Refractory Technology MCQs

Question 1

Which refractory must have controlled atmosphere (temperature and humidity) for its safe storage?

Accepted Answer

Tar bonded dolomite bricks

Answer

Fireclay bricks

Answer

Mullite bricks

Answer

Magnesite bricks

Question 2

What is Thoria?

Accepted Answer

All of the above

Answer

Thoria Has high fusion temperature (> 3000°C) but poor resistance to thermal shock

Answer

Thoria Has high resistance to basic slags

Answer

Which is expensive & radioactive, is used in crucibles for melting high purity metals

Question 3

To resist spalling tendency, a refractory should have

Accepted Answer

All of the above

Answer

Greater diffusivity

Answer

Low specific heat

Answer

Low thermal co-efficient of expansion

Question 4

Chrome magnesite brick is not used for lining the

Accepted Answer

Coke oven regenerator

Answer

Hearth of soaking pits

Answer

Bottom hearth of reheating furnace

Answer

Burning zone of limestone rotary kilns

Question 5

Faster rate of drying of moulded refractories results in high __________ of refractories.

Accepted Answer

Both B and C

Answer

Green strength

Answer

Voids

Answer

Shrinkage

Question 6

SiO 2 percentage in firebrick is about

Accepted Answer

55 - 60

Answer

35 - 40

Answer

80 - 85

Answer

> 94

Question 7

Which brick undergoes maximum shrinkage on drying?

Accepted Answer

Fireclay bricks

Answer

Tar bonded dolomite bricks

Answer

Magnesite bricks

Answer

Chromite bricks

Question 8

Natural silica

Accepted Answer

All of the above

Answer

Mainly contains quartz

Answer

Is not stable at high temperature

Answer

Transforms to other allotropic forms i.e tridymite and cristoballite involving very high volume changes

Question 9

Resistance to slag attack of a refractory

Accepted Answer

All of the above

Answer

Depends on the nature of slag & refractory

Answer

Decreases at higher temperature

Answer

Decreases, if defective joints & cracks exist in the refractory