Questions and answers for exam Preparation

MCQs

Total Questions : 868 | Page 81 of 87 pages

Question 801. Addition of grog in fireclay brick during its manufacture is advantageous, because it results in_____________________?

Less shrinkage in heating, decreased apparent porosity & increased specific gravity
High strength & thermal spalling resistance
Less addition of water to get a workable plasticity & lesser time required for drying the raw refractories and hence increased rate of production
All A., B. and C.

Discuss Question

Answer: Option D. -> All A., B. and C.
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!

Question 802. Skull is not formed on the carbon blocks in the hearth of a blast furnace, when it becomes cold, because of its_______________?

Discuss Question

Answer: Option A. -> Non-wetting characteristic
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!

Question 803. ‘Super refractories’ are made from pure____________________?

Discuss Question

Answer: Option B. -> Oxides
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!

Question 804. Use of higher percentage of lime for bonding silica bricks, reduces their__________________?

Discuss Question

Answer: Option C. -> Both A. & B.
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!

Question 805. Magnesite chrome refractories____________________?

Have better spalling resistance than chrome magnesite refractories
Have very low thermal co-efficient of expansion
Are not at all resistant to the corrosive action of iron oxide
Have very low (50 kg/cm2) cold crushing strength (C.C.S.), and cannot be used in metalcase form

Discuss Question

Answer: Option A. -> Have better spalling resistance than chrome magnesite refractories
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!

Question 806. Chromite refractories are_____________________?

Discuss Question

Answer: Option B. -> Neutral refractory
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!

Question 807. Maximum safe working temperature for fireclay bricks is about __________ °C?

Discuss Question

Answer: Option D. -> 1550
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!

Question 808. Cold crushing strength of a refractory does not depend upon its ____________________?

Discuss Question

Answer: Option A. -> Shape
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!

Question 809. Thoria__________________?

Has high fusion temperature (> 3000°C) but poor resistance to thermal shock
Has high resistance to basic slags
Which is expensive & radioactive, is used in crucibles for melting high purity metals
All A., B. and C.

Discuss Question

Answer: Option D. -> All A., B. and C.
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!

Question 810. Which is the stable form of silica between 1470°C and the melting point 1713°C ?