This set of Iron Making Multiple Choice Questions & Answers (MCQs) focuses on “Blast Furnace Slag Composition and Viscosity”.
1. The major constituents of blast furnace slag is ____________
a) CaO, Al2O3, SiO2
b) Al2O3, SiO2
c) CaO, Al2O3
d) CaO, SiO2
View Answer
Explanation: CaO comes from limestone into the slag. While Al2O3 & SiO2 come from the gangue into the slag. Some amount of MgO also came into the slag from the flux. A small amount of TiO2, FeO, alkali oxides are also present.
2. Liquid slag viscosity is very much higher than liquid iron.
a) True
b) False
View Answer
Explanation: Liquid slag viscosity is very much higher than liquid iron. The viscosity varies drastically depending on the composition and temperature. The value of viscosity of slag ranges from 2.5 to 2000 poise.
3. The viscosity of liquid slag is lower than __________ inside the blast furnace.
a) 3 poise
b) 2 poise
c) 1 poise
d) 4 poise
View Answer
Explanation: Viscosity of liquid slag is lower than 2 poise. It helps in the proper functioning of the blast furnace. High viscous slag poses difficulties during slag–metal separation in the hearth, slowdown the rates of slag-metal reactions, etc.
4. The V-Ratio of the Hearth slag is maintained between 1.0 and 1.25.
a) True
b) False
View Answer
Explanation: V ratio = wt.%CaO / wt.%SiO in slag. Basic slag facilitates the transfer of both sulphur and silicon from the metal to slag but it also has higher viscosity. Low viscosity along with good transferability of elements favors the proper functioning of the blast furnace. The V-Ratio of the Hearth slag in the range of 1.0 and 1.25 fulfill these two contradictory requirements.
5. The melting point of FeO–SiO2 compounds is ___________
a) 1200-1300°C
b) 1300-1400°C
c) 1400-1500°C
d) 1500-1600°C
View Answer
Explanation: Melting point of FeO–SiO2 compounds is 1200-1300°C. Melting of iron ore is possible at such lower temperature only when the formation of FeO–SiO2 compound takes place in large amount.
6. MgO in the slag is _________
a) 4-10%
b) 5-10%
c) 2-6%
d) 1-5%
View Answer
Explanation: Slags containing 4–10% MgO is used in the blast furnace. MgO lowers both the liquidus temperature as well as the viscosity. Nowadays it has been a normal practice to keep the MnO in this proportion.
7. Slag viscosity decreases as temperature _______
a) Increases
b) Decreases
c) Remains constant
d) Decreases rapidly
View Answer
Explanation: The viscosity decreases with the increasing temperature. Fluid, free-running slag obtains at the minimum hearth temperature. This temperature is known as the Critical Hearth Temperature. It should be as low as possible for proper functioning of blast furnace.
Sanfoundry Global Education & Learning Series – Iron Making.
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