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.Management Sciences
Category: Refractory Technology
Carbon refractories have very high __________________?
A. Wetting characteristics
B. Refractoriness
C. Thermal conductivity
D. Both B. and C.
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
Machine moulding of dry mixture of refractories requires a pressure of the order of _____________ kg/cm2?
A. 10
B. 100
C. 500
D. 1000
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
Pick out the wrong statement?
A. Sand & coke is the main raw material for the manufacture of silicon carbide
B. Carbon refractories cannot be used in the furnaces operating under reducing conditions
C. Mullite can be obtained by the heating of alusite, kyanite or sillimanite
D. Silica occurs in nature in all cellular, amorphous or crystalline form
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
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
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
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
Spalling resistance of a refractory cannot 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
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