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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.
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