Q.1

Which furnace consumes maximum refractory annually in an integrated steel plant ?

  • Soaking pit
  • Blastfurnace
  • L.D. converter
  • Coke ovens
Q.2

Use of higher percentage of lime for bonding silica bricks, reduces their

  • strength
  • abrasion resistance
  • both (a) & (b)
  • neither (a) nor (b)
Q.3

Magnesite refractories have low resistance to

  • attack by basic slag.
  • abrasion.
  • disintegration on sudden change of temperature.
  • both (b) and (c).
Q.4

Highest melting (m.p = 3070°C) oxide refractory is

  • alumina
  • thoria
  • zirconia
  • magnesia
Q.5

Maximum apparent porosity of magnesite bricks is about __________ percent.

  • 8
  • 24
  • 44
  • 58
Q.6

Which brick undergoes maximum shrinkage on drying ?

  • Tar bonded dolomite bricks
  • Fireclay bricks
  • Magnesite bricks
  • Chromite bricks
Q.7

The main raw material for manufacture of silicon carbide refractories is

  • corrundum
  • carborundum
  • bauxite
  • periclase
Q.8

Fireclay bricks are used in the

  • furnaces allowed to cool frequently
  • flues
  • chimney linings
  • all (a), (b) and (c)
Q.9

Lower part of hot metal mixer are lined with __________ bricks.

  • superduty fireclay
  • high alumina
  • silica
  • carborundum
Q.10

Grog addition in fireclay during brick manufacture is done to

  • reduce its shrinkage on heating.
  • impart greater spalling resistance.
  • enhance the strength of fired refractories.
  • all (a), (b) and (c).
Q.11

Which property is important for bricks used in the combustion chamber & dome of blast furnace stoves ?

  • High refractoriness.
  • High resistance to spalling.
  • High strength and density.
  • All (a), (b) and (c).
Q.12

Chrome magnesite brick is not used for lining the

  • hearth of soaking pits.
  • bottom hearth of reheating furnace.
  • coke oven regenerator.
  • burning zone of limestone rotary kilns.
Q.13

Which one contains minimum percentage of SiO2?

  • Firebrick
  • Sillimanite
  • Semi-silica
  • Aluminous firebrick
Q.14

Dilatometer is used for the determination of __________ of refractories.

  • modulus of rupture
  • permanent linear change
  • resistance to CO attack
  • RUL
Q.15

Which is the stable form of silica upto 1470°C ?

  • Quartz
  • Cristobalite
  • Tridymite
  • None of these
Q.16

Chromite refractories are used in

  • bottom of soaking pits.
  • between acid & basic linings in basic open hearth furnaces to prevent their chemical action with each other.
  • both (a) & (b)
  • neither (a) and (b)
Q.17

Carbon refractories have very high

  • wetting characteristics
  • refractoriness
  • thermal conductivity
  • both (b) and (c)
Q.18

Pick out the wrong statement.

  • Sand & coke is the main raw material for the manufacture of silicon carbide.
  • Carbon refractories can not be used in the furnaces operating under reducing conditions.
  • Mullite can be obtained by the heating of alusite, kyanite or silimanite.
  • Silica occurs in nature in all cellular, amorphous or crystalline form.
Q.19

The maximum linear expansion of silica bricks during firing is about __________ percent.

  • 0.5
  • 1
  • 2
  • 3.5
Q.20

With decrease in porosity, the __________ of the refractories decreases.

  • strength
  • thermal conductivity
  • spalling resistance
  • none of these
Q.21

Hot face insulating linings of high purity alumina fused mullite are used, where

  • very high temperatures are involved.
  • highly reducing conditions are involved.
  • presence of iron or silica is harmful.
  • all (a), (b) and (c).
Q.22

Which of the following has the lowest electrical resistivity ?

  • Graphite
  • Fireclay
  • Alumina
  • Zircon
Q.23

Dry mix hydraulic compositions of refractory aggregates with suitable bonding materials are called refractory

  • mortars
  • cements
  • castables
  • none of these
Q.24

Silica bricks have low spalling resistance below 600°C, due to its

  • very high thermal conductivity.
  • high co-efficient of expansion upto this temperature.
  • high thermal diffusivity.
  • low refractoriness.
Q.25

Thermal diffusivity of a refractory brick is high, when its __________ is high.

  • density
  • specific heat
  • thermal conductivity
  • none of these
Q.26

Which one expands on heating ?

  • Silica bricks
  • Fireclay bricks
  • Both (a) & (b)
  • Neither (a) nor (b)
Q.27

High porosity refractory bricks have

  • poor resistance to the peneration of molten slag, metal & flue gases.
  • poor heat conductivity & low strength.
  • better thermal spalling resistance.
  • all (a), (b) and (c).
Q.28

Walls, roofs & combustion chambers of annealing furnaces are made of __________ bricks.

  • high duty fireclay
  • silica
  • mullite
  • carborundum
Q.29

Refractoriness of a typical silica brick corresponds to Segar cone number, '32', which is equivalent to a temperature of __________ °C.

  • 1380
  • 1520
  • 1710
  • 1915
Q.30

Panel test determines the __________ of refractories.

  • fusion point
  • spalling resistance
  • slag penetration resistance
  • refractoriness under load (RUL)
0 h : 0 m : 1 s