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.Management Sciences
Category: Refractory Technology
With decrease in porosity, the ______________ of the refractories decreases?
A. Strength
B. Thermal conductivity
C. Spalling resistance
D. None of these
To resist spalling tendency, a refractory should have________________?
A. Greater diffusivity
B. Low specific heat
C. Low thermal co-efficient of expansion
D. All A., B. and C.
Upper portion of hot metal mixer are lined with mullite bricks, which helps in resisting the_________________?
A. Washing action of metal
B. Corrosion by layer of slag
C. Both A. & B.
D. Neither A. nor B.
Hot face insulating linings of high purity alumina fused mullite are used, where_________________?
A. Very high temperatures are involved
B. Highly reducing conditions are involved
C. Presence of iron or silica is harmful
D. All A., B. and C.
Pick out the wrong statement?
A. Fluxing material like lime is added in clay to reduce the vitrification temperature
B. Main constituents of clay are alumina and silica
C. Addition of sand in ceramic materials makes it non-plastic, increases its fusion point and
reduces its shrinkage on burning
D. Vitrification of fireclay material is done to increase its porosity
Thermal conductivity of refractory bricks_________________?
A. Increases with decrease in porosity
B. Decreases with decreases in porosity
C. Is independent of its porosity and is maximum for insulating bricks
D. Increases with the amount of air entrapped in pores
High thermal conductivity of a refractory material is not important, when it is to be used in the______________________?
A. Coke oven regenerators
B. Muffle furnace
C. Blast furnace
D. Recuperators
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.
Bottom of basic open hearth furnace are constructed of__________________?
A. Dead burnt magnesite ramming mass
B. Porous fireclay bricks
C. Semi-silica bricks
D. Silicon carbide bricks
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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