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.Management Sciences
Category: Refractory Technology
The maximum linear expansion of silica bricks during firing is about ______________ percent?
A. 0.5
B. 1
C. 2
D. 3.5
Silica bricks are attacked by basic slags at high temperature. Which of the following is not used solely as a binding material ?
A. Aluminium phosphate
B. Water
C. Lime
D. Plaster of Paris
Pick out the wrong statement ?
A. Refractories used in muffle furnace should have low thermal conductivity
B. The electrical resistivity of refractories drops rapidly with rise in temperature
C. For reducing spalling tendency, the refractory should be well fired and its porosity should be
more
D. Refractoriness under load (RUL) of a refractory is always less than its refractoriness
_____________ is not a single oxide-refractory?
A. Zirconia
B. Silicon carbide
C. Magnesia
D. None of these
Spray test determines the _____________ of refractories?
A. Resistance to slag penetration
B. Resistance to CO attack
C. RUL
D. Permanent linear change
Firing of refractory brick is done to __________________?
A. Dehydrate the dried refractory
B. Develop stable mineral forms in them
C. Form ceramic bonds necessary for development of high crushing strength in the finished
product
D. All A., B. and C.
Which is the stable form of silica between 1470°C and the melting point 1713°C ?
A. Cristobalite
B. Tridymite
C. Quartz
D. None of these
Chrome magnesite is not used in the ____________________?
A. Inner lining of L.D. converter
B. Aluminium melting furnaces
C. Wear out lining of steel melting furnaces
D. All A., and B. and C.
High porosity refractory bricks have _______________?
A. Poor resistance to the penetration of molten slag, metal & flue gases
B. Poor heat conductivity & low strength
C. Better thermal spalling resistance
D. All A., B. and C.
Thermal diffusivity of a refractory brick is high, when its ____________ is high?
A. Density
B. Specific heat
C. Thermal conductivity
D. None of these
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