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Free download in PDF Engineering Materials Objective Type Questions & Answers for competitive exams. These short objective type questions with answers are very important for Board exams as well as competitive exams. These short solved questions or quizzes are provided by Gkseries.
(21)
A reversible change in the atomic structure of the steel with a corresponding change in the properties is known as
[A]
allotropic change
[B]
recrystallisation
[C]
heat treatment
[D]
precipitation
Answer: allotropic change
(22)
Iron is
[A]
paramagnetic
[B]
ferromagnetic
[C]
ferroelectric
[D]
dielectric
(23)
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 is made by adding suitable percent¬age of carbon to molten iron and subjecting the product to repeated hammering and rolling.
Answer: It is made by adding suitable percent¬age of carbon to molten iron and subjecting the product to repeated hammering and rolling.
(24)
Sulphur in pig iron tends to make it
[A]
hard
[B]
ductile
[C]
tough
[D]
soft
(25)
Wrought iron is
[A]
hard
[B]
high in strength
[C]
highly resistant to corrosion
[D]
heat treated to change its properties
Answer: highly resistant to corrosion
(26)
In malleable iron, carbon is present in the form of
[A]
cementite
[B]
free carbon
[C]
flakes
[D]
nodular aggregates of graphite
Answer: nodular aggregates of graphite
(27)
In nodular iron, graphite is in the form of
[A]
cementite
[B]
free carbon
[C]
flakes
[D]
spheroids
(28)
In grey cast iron, carbon is present in the form of
[A]
cementite
[B]
free carbon
[C]
flakes
[D]
spheroids
(29)
Cast iron is characterised by minimum of following %age of carbon
[A]
2%
[B]
1.3%
[C]
0.8%
[D]
0.2%
(30)
The unique property of cast iron is its high
[A]
malleability
[B]
ductility
[C]
surface finish
[D]
damping characteristics
Answer: damping characteristics
31
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
Answer: product of blast furnace made by reduction of iron ore
32
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%
33
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%
34
For the allotropic forms of iron, the points of arrest are
[A]
the points where no further change oc-curs
[B]
constant for all metals
[C]
the points where there is no further flow of metal
[D]
the points of discontinuity
Answer: the points of discontinuity
35
The metallic structure of mild steel is
[A]
body centred cubic
[B]
face centred cubic
[C]
hexagonal close packed
[D]
cubic structure
Answer: body centred cubic
36
The crystal of alpha iron is
[A]
body centred cubic
[B]
face centred cubic
[C]
hexagonal close packed
[D]
cubic structure
Answer: body centred cubic
37
The crystal structure of gamma iron is
[A]
body centred cubic
[B]
face centred cubic
[C]
hexagonal close packed
[D]
cubic structure
Answer: face centred cubic
38
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
Answer: back and forth like tiny pendulums
39
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
Answer: allotropic change
40
Paramagnetic alpha iron changes to gamma iron at
[A]
770°C
[B]
910°C
[C]
1440°C
[D]
1539°C
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