Multiple Choice Questions and Answers on Refractory Technology
01. Silica refractories are not used in
(A) Coke oven walls
(B) Beehive coke ovens
(C) Dome and upper portion of B.F. stoves
(D) Open hearth furnace roof
Answer: Option B
02. Si percentage in silica refractories used in the walls of coke oven is about
(A) 45
(B) 60
(C) 80
(D) 95
Answer: Option D
03. Porosity of silica bricks varies from __________ percent.
(A) 5 to 10
(B) 20 to 30
(C) 45 to 60
(D) 60 to 75
Answer: Option B
04. Chrome magnesite bricks are
(A) Acidic in nature
(B) Neutral in nature
(C) Having higher RUL than silica bricks
(D) Made by mixing 30% Chromite and 70% Periclase
Answer: Option C
05. Alumina-graphite bricks are used for lining the
(A) Slide gate in teeming laddies
(B) Continuous casting systems
(C) Both (A) and (B)
(D) Neither (A) nor (B)
Answer: Option C
06. Maximum shrinkage in volume occurring during burning/firing of dried refractories may be as high as __________ percent.
(A) 10
(B) 15
(C) 20
(D) 30
Answer: Option D
07. The main raw material for manufacture of silicon carbide refractories is
(A) Corundum
(B) Carborundum
(C) Bauxite
(D) Periclase
Answer: Option B
08. Which of the following consumes the maximum tonnage of refractories annually in an integrated steel plant?
(A) Soaking pits
(B) Reheating furnace
(C) L.D. converter
(D) Rotary lime kiln
Answer: Option C
09. Upper portion of hot metal mixer are lined with mullite bricks, which helps in resisting the
(A) Washing action of metal
(B) Corrosion by layer of slag
(C) Both (A) & (B)
(D) Neither (A) nor (B)
Answer: Option A
10. Lower part of hot metal mixer are lined with __________ bricks.
(A) Superduty fireclay
(B) High alumina
(C) Silica
(D) Carborundum
Answer: Option D
11. High density refractory bricks have lower
(A) Spalling resistance
(B) Thermal conductivity
(C) Fusion point
(D) Slag penetration resistance
Answer: Option A
12. Bauxite calcining rotary kilns are lined with __________ bricks.
(A) Fireclay
(B) Carbon
(C) 85% alumina
(D) Corundum
Answer: Option C
13. Fireclay bricks are used in the
(A) Furnaces allowed to cool frequently
(B) Flues
(C) Chimney linings
(D) All (A), (B) and (C)
Answer: Option D
14. Carbon refractory blocks
(A) Are wetted by molten iron
(B) Are used in the hearth of blast furnace
(C) Are acidic in nature
(D) All (A), (B) and (C)
Answer: Option B
15. Spalling of a refractory means its
(A) Softening
(B) Fracture due to uneven expansion at high temperature
(C) Resistance to compressive loads
(D) Resistance to chemical action of gases and molten fluxes
Answer: Option B
16. 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) and (B)
Answer: Option C
17. 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
Answer: Option A
18. Maximum apparent porosity of magnesite bricks is about __________ percent.
(A) 8
(B) 24
(C) 44
(D) 58
Answer: Option B
19. 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), and (B) and (C)
Answer: Option C
20. Cold crushing strength of refractories depends upon its
(A) Composition
(B) Texture
(C) Firing temperature
(D) All (A), (B) and (C)
Answer: Option D
21. __________ bricks are used in the burning zone of a cement rotary kiln.
(A) High alumina
(B) Fireclay
(C) Thoria
(D) Silicon carbide
Answer: Option A
22. 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
Answer: Option D
23. 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
Answer: Option D
24. 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)
Answer: Option A
25. Which of the following has the lowest electrical resistivity?
(A) Graphite
(B) Fireclay
(C) Alumina
(D) Zircon
Answer: Option A