MCQ
621. Gamma iron exits at following temperature--.
room temperature
between 1400°C and 1539°C
near melting point
between 910°C and 1400°C
622. The molecules in a solid move—
in a random manner
in a haphazard way
in circular motion
back and forth like tiny pendulums
623. Chilled cast iron has--
no graphite
a very high percentage of graphite
a low percentage of graphite
graphite as its basic constituent of composition
624. The unique property of cast iron is its high--
malleability
ductility
surface finish
damping characteristics
625. A reversible change in the atomic structure of the steel with a corresponding change in the properties is known as--
allotropic change
heat treatment
recrystallisation
precipitation
626. Pick up the wrong statement –
aluminium in steel results in excessive grain growth
manganese in steel induces hardness
nickel and chromiam in steel help in raising the elastic limit and improve the resilience and ductility
tungsten in steels improves magnetic properties and hardenability
627. Pure iron is the structure of--.
ferrite
anstenite
ferrite and cementite
pearlite
628. A reversible change in the atomic structure of steel with corresponding change in the properties is known as—
molecular change
physical change
allotropic change
solidus change
629. Amorphous material is one--
in which atoms align themselves in a geometric pattern upon solidification
in which there is no definite atomic structure and atoms exist in a random pattern just as in a liquid
which is not attacked by phosphorous
which is not attacked by phosphorous
630. 'Killed steels are those steels—
which are destroyed by burning
which after their destruction are recycled to produce fresh steel
which are deoxidised in the ladle with silicon and aluminium
in which carbon is compictely burnt
631. Railway rails are normally made of –
mild steel
alloy steel
high carbon
tungsten steel
632. Ferromagnetic alpha iron exists in temperature range of--
below 723°C
770-910°C
910-1440°C
1400-1539°C
633. Which of the following iron exists 910°C?
∝-iron
δ -iron
β-iron
γ-iron
634. Carbon steel is--
made by adding carbon in steel
refined from cast iron
an alloy of iron and carbon with varying quantities of phosphorus and sulphur
extensively used for making cutting tools
635. The temperature at which ferromagnetic alpha iron transforms to paramagnetic alpha iron is-
770°C
910°C
1050°C
below recrystallisation temperature
636. The material mixed before ore is subjected for smelting in the extraction of iron are-
Coke and Silica
Coke and limestone
Limestone and silica
Coke, limestone and silica
637. Paramagnetic alpha iron changes to gamma iron at--
770°C
910°C
1440°C
1539°C
638. The crystal structure of gamma iron is—
body centred cubic
face centred cubic
hexagonal close packed
cubic structure
639. The following types of materials are usually the most ductile--
face-centred cubic lattice
body-centred cubic lattice
hexagonal close-packed lattice
all of the above
640. Iron-carbon alloys containing carbon........... 4.3% are known as hyper eutectic cast irons--
equal to
leas than
more than
none