1) Roof of a basic open hearth furnace is lined with ______________ bricks? a. Silica b. Fireclay c. Dolomite d. Magnesite
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2) Chrome magnesite bricks are used in the_________________? a. Side walls of soaking pits and arc furnaces b. Copper melting furnaces & converters c. Burner block of glass tanks d. All A., B. and C.
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3) Refractory materials are never used in the construction of _________________? a. Segar cones b. Orton cones c. Pressure vessels d. Ovens & retorts
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4) Graphite or carbon refractories______________________? a. Exhibit wetting characteristics b. Should be used in neutral or reducing atmosphere c. Exhibit high shrinkage on thermal treatment d. Are not resistant to corrosion by slag
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5) Zirconia refractory_________________? a. Does not react with basic slags b. Is produced from baddeleyite c. Cannot be used as an insulator d. Has poor electrical conductivity at high temperature
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6) Carbon refractories have very high __________________? a. Wetting characteristics b. Refractoriness c. Thermal conductivity d. Both B. and C.
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7) An ideal refractory should have high__________________? a. Spalling rate b. Fusion point c. Shrinkage ability d. None of these
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8) Fusion point of an acidic refractory material is________________? a. Increased by the addition of basic oxides b. Reduced by the addition of basic oxides c. Not affected by the addition of basic oxides d. Always more than 2500°C
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9) Segar cones are used for the determination of ____________ of refractories? a. Softening temperature b. Spalling resistance c. Electrical conductivity d. Resistance to slag attack
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10) Porosity is induced in insulating refractories by adding________________? a. Powdered naphthalene b. Ammonium chloride/sulphate c. Calcium phosphate d. All A., B. and C.
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11) Machine moulding of dry mixture of refractories requires a pressure of the order of _____________ kg/cm2? a. 10 b. 100 c. 500 d. 1000
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12) Carbon bricks are not used in the lining of the_________________? a. Combustion chamber of blast furnace stoves b. Electric furnaces c. Highly chemical resistant equipments d. Blast furnace hearth
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13) 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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14) Which of the following does not occur during firing/burning of refractories ? a. Removal of water of hydration b. Vitrification c. Decrease in crushing strength d. Development of stable mineral form
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15) Conversion of silica mineral to Cristobalite is accompanied by reduction in its ____________________? a. Volume b. Specific gravity c. Both A. & B. d. Neither A. nor B.
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16) Magnesite chrome bricks are used in the___________________? a. Roof lining of basic open hearth & other basic furnaces b. Reheating furnaces c. Soaking pits d. All A., B. and C.
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17) 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
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18) Periclase is___________________? a. Crystalline form of MgO b. MgCO3 c. ZrSO4 d. Amorphous magnesite
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19) RUL of refractories depends on the _____________________? a. Chemical composition b. Physical structure c. Presence of impurities like iron & alkali d. All A., B. and C.
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20) Which one contains maximum percentage of Al2O3 ? a. Firebrick b. Sillimanite c. Magnesite d. Aluminous firebrick
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