E-PolyLearning

11. Machinability of hard alloys and tool steels is improved by
a. spherodising
b. annealing
c. tempering
d. normalising
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Answer: (b).annealing

12. Transformation range for ferrous material is the temperature interval during which __________ is formed during its heating.
a. cementite
b. austenite
c. martensite
d. pearlite
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Answer: (b).austenite

13. Powder metallurgy process does not make metal powder by
a. atomisation
b. grinding/milling
c. hammering
d. electrolytic deposition
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Answer: (c).hammering

14. In the blast furnace, incorporation of water vapour in the blast gives the following effect.
a. Increases the reducing potential of the gas.
b. Increases the flame temperature.
c. No significant change occurs.
d. Increases the hydrogen content in the metal.
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Answer: (a).Increases the reducing potential of the gas.

15. Pick out the wrong statement.
a. A ferromagnetic material becomes paramagnetic above the 'Curie temperature'.
b. Permanent magnets are made of hard materials, whereas electromagnets require soft magnetic materials.
c. Soft magnetic materials (e.g., pure iron) have higher permeability and low hysterisis loss and coercive forces.
d. Tungsten steel and alnico are not hard magnetic materials.
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Answer: (d).Tungsten steel and alnico are not hard magnetic materials.

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