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Refractory Technology MCQ Questions & Answers

Refractory Technology MCQs : This section focuses on the "Refractory Technology". These Multiple Choice Questions (MCQs) should be practiced to improve the Refractory Technology skills required for various interviews (campus interview, walk-in interview, company interview), placement, entrance exam and other competitive examinations.




Question 1

Grog

A. contains both alumina and silica.
B. iscrushed firebrick.
C. is a non-plastic material.
D. all (a), (b) and (c).

View Answer

Question 2

Thermal conductivity of refractory bricks

A. Increases with decrease in porosity
B. Decreases with decreases in porosity
C. Is independent of its porosity and is maximum for insulating bricks
D. Increases with the amount of air entrapped in pores

View Answer

Question 3

Quartz is

A. Stable form of silica upto 870°C
B. Converted to tridymite on firing between 870 to 1470°C
C. Transformed to crystoballite on heating above 1470°C
D. All of the above

View Answer

Question 4

Furnace atmosphere for softening temperature determination of refractories (in which segar cones are placed) should be

A. Oxidising
B. Neutral
C. Either A or B
D. Neither A nor B

View Answer

Question 5

To resist spalling tendency, a refractory should have

A. Greater diffusivity
B. Low specific heat
C. Low thermal co-efficient of expansion
D. All of the above

View Answer

Question 6

SiO₂ percentage in firebrick is about

A. 35-40
B. 55-60
C. 80-85
D. >94

View Answer

Question 7

__________ is the measure of the strength of refractory under the combined effect of temperature & load.

A. Porosity
B. RUL
C. Specific gravity
D. Thermal conductivity

View Answer

Question 8

Segar cones are used for the determination of __________ of refractories.

A. Softening temperature
B. Spalling resistance
C. Electrical conductivity
D. Resistance to slag attack

View Answer

Question 9

Mixing of ground refractory material and water is done in a __________ mill.

A. Pug
B. Ball
C. Tube
D. Rod

View Answer

Question 10

Dolomite bricks have good resistance to attack by

A. Molten steel
B. Iron oxide
C. Lime slag
D. None of these

View Answer

Question 11

Refractories are dried in the

A. rotary kilns
B. tunnel kilns
C. sun
D. none of these

View Answer

Question 12

High alumina refractory compared to fireclay bricks have

A. Less load bearing capacity
B. Less resistance to slag attack
C. Low refractoriness
D. High resistance to thermal shock and creep

View Answer

Question 13

Hot blast main (carrying air at 1000°C) in blast furnace are lined with __________ bricks.

A. Silica
B. Fireclay
C. Magnesite
D. Zirconia

View Answer

Question 14

Grog addition in fireclay during brick manufacture is done to

A. Reduce its shrinkage on heating
B. Impart greater spalling resistance
C. Enhance the strength of fired refractories
D. All of the above

View Answer

Question 15

Tar dolomite bricks are used in the

A. Basic Bessemer converter
B. Basic open hearth furnace
C. Electric furnaces
D. All of the above

View Answer

Question 16

Pyrometric cone equivalent (PCE) value (Segar cone) of 'superduty refractories' is more than 33 which corresponds to a temperature of __________ °C.

A. 1520
B. 1630
C. 1670
D. 1730

View Answer

Question 17

Maximum apparent porosity of magnesite bricks is about __________ percent.

A. 8
B. 24
C. 44
D. 58

View Answer

Question 18

Magnesite chrome bricks are used in the

A. Roof lining of basic open hearth & other basic furnaces
B. Reheating furnaces
C. Soaking pits
D. All of the above

View Answer

Question 19

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

A. Strength
B. Abrasion resistance
C. Both A & B
D. Neither A nor B

View Answer

Question 20

Spinel', a refractory mineral is chemically represented as

A. MgAl2O₄
B. MgAl2O₃
C. MgSO₄
D. MgAl2O₃.2H₂O

View Answer

Question 21

Because of its very high refractoriness of the order of __________ °C, silicon carbide refractories are used in zinc smelting furnace, muffle furnace and for supporting the wares in tunnel kilns.

A. 1800
B. 2200
C. 2400
D. 2700

View Answer

Question 22

Periclase is

A. Crystalline form of MgO
B. MgCO₃
C. ZrSO₄
D. Amorphous magnesite

View Answer

Question 23

Ganister is a source of the

A. Silica
B. Periclase
C. Lime
D. None of these

View Answer

Question 24

Upper portion of hot metal mixer are lined with mullite bricks, which helps in resisting the

A. Washing action of metal
B. Corrosion by layer of slag
C. Both A & B
D. Neither A nor B

View Answer

Question 25

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

A. Not required to resist the corrosive action of basic slag
B. Not subjected to fluctuation in temperature
C. Used for raising & maintaining high temperature
D. Both (b) and ©

View Answer

Question 26

Which of the following bricks should not be used, if the furnace is to be used intermit-tantly?

