Practice Test: Question Set - 02
1. Chromite refractories are used in
- (A) Bottom of soaking pits
- (B) Between acid & basic linings in basic open hearth furnaces to
prevent their chemical action with each other
- (C) Both (a) & (b)
- (D) Neither (a) nor (b)
2. The linear thermal expansion of __________ bricks upto 1000 °C is very low of the order of ≤ 0.5 percent.
- (A) Fireclay
- (B) Silica
- (C) Magnesite
- (D) Corundum
3. Maximum apparent porosity of magnesite bricks is about __________ percent.
- (A) 8
- (B) 24
- (C) 44
- (D) 58
4. Chrome magnesite is not used in the
- (A) Inner lining of L.D. converter
- (B) Aluminium melting furnaces
- (C) Wear out lining of steel melting furnaces
- (D) All (a), (b) and (c)
5. Cold crushing strength of refractories depends upon its
- (A) Composition
- (B) Texture
- (C) Firing temperature
- (D) All (a), (b) and (c)
6. ________ bricks are used in the burning zone of a cement rotary kiln.
- (A) High alumina
- (B) Fireclay
- (C) Thoria
- (D) Silicon carbide
7. Pick out the wrong statement.
- (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
8. Maximum water percentage in refractory mix meant for hand moulding may be as high as __________ percent.
- (A) 2-3
- (B) 5-7
- (C) 7-12
- (D) 14-20
9. Which property is important for bricks used in the combustion chamber & dome of blast furnace stoves?
- (A) High refractoriness
- (B) High resistance to spalling
- (C) High strength and density
- (D) All (a), (b) and (c)
10. Which of the following has the lowest electrical resistivity?
- (A) Graphite
- (B) Fireclay
- (C) Alumina
- (D) Zircon
11. Spalling resistance of a refractory cannot be increased by
- (A) Increasing its porosity
- (B) Using a coarser grog during its manufacture
- (C) Decreasing its thermal co-efficient of expansion
- (D) Making it denser
12. Refractory castables are used for
- (A) Producing monolithic linings
- (B) Patch work
- (C) Minimising the number of joints in the structure
- (D) All (a), (b) and (c)
13. 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
14. Silicon carbide refractories have very low
- (A) Refractoriness (< 1700°C)
- (B) Thermal conductivity
- (C) Resistance to thermal shock
- (D) None of these
15. 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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