Carbon refractories have very high

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

A

Green strength

B

Voids

C

Shrinkage

D

Both B and C

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

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

silicon carbide refractories have very low

A

[

A. Refractoriness (

B. Thermal conductivity

B

Resistance to thermal shock

C

None of these

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

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

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

With increasing alumina content, the fusion point of high alumina refractories

A

Increases

B

Decreases

C

Remains constant

D

May increase or decrease ; depends on its alumina content

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

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

Carbon refractories have very high

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