1) High refractoriness of refractory bricks means, that it has a________________? a. High spalling resistance b. Low spalling resistance c. High resistance to fusion d. Low porosity
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2) 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.
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3) Cermets are____________________? a. Composite material containing both ceramic & metallic constituents b. Having high strength & resistance to high temperature c. Used in space vehicles, missiles & nuclear energy plants d. All A., B. and C.
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4) Dry mix hydraulic compositions of refractory aggregates with suitable bonding materials are called refractory_________________? a. Mortars b. Cements c. Castables d. None of these
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5) 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.
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6) Periclase refractory contains mainly________________? a. CaO b. MgO c. Al2O3 d. SiO2
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7) Silica bricks have low spalling resistance below 600°C, due to its________________? a. Very high thermal conductivity b. High co-efficient of expansion upto this temperature c. High thermal diffusivity d. Low refractoriness
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8) Magnesite refractories have low resistance to___________________? a. Attack by basic slag b. Abrasion c. Disintegration on sudden change of temperature d. Both B. and C.
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9) Which is a basic refractory ? a. Fireclay b. Silica c. Chrome magnesite d. None of these
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10) Tar dolomite bricks are used in the_________________? a. Basic Bessemer converter b. Basic open hearth furnace c. Electric furnaces d. All A., B. and C.
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11) Cold crushing strength of fireclay bricks is about ______________ kgf/cm2? a. 50-100 b. 100-150 c. 200-400 d. 500-1000
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12) Sillimanite (Al2O3.SiO2) refractory, which is a neutral refractory, is not used in________________? a. Pottery furnace b. Glass melting furnace c. Crucibles d. Gas retorts
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13) 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
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14) Tar bonded dolomite bricks__________________? a. Are stored under controlled temperature & humidity to avoid hydration b. Are used in outer lining of L.D. converters c. Have poorer hydration resistance than pitch bonded bricks d. All A., B. and C.
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15) Which furnace consumes maximum refractory annually in an integrated steel plant ? a. Soaking pit b. Blast furnace c. L.D. converter d. Coke ovens
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16) Which of the following bricks should not be used, if the furnace is to be used intermittently ? a. Firebricks b. Silica bricks c. Silicon carbide bricks d. Sillimanite
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17) Refractoriness under load (RUL) is the most important property for the refractory bricks_________________? a. At the hearth bottom of the furnace on which stock is placed b. Used for furnace insulation c. Used in the roof of the furnace d. None of these
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18) Ganister is a source of the ________________? a. Silica b. Periclase c. Lime d. None of these
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19) Which is required in an insulating refractory ? a. High thermal conductivity b. Low porosity c. Both A. and B. d. Neither A. nor B.
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20) Sillimanite is a _____________ refractory? a. Basic b. Neutral c. High alumina d. Insulating
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