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.Management Sciences
Category: Refractory Technology
Refractory bricks with lower permeability is produced by using __________________?
A. Higher firing temperature
B. Higher moulding pressure
C. Finer grog size
D. All A., B. and C.
Dolomite bricks have good resistance to attack by_____________________?
A. Molten steel
B. Iron oxide
C. Lime slag
D. None of these
Highest melting (m.p = 3070°C) oxide refractory is__________________?
A. Alumina
B. Thoria
C. Zirconia
D. Magnesia
Zircon refractories have__________________?
A. Low co-efficient of expansion
B. High RUL (1600°C) and refractoriness (> 2000°C)
C. High spalling resistance
D. All A., B. and C.
An indication of degree of firing in silica brick is its____________________?
A. Specific gravity
B. Fusion point
C. RUL
D. None of these
Skull is not formed on the carbon blocks in the hearth of a blast furnace, when it becomes cold, because of its_______________?
A. Non-wetting characteristic
B. High thermal conductivity
C. High crushing strength
D. None of these
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
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 A., B. and C.
Segar cones are used for the determination of ____________ of refractories?
A. Softening temperature
B. Spalling resistance
C. Electrical conductivity
D. Resistance to slag attack
Which is not an alumino-silicate refractory ?
A. Fireclay bricks
B. Mullite bricks
C. Tar dolomite bricks
D. High alumina bricks
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