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Quiz 6
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Q.1
Magnesite chrome bricks are used in the
Roof lining of basic open hearth & other basic furnaces
Reheating furnaces
Soaking pits
All of the above
Q.2
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.3
Outer combustion chamber of blast furnace stove is lined with __________ bricks.
Fireclay
Silica
Chrome magnesite
Zirconia
Q.4
Which is required in an insulating refractory?
High thermal conductivity
Low porosity
Both A & B
Neither A nor B
Q.5
Mixing of ground refractory material and water is done in a __________ mill.
Pug
Ball
Tube
Rod
Q.6
Roof of a basic electric furnace is made of __________ bricks.
Superduty fireclay
Silica
Chromite
None of these
Q.7
Highest melting (m.p = 3070°C) oxide refractory is
Alumina
Thoria
Zirconia
Magnesia
Q.8
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
Not affected by the addition of basic oxides
Q.9
Which of the following bricks has the most close values of RUL and PCE?
Silica bricks
Fireclay bricks
High alumina bricks
Tar dolomite bricks
Q.10
__________ is the measure of the strength of refractory under the combined effect of temperature & load.
Porosity
RUL
Specific gravity
Thermal conductivity
Q.11
Hot metal runner in blast furnace are lined with __________ bricks.
Silica
Carborundum
Fireclay
Magnesite
Q.12
Which of the following is not a high alumina refractory material?
Kyanite
Sillimanite
Diaspore
Periclase
Q.13
Magnesite refractories are generally not used in the
Electric furnace walls
Steel melting furnace
Open hearth furnace
Burning zone of cement kilns
Q.14
Silica bricks are never used for lining the
Beehive coke ovens
By-product coke ovens
Dome of blast furnace stoves
Roof of open hearth furnace
Q.15
An indication of degree of firing in silica brick is its
Specific gravity
Fusion point
RUL
None of these
Q.16
Pick out the wrong statement.
Electrical conductivity of refractory is not important, when these are to be used in electrical furnaces
Graphite and metals are the good electrical conductor among the refractories and others are all electrical insulators
Refractories used for lining electrical furnaces should ordinarily have very low electrical conductivity
Electrical conductivity of porous refractory material is low
Q.17
High refractorinness of refractory bricks means, that it has a
High spalling resistance
Low spalling resistance
High resistance to fusion
Low porosity
Q.18
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.19
Cold crushing strength of fireclay bricks is about __________ kgf/cm².
50-100
100-150
200-400
500-1000
Q.20
Maximum apparent porosity of magnesite bricks is about __________ percent.
8
24
44
58
Q.21
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 of the above
Q.22
Tar dolomite bricks are used in the
Basic Bessemer converter
Basic open hearth furnace
Electric furnaces
All of the above
Q.23
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 nor B
Q.24
Segar cones are used for the determination of __________ of refractories.
Softening temperature
Spalling resistance
Electrical conductivity
Resistance to slag attack
Q.25
Which of the following does not occur during firing/burning of refractories?
Removal of water of hydration
Vitrification
Decrease in crushing strength
Development of stable mineral form
Q.26
Rate of slag attack on refractories increases with rise in temperature due to the
Decreased viscosity of slag
Increased thermal conductivity of brick
Oxidising condition in the furnace
None of these
Q.27
Pick out the wrong statement.
Fluxing material like lime is added in clay to reduce the vitrification temperature
Main constituents of clay are alumina and silica
Addition of sand in ceramic materials makes it non-plastic, increases its fusion point and reduces its shrinkage on burning
Vitrification of fireclay material is done to increase its porosity
Q.28
Refractory castables are used for
Producing monolithic linings
Patch work
Minimising the number of joints in the structure
All of the above
Q.29
Silliminite (Al2O₃.SiO₂) refractory, which is a neutral refractory, is not used in
Pottery furnace
Glass melting furnace
Crucibles
Gas retorts
Q.30
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
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