A. Firebricks
B. Silica bricks
C. Silicon carbide bricks
D. Sillimanite

View Answer

Question 27

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

A. superduty fireclay
B. silica
C. chromite
D. none of these

View Answer

Question 28

Addition of grog in fireclay brick during its manufacture is advantageous, because it results in

A. Less shrinkage in heating, decreased apparent porosity & increased specific gravity
B. High strength & thermal spalling resistance
C. Less addition of water to get a workable plasticity & lesser time required for drying the raw refractories and hence increased rate of production
D. All of the above

View Answer

Question 29

Which is not an acidic refractory?

A. Silica
B. Fireclay
C. High alumina refractory
D. Carbon black

View Answer

Question 30

Refractory castables are used for

A. Producing monolithic linings
B. Patch work
C. Minimising the number of joints in the structure
D. All of the above

View Answer

Question 31

silicon carbide refractories have very low

A. Refractoriness (< 1700°C)
B. Thermal conductivity
C. Resistance to thermal shock
D. None of these

View Answer

Question 32

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

A. Mortars
B. Cements
C. Castables
D. None of these

View Answer

Question 33

Which of the following is not an acidic refractory?

A. Silica bricks
B. Fireclay bricks
C. Bauxite bricks
D. Magnesia bricks

View Answer

Question 34

Which one contains minimum percentage of SiO₂?

A. Firebrick
B. Sillimanite
C. Semi-silica
D. Aluminous firebrick

View Answer

Question 35

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

A. segar cones.
B. muffles for muffle furnaces.
C. insulating bricks.
D. crucibles used for melting of high purity metals.

View Answer

Question 36

Which is not a natural insulating material?

A. Diatomaceous earth/kieselgur
B. Asbestos
C. Vermiculite
D. None of these

View Answer

Question 37

Porosity of fireclay refractories is __________ percent.

A. 5-10
B. 10-25
C. 25-35
D. 35-50

View Answer

Question 38

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

A. 5
B. 20
C. 40
D. 55

View Answer

Question 39

Crushing strength of a refractory

A. Increases with rise in service temperature
B. Decreases with rise in service temperature
C. Is unaffected with change in service temperature
D. Decreases with increase in porosity

View Answer

Question 40

Which form of silica has the highest specific gravity?

A. Quartz
B. Cristobalite
C. Tridymite
D. All of the above

View Answer

Question 41

Magnesite refractories have low resistance to

A. Attack by basic slag
B. Abrasion
C. Disintegration on sudden change of temperature
D. Both B and C

View Answer

Question 42

Fireclay bricks are not used in the

A. Blast furnace
B. Hot blast stove
C. Cupola
D. Wall of coke oven

View Answer

Question 43

Ceramic recuperators used for waste heat recovery from high temperature flue gas going out of the furnace is made of

A. Fireclay
B. Silicon carbide
C. Corrundum
D. Siliceous fireclay

View Answer

Question 44

Magnesite bricks have poor resistance to attack by __________ slag.

A. Lime
B. Basic
C. Acid
D. None of these

View Answer

Question 45

Pure oxide refractories are generally monocrystaliine in nature and are self bonded __________ bricks are generally used as moderator in nuclear reactors.

A. Beryllia
B. Carborundum
C. Corundum
D. Thoria

View Answer

Question 46

In panel test for spalling resistance, the average face temperature of panel assembly is maintained at __________ °C for 24 hours.

A. 700
B. 1000
C. 1600
D. 2000

View Answer

Question 47

The largest consumer of refractories is the __________ industry.

A. Cement
B. Metallurgical
C. Fertiliser
D. Power

View Answer

Question 48

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

A. Tridymite
B. Cristobalite
C. Quartz
D. None of these

View Answer

Question 49

Electrical resistor bars are made of

A. Silicon carbide
B. Alumina
C. Zirconia
D. Graphite

View Answer

Question 50

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

A. Resistance to abrasion
B. Resistance to slag peneration
C. Stability of volume at high temperature
D. Resistance to corrosion by slag

View Answer

Question 51

Firing of refractory brick is done to

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

View Answer

Question 52

__________ nozzles are used in continuous casting of steel,

A. Zircon
B. Thoria
C. Carborundum
D. Beryllia

View Answer

Question 53

Faster rate of drying of moulded refractories results in high __________ of refractories.

A. Green strength
B. Voids
C. Shrinkage
D. Both B and C

View Answer

Question 54

Semi-silica bricks compared to silica bricks have

A. Less fusion point
B. Better spalling resistance
C. Both A & B
D. Neither A nor B

View Answer

Question 55

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

A. density
B. specific heat
C. thermal conductivity
D. none of these

View Answer

Question 56

Firing temperature is minimum (1250-1400 °C) for __________ bricks.

A. fireclay
B. direct bonded basic
C. silica
D. magnesite

View Answer

Question 57

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

A. 1520-1630
B. 1630-1670
C. > 1730
D. > 2000

View Answer

Question 58

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

A. Strength
B. Thermal conductivity
C. Spalling resistance
D. None of these

View Answer

Question 59

Zircon refractories have

A. Low co-efficient of expansion
B. High RUL (1600°C) and refractoriness (> 2000°C)
C. High spalling resistance
D. All of the above

View Answer

Question 60

Which of the following is not a neutral refractory?

