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  • Question
  • Which of the following has the lowest electrical resistivity?


  • Options
  • A. Graphite
  • B. Fireclay
  • C. Alumina
  • D. Zircon

  • Correct Answer
  • Graphite 


  • Refractory Technology problems


    Search Results


    • 1. Silica refractories are not used in

    • Options
    • A. coke oven walls.
    • B. beehive coke ovens.
    • C. dome and upper portion of B.F. stoves.
    • D. open hearth furnace roof.
    • Discuss
    • 2. Carbon bricks are not used in the lining of the

    • Options
    • A. combustion chamber of blast furnace stoves.
    • B. electric furnaces.
    • C. highly chemical resistant equipments.
    • D. blast furnace hearth.
    • Discuss
    • 3. Pick out the wrong statement.

    • Options
    • A. Sand & coke is the main raw material for the manufacture of silicon carbide.
    • B. Carbon refractories can not be used in the furnaces operating under reducing conditions.
    • C. Mullite can be obtained by the heating of alusite, kyanite or silimanite.
    • D. Silica occurs in nature in all cellular, amorphous or crystalline form.
    • Discuss
    • 4. Silica bricks have low spalling resistance below 600°C, due to its

    • Options
    • A. very high thermal conductivity.
    • B. high co-efficient of expansion upto this temperature.
    • C. high thermal diffusivity.
    • D. low refractoriness.
    • Discuss
    • 5. Which of the following bricks has the most close values of RUL and PCE?

    • Options
    • A. Silica bricks
    • B. Fireclay bricks
    • C. High alumina bricks
    • D. Tar dolomite bricks
    • Discuss
    • 6. Segar cones are used for the determination of __________ of refractories.

    • Options
    • A. softening temperature
    • B. spalling resistance
    • C. electrical conductivity
    • D. resistance to slag attack
    • Discuss
    • 7. Lower part of hot metal mixer are lined with __________ bricks.

    • Options
    • A. superduty fireclay
    • B. high alumina
    • C. silica
    • D. carborundum
    • Discuss
    • 8. Pick out the wrong statement.

    • Options
    • A. Electrical conductivity of refractory is not important, when these are to be used in electrical furnaces.
    • B. Graphite and metals are the good electrical conductor among the refractories and others are all electrical insulators.
    • C. Refractories used for lining electrical furnaces should ordinarily have very low electrical conductivity.
    • D. Electrical conductivity of porous refractory material is low.
    • Discuss
    • 9. Pick out the wrong statement.

    • Options
    • 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.
    • Discuss
    • 10. Refractory materials are never used in the construction of

    • Options
    • A. segar cones
    • B. orton cones
    • C. pressure vessels
    • D. ovens & retorts
    • Discuss


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