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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

Spray test determines the __________ of refractories.

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

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Question 2

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

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

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Question 3

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.

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Question 4

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

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

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Question 5

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).

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Question 6

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.

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Question 7

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

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Question 8

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.

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Question 9

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

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Question 10

Hollow refractory bricks are made by

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

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Question 11

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).

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Question 12

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).

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Question 13

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.

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Question 14

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.

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Question 15

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).

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Question 16

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.

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Question 17

Grog

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

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Question 18

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

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

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Question 19

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

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Question 20

Which is not a basic refractory ?

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

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Question 21

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

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

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Question 22

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

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Question 23

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).

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Question 24

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

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

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Question 25

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

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Question 26

Chemically, mullite refractories is

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

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Question 27

Panel test determines the __________ of refractories.

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

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Question 28

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

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

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Question 29

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

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

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Question 30

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

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

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Question 31

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

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Question 32

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).

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Question 33

Which one expands on heating ?

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

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Question 34

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.

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Question 35

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.

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Question 36

Firing temperature of magnesite bricks is about __________ °C.

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

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Question 37

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

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

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Question 38

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

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Question 39

Vacuum steel degassing units are lined with

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

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Question 40

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

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

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Question 41

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

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Question 42

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)

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Question 43

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

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

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Question 44

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).

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Question 45

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

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Question 46

Refractories are dried in the

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

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Question 47

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.

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Question 48

An indication of degree of firing in silica brick is its

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

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