A. Silicon carbide
B. Magnesite
C. Chromite
D. Graphite

View Answer

Question 61

Bottom of basic open hearth furnace are constructed of

A. Dead burnt magnesite ramming mass
B. Porous fireclay bricks
C. Semi-silica bricks
D. Silicon carbide bricks

View Answer

Question 62

10 to 30% magnesite is added to chromite to produce chrome-magnesite refractories. Magnesite addition is mainly done to improve the __________ of chromite.

A. Spalling resistance
B. Refractoriness
C. Crushing strength
D. Resistance to slag

View Answer

Question 63

Cold crushing strength of a refractory does not depend upon its

A. Shape
B. Composition
C. Firing temperature
D. Texture

View Answer

Question 64

__________ is not a single oxiderefractory.

A. Zirconia
B. Silicon carbide
C. Magnesia
D. None of these

View Answer

Question 65

Porosity is induced in insulating refractories by adding

A. Powdered naphthalene
B. Ammonium chloride/sulphate
C. Calcium phosphate
D. All of the above

View Answer

Question 66

__________ of carbon blocks in the hearth of blast furnace helps in avoiding skull formation, when it becomes cold.

A. High thermal conductivity
B. Low porosity
C. Non-wetting characteristics
D. High density

View Answer

Question 67

High thermal conductivity of a refractory material is not important, when it is to be used in the

A. Coke oven regenarators
B. Muffle furnace
C. Blast furnace
D. Recuperators

View Answer

Question 68

Refractoriness under load (RUL) of fireclay bricks (under a load of 2 kg/cm² ) is __________ °C.

A. 500
B. 1000
C. >1350
D. >2000

View Answer

Question 69

An indication of degree of firing in silica brick is its

A. specific gravity
B. fusion point
C. RUL
D. none of these

View Answer

Question 70

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

A. spalling resistance.
B. refractoriness.
C. refractoriness under load (RUL).
D. none of these.

View Answer

Question 71

High porosity refractory bricks have

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

View Answer

Question 72

Which is not a high alumina refractory?

A. Mullite
B. Corrundum
C. Bauxite
D. Dolomite

View Answer

Question 73

Silica refractories are not used in

A. Coke oven walls
B. Beehive coke ovens
C. Dome and upper portion of B.F. stoves
D. Open hearth furnace roof

View Answer

Question 74

Rotary kilns meant for calcination of limestone are lined with chrome magnesite in __________ zone.

A. Preheating
B. Cooling
C. Burning
D. All of the above

View Answer

Question 75

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

A. 770
B. 570
C. 270
D. 70

View Answer

Question 76

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

A. 30
B. 50
C. 70
D. 90

View Answer

Question 77

Which one expands on heating ?

A. Silica bricks
B. Fireclay bricks
C. Both (a) & (b)
D. Neither (a) nor (b)

View Answer

Question 78

Ferromagnetic ceramic material is not used in the

A. Thermal insulation
B. Transformers
C. Magnetic switches
D. Television sets

View Answer

Question 79

Zirconia refractories are not used in

A. Making sheaths for thermocouple
B. Lining high temperature ceramic kilns
C. Furnaces subjected to fluctuating temperature
D. High frequency induction furnaces in the form of inductors

View Answer

Question 80

Chrome magnesite bricks are

A. Acidic in nature
B. Neutral in nature
C. Having higher RUL than silica bricks
D. Made by mixing 30% chromite and 70% periclase

View Answer

Question 81

Which of the following is not a high alumina refractory material?

A. Kyanite
B. Sillimanite
C. Diaspore
D. Periclase

View Answer

Question 82

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

A. not required to resist the corrosive action of basic slag.
B. not subjected to fluctuation in temperature.
C. used for raising & maintaining high temperature.
D. both (b) and (c)

View Answer

Question 83

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

A. silica
B. carborundum
C. fireclay
D. magnesite

View Answer

Question 84

Resistance to slag attack of a refractory

A. Depends on the nature of slag & refractory
B. Decreases at higher temperature
C. Decreases, if defective joints & cracks exist in the refractory
D. All of the above

View Answer

Question 85

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?

A. Cork
B. Saw dust
C. Sand
D. Chemically prepared foam

View Answer

Question 86

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

A. increases
B. decreases
C. remains same
D. may increase or decrease

View Answer

Question 87

Silica bricks are never used for lining the

A. Beehive coke ovens
B. By-product coke ovens
C. Dome of blast furnace stoves
D. Roof of open hearth furnace

View Answer

Question 88

Fireclay refractories

A. Are not resistant to the action of basic slags
B. Combine with salts (e.g. chlorides sulphates etc.) & bases (e.g. lime, magnesia etc.) forming fusible aluminates silicates etc
C. Shrink during firing
D. All of the above

View Answer

Question 89

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

A. Resistance to abrasion.
B. Resistance to slag peneration.
C. Stability of volume at high temperature.
D. Resistance to corrosion by slag.

