26. A reversible change in the atomic structure of steel with corresponding change in the properties is known as
(a) molecular change
(b) physical change
(c) allotropic change
(d) solidus change
(e) atomic change.
Ans: c
27. The molecules in a solid move
(a) in a random manner
(b) in a haphazard way
(c) in circular motion
(d) back and forth like tiny pendulums
(e) do not move.
Ans: d
28. The crystal structure of gamma iron is
(a) body centred cubic
(b) face centred cubic
(c) hexagonal close packed
(d) cubic structure
(e) orthorhombic crystal.
Ans: b
29. The crystal of alpha iron is
(a) body centred cubic
(b) face centred cubic
(c) hexagonal close packed
(d) cubic structure
(e) orthorhombic crystal.
Ans: a
30. The metallic structure of mild steel is
(a) body centred cubic
(b) face centred cubic
(c) hexagonal close packed
(d) cubic structure
(e) orthorhombic crystal.
Ans: a
31. For the allotropic forms of iron, the points of arrest are
(a) the points where no further change occurs
(b) constant for all metals
(c) the points where there is no further flow of metal
(d) the points of discontinuity
(e) the points where major changes take place.
Ans: d
32. The percentage of carbon in pig iron varies from
(a) 0.1 to 1.2%
(b) 1.5 to 2.5%
(c) 2.5 to 4%
(d) 4 to 4.5%
(e) 4.5 to 6.3%.
Ans: d
33. The percentage of carbon in grey iron castings usually varies between
(a) 0.5 to 1%
(b) 1 – 2%
(c) 2.5 to 4.5%
(d) 5 – 7%
(e) 7-9%.
Ans: c
34. Pig iron is the name given to
(a) raw material for blast furnace
(b) product of blast furnace made by reduction of iron ore
(c) iron containing huge quantities of carbon
(d) iron in molten form in the ladles
(e) iron scrap.
Ans: b
35. The unique property of cast iron is its high
(a) malleability
(b) ductility
(c) surface finish
(d) damping characteristics
(e) hardness.
Ans: d
36. Cast iron is characterised by minimum of following %age of carbon
(a) 0.2%
(b) 0.8%
(c) 1.3%
(d) 2%
(e) 6.3%.
Ans: d
37. In grey cast iron, carbon is present in the form of
(a) cementite
(b) free carbon
(c) flakes
(d) spheroids
(e) nodular aggregates of graphite.
Ans: c
38. In nodular iron, graphite is in the form of
(a) cementite
(b) free carbon
(C) flakes
(d) spheroids
(e) nodular aggregates of graphite.
Ans: d
39. In malleable iron, carbon is present in the form of
(a) cementite
(b) free carbon
(c) flakes
(d) spheroids
(e) nodular aggregates of graphite.
Ans: e
40. Wrought iron is
(a) hard
(b) high in strength
(c) highly resistant to corrosion
(d) heat treated to change its properties
(e) least resistant to corrosion.
Ans: c
41. Sulfur in pig iron tends to make it
(a) hard’
(b) soft
(c) ductile
(d) tough
(e) malleable.
Ans: a
42. Pick up wrong statement about wrought iron
(a) It contains carbon of the order of 0 to 0.25%
(b) It melts at 1535°C
(c) It is very soft and ductile
(d) It can be easily forge welded
(e) It is made by adding suitable percent¬age of carbon to molten iron and subjecting the product to repeated hammering and rolling.
Ans: e
43. Iron is
(a) paramagnetic
(b) ferromagnetic
(c) ferroelectric
(d) dielectric
(e) none of the above.
Ans: b
44. A reversible change in the atomic structure of the steel with a corresponding change in the properties is known as
(a) allotropic change
(b) recrystallization
(c) heat treatment
(d) precipitation
(e) austempering.
Ans: a
45. Chilled cast iron has
(a) no graphite
(b) a very high percentage of graphite
(c) a low percentage of graphite
(d) graphite as its basic constituent of composition
(e) none of the above is true.
Ans: a
46. Cast iron has
(a) high tensile strength
(b) its elastic limit close to the ultimate breaking strength
(c) high ductility
(d) all of the above
(e) none of the above.
Ans: b
47. White cast iron contains carbon in the form of
(a) free carbon
(b) graphite
(c) cementite
(d) white carbon
(e) ferrite.
Ans: c
48. In mottled cast iron, carbon is available in
(a) free form
(b) combined form
(c) nodular form
(d) flat form
(e) partly in free and partly in combined state.
Ans: e
49. An important property of high silicon (12 – 18%) cast iron is the high
(a) tenacity
(b) brittleness
(c) plasticity
(d) corrosion resistance
(e) hardness.
Ans: e
50. An important property of malleable cast iron in comparison to grey cast iron is the high
(a) compressive strength
(b) ductility
(c) carbon content
(d) hardness
(e) surface finish.
Ans: b