork is called

  • buckstay
  • breast wall
  • armouring
  • baffle
Q.20

Grog

  • contains both alumina and silica.
  • iscrushed firebrick.
  • is a non-plastic material.
  • all (a), (b) and (c).
Q.21

Capacity of a refractory brick to withstand-sudden changes in temperature is denoted by the property called

  • spalling resistance.
  • refractoriness.
  • refractoriness under load (RUL).
  • none of these.
Q.22

Spalling of silica bricks occurs due to abrupt volume changes, when it is cooled below a temperature of __________ °C.

  • 770
  • 570
  • 270
  • 70
Q.23

Firing temperature is minimum (1250-°C) for __________ bricks.

  • fireclay
  • direct bonded basic
  • silica
  • magnesite
Q.24

Chemically, mullite refractories is

  • 3Al2O3.2SiO2
  • Al2O3
  • ZrSO4
  • ThO2
Q.25

Refractories are dried in the

  • rotary kilns
  • tunnel kilns
  • sun
  • none of these
Q.26

Skull is not formed on the carbon blocks in the hearth of a blast furnace, when it becomes cold, becaus of its

  • non-wetting characteristic.
  • high thermal conductivity.
  • high crushing strength.
  • none of these.
Q.27

With increase in the porosity, thermal spalling resistance of fireclay brick

  • increases
  • decreases
  • remains same
  • may increase or decrease
Q.28

Thoria is an expensive refractory material and is radioactive in nature. Thorium oxide is used in the manufacture of

  • segar cones.
  • muffles for muffle furnaces.
  • insulating bricks.
  • crucibles used for melting of high purity metals.
Q.29

Test piece for determination of RUL of a refractory is heated in a/an

  • oxidising atmosphere
  • reducing atmosphere
  • electric furnace
  • neutral atmosphere
Q.30

Magnesite bricks are used in those parts of furnaces, which are

  • subjected to temperature fluctuation.
  • required to resist corrosive basic slag.
  • subjected to high load.
  • none of these.
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