View Answer

Question 90

Fireclay refractories have

A. Low co-efficient of thermal expansion
B. Poor thermal spalling resistance
C. Tendency to expand unduly high during firing
D. Very high cost

View Answer

Question 91

An ideal refractory should have high

A. Spalling rate
B. Fusion point
C. Shrinkage ability
D. None of these

View Answer

Question 92

Spalling of a refractory means its

A. Softening
B. Fracture due to uneven expansion at high temperature
C. Resistancce to compressive loads
D. Resistance to chemical action of gases and molten fluxes

View Answer

Question 93

Basic bricks are not made of

A. Fireclay
B. Magnesite
C. Foresterite
D. Chromite

View Answer

Question 94

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

A. 1380
B. 1520
C. 1710
D. 1915

View Answer

Question 95

Vacuum steel degassing units are lined with

A. silica bricks
B. low duty firebricks
C. high alumina bricks
D. graphite blocks

View Answer

Question 96

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

A. Hearth of the blast furnace
B. Nuclear reactors, missiles & space crafts
C. Insulation of high temperature furnaces
D. Roof of electric furnaces

View Answer

Question 97

Machine moulding of dry mixture of refractories requires a pressure of the order of __________ kg/cm².

A. 10
B. 100
C. 500
D. 1000

View Answer

Question 98

High refractorinness of refractory bricks means, that it has a

A. High spalling resistance
B. Low spalling resistance
C. High resistance to fusion
D. Low porosity

View Answer

Question 99

Addition of zircon to silica refractory brick improves its

A. Crushing strength
B. Resistance to slag attack
C. Neither A nor B
D. Neither A nor B

View Answer

Question 100

Pick out the wrong statement.

A. Electrical conductivity of refractory is not important, when these are to be used in electrical furnaces
B. Graphite and metals are the good electrical conductor among the refractories and others are all electrical insulators
C. Refractories used for lining electrical furnaces should ordinarily have very low electrical conductivity
D. Electrical conductivity of porous refractory material is low

View Answer

Question 101

Magnesite chrome refractories

A. Have better spalling resistance than chrome magnesite refractories
B. Have very low thermal co-efficient of expansion
C. Are not at all resistant to the corrosive action of iron oxide
D. Have very low (50 kg/cm² ) cold crushing strength (C.C.S.), and can not be used in metalcase form

View Answer

Question 102

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

A. Coke ovens
B. Insulation
C. Regenerators
D. Muffle furnaces

View Answer

Question 103

Hollow refractory bricks are made by

A. slip casting
B. hand moulding
C. pressing/machine moulding
D. extrusion

View Answer

Question 104

Firing of refractory brick is done to

A. Dehydrate the dried refractory
B. Develop stable mineral forms in them
C. Form ceramic bonds necessary for development of high crushing strength in the finished product
D. All of the above

View Answer

Question 105

Quartz is

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

View Answer

Question 106

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

A. oxidising atmosphere
B. reducing atmosphere
C. electric furnace
D. neutral atmosphere

View Answer

Question 107

Spalling tendency of refractories is reduced by increasing its

A. Porosity
B. Specific gravity
C. Thermal conductivity
D. Strength

View Answer

Question 108

Which one expands on heating?

A. Silica bricks
B. Fireclay bricks
C. Both A & B
D. Neither A nor B

View Answer

Question 109

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

A. 2-3
B. 5-7
C. 7-12
D. 14-20

View Answer

Question 110

Silica refractories

A. Crack when subjected to sudden change of temperature
B. Can not be used in the dome of hot blast stoves
C. Have lower thermal conductivity than fireclay bricks
D. All of the above

View Answer

Question 111

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

A. Fireclay
B. Silica
C. Dolomite
D. Very low alumina

View Answer

Question 112

Chrome magnesite is not used in the

A. Inner lining of L.D. converter
B. Aluminium melting furnaces
C. Wear out lining of steel melting furnaces
D. All of the above

View Answer

Question 113

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

A. Superduty fireclay
B. High alumina
C. Silica
D. Carborundum

View Answer

Question 114

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

A. subjected to temperature fluctuation.
B. required to resist corrosive basic slag.
C. subjected to high load.
D. none of these.

View Answer

Question 115

Thermal spalling mainly occurs during __________ of furnaces.

A. Cooling down
B. Warming up
C. Both A & B
D. Neither A nor B

View Answer

Question 116

RUL of refractories depends on the

A. Chemical composition
B. Physical structure
C. Presence of impurities like iron & alkali
D. All of the above

View Answer

Question 117

High alumina refractories are used in the

A. Dome of blast furnace stoves
B. Electric arc furnace roof
C. Glass melting furnaces
D. All of the above

View Answer

Question 118

High density refractory bricks have lower

A. Spalling resistance
B. Thermal conductivity
C. Fusion point
D. Slag penetration resistance

View Answer

Question 119

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

A. High refractoriness
B. High resistance to spalling
C. High strength and density
D. All of the above

View Answer

Question 120

Fireclay bricks are not used in the

A. beehive coke oven.
B. by-product coke oven walls.
C. combustion chamber of B.F. stoves.
D. coke oven regenerators.

View Answer

Question 121

Mullite is chemically represented by

A. Al2O₃ . 2SiO₂
B. 3Al2O₃ . 2SiO₂
C. Al2O₃ . SiO₂
D. 2Al2O₃ . 3SiO₂

View Answer

Question 122

Firing temperature of magnesite bricks is about __________ °C.

