Refractory Technology MCQs

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1.Identify the incorrect statement about ceramic materials:

A ceramic substance that melts and can be shaped in its molten or viscous form is called glass.Ceramics do not experience vitrification when heated.Ceramic materials typically exhibit brittleness.Non-oxide ceramics usually behave as semiconductors.

2.Identify the incorrect statement from the options below:

Lime is used as a flux in clay to lower the temperature at which vitrification occurs.The primary components of clay are silica and alumina.Incorporating sand into ceramic materials makes them non-plastic, raises their melting point, and decreases shrinkage during firing.The purpose of vitrifying fireclay is to enhance its porosity.

3.Identify the incorrect statement regarding the electrical conductivity of refractory materials.

The electrical conductivity of refractory materials is irrelevant when they are utilized in electrical applications.Among refractories, graphite and metals exhibit good electrical conductivity, whereas others act as insulators.Refractories employed for lining electrical furnaces typically possess very low electrical conductivity.Porous refractory materials generally have low electrical conductivity.

4.Identify the incorrect statement from the following options:

Silicon carbide is primarily produced using sand and coke as raw materials.Carbon-based refractories are unsuitable for use in furnaces that operate under reducing atmospheres.Mullite can be formed by heating minerals such as alunite, kyanite, or sillimanite.Silica naturally exists in cellular, amorphous, and crystalline forms.

5.Identify the incorrect statement from the following options:

Refractories in a muffle furnace must possess high thermal conductivity.The electrical resistivity of refractories decreases sharply as temperature increases.To minimize spalling, refractories should be properly fired and have higher porosity.The refractoriness under load (RUL) of a refractory material is always lower than its refractoriness.

6.Identify the incorrect statement from the options below:

Insulating refractories that replace standard refractory bricks are commonly referred to as lightweight refractories.Graphite-based refractories are also known by the name plumbago refractories.Superduty fireclay bricks match a pyrometric cone equivalent range of 26 to 28.Dead burnt magnesite is another term for calcined magnesite.

7.What is the chemical composition of carborundum, which is utilized in the production of crucibles for melting non-ferrous metals?

8.What does the permeability of bricks indicate?

Resistance to high temperaturesTemperature at which the brick meltsSpeed at which liquid flows through the brick's poresDegree of expansion when heated

9.In which of the following applications are fireclay bricks typically not utilized?

Blast furnace liningHot blast stove constructionCupola furnace wallsWalls of a coke oven

10.Among the different forms of silica, which one exhibits the greatest specific gravity?

QuartzCristobaliteTridymiteThey all possess identical specific gravity

11.How does the thermal conductivity of refractory bricks change with their porosity?

It rises as the porosity decreasesIt falls when porosity is reducedIt remains unaffected by porosity and is highest in insulating bricksIt goes up with an increase in air trapped within the pores

12.How does the fusion temperature of a basic refractory material change when acid oxides are added?

It decreases due to the incorporation of acid oxidesIt rises as a result of adding acid oxidesIt remains unchanged despite the addition of acid oxidesIt is consistently below 1000°C

13.In which part of industrial equipment are fireclay bricks commonly utilized?

Regenerator of coke ovensExternal lining of the L.D. converterBottom hearth of a blast furnaceWalls of coke ovens

14.Which of the following is not classified as an acidic refractory material?

SilicaFireclayHigh alumina refractoryCarbon black

15.Which of the following is classified as an acidic refractory material?

MagnesiteDolomiteFireclayChrome magnesite

16.During the panel test for evaluating spalling resistance, what is the average surface temperature of the panel assembly held at for a duration of 24 hours?