A. 800-1000
B. 1000-1200
C. 1600-1800
D. 2400-2600

View Answer

Question 123

Conversion of silica mineral to cristobalite is accompanied by reduction in its

A. Volume
B. Specific gravity
C. Both A & B
D. Neither A nor B

View Answer

Question 124

Ramming masses are used for

A. Obtaining monolithic working faces
B. Repairing construction of various furnace parts
C. Both A & B
D. Neither A nor B

View Answer

Question 125

Fireclay bricks are not used in the

A. Beehive coke oven
B. By-product coke oven walls
C. Combustion chamber of B.F. stoves
D. Coke oven regenerators

View Answer

Question 126

Chromite refractories

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

View Answer

Question 127

With increase in the density of silica refractories, its

A. Resistance to slag attack increases
B. Spalling resistance reduces
C. Both A & B
D. Neither A nor B

View Answer

Question 128

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

A. Non-wetting characteristic
B. High thermal conductivity
C. High crushing strength
D. None of these

View Answer

Question 129

Carbon bricks are not used in the lining of the

A. Combustion chamber of blast furnace stoves
B. Electric furnaces
C. Highly chemical resistant equipments
D. Blast furnace hearth

View Answer

Question 130

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

A. Fireclay
B. Carborundum
C. Graphite
D. Chromite

View Answer

Question 131

Fireclay bricks are used in the

A. Furnaces allowed to cool frequently
B. Flues
C. Chimney linings
D. All of the above

View Answer

Question 132

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

A. buckstay
B. breast wall
C. armouring
D. baffle

View Answer

Question 133

Resistance to slag attack of a refractory

A. depends on the nature of slag & refractory.
B. decreases at higher temperature.
C. decreases, if defective joints & cracks exist in the refractory.
D. all (a), (b) and (c).

View Answer

Question 134

Insulating refractories should have

A. High porosity
B. Low thermal conductivity
C. Both A & B
D. Neither A nor B

View Answer

Question 135

Chromite refractories are used in

A. Bottom of soaking pits
B. Between acid & basic linings in basic open hearth furnaces to prevent their chemical action with each other
C. Both A & B
D. Neither A nor B

View Answer

Question 136

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

A. Pottery furnace
B. Glass melting furnace
C. Crucibles
D. Gas retorts

View Answer

Question 137

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

A. 0.5
B. 1
C. 2
D. 3.5

View Answer

Question 138

Which of the following has the lowest electrical resistivity?

A. Graphite
B. Fireclay
C. Alumina
D. Zircon

View Answer

Question 139

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

A. fireclay
B. silica
C. chrome magnesite
D. zirconia

View Answer

Question 140

Which brick undergoes maximum shrinkage on drying?

A. Tar bonded dolomite bricks
B. Fireclay bricks
C. Magnesite bricks
D. Chromite bricks

View Answer

Question 141

Grog

A. Contains both alumina and silica
B. Iscrushed firebrick
C. Is a non-plastic material
D. All of the above

View Answer

Question 142

Slide gates in teeming laddie used for steel pouring in ingot moulds is lined with __________ bricks.

A. Bakelite impregnated or fused periclase
B. Silica
C. Semi-silica
D. Fireclay

View Answer

Question 143

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

A. Very high temperatures are involved
B. Highly reducing conditions are involved
C. Presence of iron or silica is harmful
D. All of the above

View Answer

Question 144

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

A. 80 and 20
B. 20 and 80
C. 50 and 50
D. 60 and 40

View Answer

Question 145

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

A. Soaking pit
B. Blastfurnace
C. L.D. converter
D. Coke ovens

View Answer

Question 146

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

A. Tar bonded dolomite bricks
B. Fireclay bricks
C. Mullite bricks
D. Magnesite bricks

View Answer

Question 147

Bauxite calcining rotary kilns are lined with __________ bricks.

A. Fireclay
B. Carbon
C. 85% alumina
D. Corundum

View Answer

Question 148

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.

A. 55
B. 70
C. 80
D. 90

View Answer

Question 149

Pick out the wrong statement.

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

View Answer

Question 150

Which is a neutral refractory?

A. Graphite
B. Magnesite chrome
C. Silica
D. Magnesia

View Answer

Question 151

Lower wall courses of soaking pits are made of __________ bricks to avoid the action of molten slag & scale.

A. Chrome or magnesite
B. Silicon carbide
C. Silica
D. Lowduty fireclay

View Answer

Question 152

Cermets are

A. Composite material containing both ceramic & metallic constituents
B. Having high strength & resistance to high temperature
C. Used in space vehicles, missiles & nuclear energy plants
D. All of the above

View Answer

Question 153

Pick out the wrong statement.

A. Refractories used in muffle furnace should have low thermal conductivity
B. The electrical resistivity of refractories drops rapidly with rise in temperature
C. For reducing spalling tendency, the refractory should be well fired and its porosity should be more
D. Refractoriness under load (RUL) of a refractory is always less than its refractoriness

View Answer

Question 154

Which is not a basic refractory?

A. Chrome magnesite
B. Magnesite
C. Dolomite
D. Silicon carbide

View Answer

Question 155

Spalling resistance of a refractory can not be increased by

A. Increasing its porosity
B. Using a coarser grog during its manufacture
C. Decreasing its thermal co-efficient of expansion
D. Making it denser

View Answer

Question 156

Carbon refractories have very high

A. Wetting characteristics
B. Refractoriness
C. Thermal conductivity
D. Both B and C

View Answer

Question 157

Zirconia refractory

A. Does not react with basic slags
B. Is produced from baddeleyite
C. Can not be used as an insulator
D. Has poor electrical conductivity at high temperature

View Answer

Question 158

Carbon refractory blocks

A. Are wetted by molten iron
B. Are used in the hearth of blast furnace
C. Are acidic in nature
D. All of the above

View Answer

Question 159

Which is not an alumino-silicate refractory?

A. Fireclay bricks
B. Mullite bricks
C. Tar dolomite bricks
D. High alumina bricks

View Answer

Question 160

The main raw material for manufacture of silicon carbide refractories is

A. Corrundum
B. Carborundum
C. Bauxite
D. Periclase

View Answer

Question 161

Chemically, mullite refractories is

A. 3Al2O₃.2SiO₂
B. Al2O₃
C. ZrSO₄
D. ThO₂

View Answer

Question 162

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

A. high duty fireclay
B. silica
C. mullite
D. carborundum

View Answer

Question 163

Spray test determines the __________ of refractories.

A. resistance to slag penetration
B. resistance to CO attack
C. RUL
D. permanent linear change

View Answer

Question 164

Magnesite refractories are generally not used in the

A. Electric furnace walls
B. Steel melting furnace
C. Open hearth furnace
D. Burning zone of cement kilns

View Answer

Question 165

PCE value (Segar cone) of superduty refractories is more than 33, which is equivalent to a temperature of __________ °C.

A. 1520
B. 1630
C. 1670
D. 1730

View Answer

Question 166

Fusion point of an acidic refractory material is

A. Increased by the addition of basic oxides
B. Reduced by the addition of basic oxides
C. Not affected by the addition of basic oxides
D. Not affected by the addition of basic oxides

View Answer

Question 167

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

A. Alumina
B. Thoria
C. Zirconia
D. Magnesia

View Answer

Question 168

Rate of slag attack on refractories increases with rise in temperature due to the

A. Decreased viscosity of slag
B. Increased thermal conductivity of brick
C. Oxidising condition in the furnace
D. None of these

View Answer

Question 169

The linear thermal expansion of __________ bricks upto 1000 °C is very low of the order of ≤ 0.5 percent.

A. Fireclay
B. Silica
C. Magnesite
D. Corundum

View Answer

Question 170

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

A. hearth of the blast furnace.
B. nuclear reactors, missiles & space crafts.
C. insulation of high temperature furnaces.
D. roof of electric furnaces.

View Answer

Question 171

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

A. Thermal spalling
B. Slag attack
C. Fusion under load
D. CO attack

View Answer

Question 172

Which is not a basic refractory ?

A. Chrome magnesite
B. Magnesite
C. Dolomite
D. Silicon carbide

View Answer

Question 173

Pick out the wrong statement.

A. Fluxing material like lime is added in clay to reduce the vitrification temperature
B. Main constituents of clay are alumina and silica
C. Addition of sand in ceramic materials makes it non-plastic, increases its fusion point and reduces its shrinkage on burning
D. Vitrification of fireclay material is done to increase its porosity

View Answer

Question 174

Chemically, mullite refractories is

A. 3Al2O3.2SiO2
B. Al2O3
C. ZrSO4
D. ThO2

View Answer

Question 175

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 ?

A. Cork
B. Saw dust
C. Sand
D. Chemically prepared foam

View Answer

Question 176

Pick out the wrong statement.

A. Insulating refractories used in place of regular refractory bricks are usually called light weight refractories, and they have similar composition as heavy bricks
B. Graphite refractories are also called plumbago refractories
C. Superduty fireclay bricks correspond to a pyrometric cone equivalent of 26-28
D. Calcined magnesite is also called dead burnt magnesite

View Answer

Question 177

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

A. Aluminium phosphate
B. Water
C. Lime
D. Plaster of paris

View Answer

Question 178

Refractoriness under load (RUL) is the most important property for the refractory bricks

A. At the hearth bottom of the furnace on which stock is placed
B. Used for furnace insulation
C. Used in the roof of the furnace
D. None of these

View Answer

Question 179

Maximum shrinkage in volume occurring during burning/firing of dried refractories may be as high as __________ percent.

A. 10
B. 15
C. 20
D. 30

View Answer

Question 180

Thoria

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

View Answer

Question 181

Which of the following does not occur during firing/burning of refractories?

A. Removal of water of hydration
B. Vitrification
C. Decrease in crushing strength
D. Development of stable mineral form

View Answer

Question 182

The highest melting pure oxide (m.p. > 3000°C) is

A. Thoria
B. Alumina
C. Beryllia
D. Zirconia

View Answer

Question 183

__________ bricks are used in the burning zone of a cement rotary kiln.

A. High alumina
B. Fireclay
C. Thoria
D. Silicon carbide

View Answer

Question 184

Chromite refractories are

A. Acidic refractory
B. Neutral refractory
C. Basic refractory
D. Fired at a temperature of 600°C only

View Answer

Question 185

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

A. 45
B. 60
C. 80
D. 95

View Answer

Question 186

Fireclay bricks are never used in the

A. Beehive oven
B. Coke oven walls
C. Zinc roaster
D. Lead blast furnace

View Answer

Question 187

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

A. Cristobalite
B. Tridymite
C. Quartz
D. None of these

View Answer

Question 188

Fusion point of a basic refractory material is

A. Reduced by the addition of acid oxides
B. Increased by the addition of acid oxides
C. Not affected by the addition of acid oxides
D. Always less than 1000°C

View Answer

Question 189

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

A. 1350
B. 1715
C. 2570
D. 2800

View Answer

Question 190

Alumina-graphite bricks are used for lining the

A. Slide gate in teeming laddies
B. Continuous casting systems
C. Both A & B
D. Neither A nor B

View Answer

Question 191

Super refractories' are made from pure

A. Carbides
B. Oxides
C. Borides
D. Nitrides

View Answer

Question 192

Pick out the wrong statement.

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

View Answer

Question 193

Maximum safe working temperature for fireclay bricks is about __________ °C.

A. 1150
B. 1300
C. 1450
D. 1550

View Answer

Question 194

Cold crushing strength of ordinary fireclay brick is about 950 kg/cm² . On exposure to a temperature of about 1500°C, its crushing strength may come down to as low as __________ kg/cm² .

A. 450
B. 250
C. 150
D. 65

View Answer

Question 195

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

A. Quartz
B. Cristobalite
C. Tridymite
D. None of these

View Answer

Question 196

Which is a basic refractory?

A. Fireclay
B. Silica
C. Chrome magnesite
D. None of these

View Answer

Question 197

Natural silica

A. Mainly contains quartz
B. Is not stable at high temperature
C. Transforms to other allotropic forms i.e tridymite and cristoballite involving very high volume changes
D. All of the above

View Answer

Question 198

Refractory bricks having lower porosity have

A. High insulating properties
B. Low heat capacity
C. Low thermal conductivity
D. Greater strength

View Answer

Question 199

Which of the following bricks has the most close values of RUL and PCE?

A. Silica bricks
B. Fireclay bricks
C. High alumina bricks
D. Tar dolomite bricks

View Answer

Question 200

Which is an acidic refractory?

A. Magnesite
B. Dolomite
C. Fireclay
D. Chrome magnesite

View Answer

Question 201

Chrome magnesite bricks are used in the

A. Side walls of soaking pits and arc furnaces
B. Copper melting furnaces & converters
C. Burner block of glass tanks
D. All of the above

View Answer

Question 202

Tar bonded dolomite bricks

A. Are stored under controlled temperature & humidity to avoid hydration
B. Are used in outer lining of L.D. converters
C. Have poorer hydration resistance than pitch bonded bricks
D. All of the above

View Answer

Question 203

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

A. Spalling resistance
B. Refractoriness
C. Refractoriness under load (RUL)
D. None of these

View Answer

Question 204

Silicon carbide refractories are used in the

A. Muffle furnace
B. Zinc smelting furnace
C. Ceramic recuperators
D. All of the above

View Answer

Question 205

RUL of refractories depends on the

A. chemical composition.
B. physical structure.
C. presence of impurities like iron & alkali.
D. all (a), (b) and (c).

View Answer

Question 206

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

A. Subjected to temperature fluctuation
B. Required to resist corrosive basic slag
C. Subjected to high load
D. None of these

View Answer

Question 207

__________ bricks should not be used in oxidising atmosphere.

A. Tar dolomite
B. Carbon
C. Silica
D. Fireclay

View Answer

Question 208

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

A. 1380
B. 1520
C. 1710
D. 1915

View Answer

Question 209

Cold crushing strength of fireclay bricks is about __________ kgf/cm².

A. 50-100
B. 100-150
C. 200-400
D. 500-1000

View Answer

Question 210

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

A. Segar cones
B. Muffles for muffle furnaces
C. Insulating bricks
D. Crucibles used for melting of high purity metals

View Answer

Question 211

Dilatometer is used for the determination of __________ of refractories.

A. Modulus of rupture
B. Permanent linear change
C. Resistance to CO attack
D. RUL

View Answer

Question 212

Roof of a basic open hearth furnace is lined with __________ bricks.

A. Silica
B. Fireclay
C. Dolomite
D. Magnesite

View Answer

Question 213

Periclase refractory contains mainly

A. CaO
B. MgO
C. Al2O₃
D. SiO₂

View Answer

Question 214

Carbon refractories are exclusively used in the

A. Hearth of blast furnace
B. Walls of coke oven
C. Regenerators of coke oven
D. Side wall of soaking pits

View Answer

Question 215

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

A. Quartz
B. Cristobalite
C. Tridymite
D. None of these

View Answer

Question 216

Pyrometric cone equivalent (PCE) of a refractory is the measure of its

A. Spalling resistance
B. Fusion point
C. Resistance to slag penetration
D. Resistance to carbon monoxide attack

View Answer

Question 217

Fireclay bricks is not used for lining the

A. Cupola
B. Gas producer
C. Bottom of hot metal mixer
D. Roof of open hearth furnace

View Answer

Question 218

Porosity of silica bricks varies from __________ percent.

A. 5 to 10
B. 20 to 30
C. 45 to 60
D. 60 to 75

View Answer

Question 219

Which one contains maximum percentage of Al2O₃ ?

A. Firebrick
B. Sillimanite
C. Magnesite
D. Aluminous firebrick

View Answer

Question 220

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

A. increases
B. decreases
C. remains same
D. may increase or decrease

View Answer

Question 221

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

A. cost
B. electrical conductivity
C. thermal conductivity
D. fusion point

View Answer

Question 222

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

A. Very high thermal conductivity
B. High co-efficient of expansion upto this temperature
C. High thermal diffusivity
D. Low refractoriness

View Answer

Question 223

Fusion point of a basic refractory material is

A. reduced by the addition of acid oxides.
B. increased by the addition of acid oxides.
C. not affected by the addition of acid oxides.
D. always less than 1000°C.

View Answer

Question 224

Graphite or carbon refractories

A. Exihibit wetting characteristics
B. Should be used in neutral or reducing atmosphere
C. Exhibit high shrinkage on thermal treatment
D. Are not resistant to corrosion by slag

View Answer

Question 225

Which of the following impurities reduces the refractoriness of magnesite bricks?

A. Al2O₃
B. CaO
C. SiO₂
D. All of the above

View Answer

Question 226

Carborundum used for making crucibles for melting non-ferrous metals is chemically

A. Silicon carbide
B. Silicon nitride
C. Crystalline magnesia
D. Zirconium sulphate

View Answer

Question 227

Carbon refractories

A. Do not burn/oxidise, when exposed to air on heating
B. Are not attacked by slags, as they are not wetted by melts
C. Do not resist temperature fluctuations
D. Have extremely low thermal & electrical conductivities

View Answer

Question 228

Chrome magnesite brick is not used for lining the

A. Hearth of soaking pits
B. Bottom hearth of reheating furnace
C. Coke oven regenerator
D. Burning zone of limestone rotary kilns

View Answer

Question 229

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

A. Soaking pits
B. Ceheating furnace
C. L.D. converter
D. Rotary lime kiln

View Answer

Question 230

Sillimanite is a __________ refractory.

A. Basic
B. Neutral
C. High alumina
D. Insulating

View Answer

Question 231

Fireclay bricks are used in the

A. coke ovens regenerator.
B. outer lining of L.D. converter.
C. hearth bottom of blast furnace.
D. coke oven walls.

View Answer

Question 232

High porosity refractory bricks have

A. Poor resistance to the peneration of molten slag, metal & flue gases
B. Poor heat conductivity & low strength
C. Better thermal spalling resistance
D. All of the above

View Answer

Question 233

With increase in the alumina content in firebricks, its fusion point (refractoriness)

A. Decreases linearly
B. Remains unchanged
C. Increases
D. Decreases

View Answer

Question 234

Refractory materials are never used in the construction of

A. Segar cones
B. Orton cones
C. Pressure vessels
D. Ovens & retorts

View Answer

Question 235

Permeability of bricks is a measure of the

A. Refractoriness
B. Melting point
C. Rate at which a fluid will pass through the pores
D. Expansion during heating

View Answer

Question 236

What is Thoria?

A. Thoria Has high fusion temperature (> 3000°C) but poor resistance to thermal shock
B. Thoria Has high resistance to basic slags
C. Which is expensive & radioactive, is used in crucibles for melting high purity metals
D. All of the above

View Answer

Question 237

Panel test determines the __________ of refractories.

A. fusion point
B. spalling resistance
C. slag penetration resistance
D. refractoriness under load (RUL)

View Answer

Question 238

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

A. non-wetting characteristic.
B. high thermal conductivity.
C. high crushing strength.
D. none of these.

View Answer

Question 239

Which is required in an insulating refractory?

A. High thermal conductivity
B. Low porosity
C. Both A & B
D. Neither A nor B

View Answer

Question 240

Colour of fireclay bricks is

A. Light buff to reddish buff
B. Yellow
C. Black
D. None of these

View Answer

Question 241

Refractory bricks with lower permeability is produced by using

A. Higher firing temperature
B. Higher moulding pressure
C. Finer grog size
D. All of the above

View Answer

Question 242

Cold crushing strength of refractories depends upon its

A. Composition
B. Texture
C. Firing temperature
D. All of the above

View Answer