In spheroidising process, the steel is
Heated below the lower critical temperature and then cooled slowly
Heated up to the lower critical temperature and then cooled in still air
Heated slightly above the lower critical temperature and then cooled slowly to a temperature of 600°C
None of the above
Correct Answer :
C. Heated slightly above the lower critical temperature and then cooled slowly to a temperature of 600°C
Related Questions
Maximum percentage of carbon in ferrite is
0.025 %
0.06 %
0.1 %
0.25 %
The most effective inhibitor of grain growth, when added in small quantities is
Carbon
Vanadium
Manganese
Cobalt
The correct composition of Babbitt metal is
87.75% Sn, 4% Cu, 8% Sb, 0.25% Bi
90% Sn, 2% Cu, 4% Sb, 2% Bi, 2% Mg
87% Sn, 4% Cu, 8% Sb, 1% Al
82% Sn, 4% Cu, 8% Sb, 3% Al, 3% Mg
The alloying element which increases residual magnetism and coercive magnetic force in steel for magnets is
Chromium
Nickel
Vanadium
Cobalt
The portion of the blast furnace below its widest cross-section is called
Hearth
Stack
Bosh
Throat
Which of the following iron exist between 910°C and 1403°C?
α-iron
β-iron
γ-iron
δ-iron
High carbon steel carries carbon percentage
0.1 to 0.3 %
0.3 to 0.6 %
0.6 to 0.8 %
0.8 to 1.5 %
The molecules in a solid move
In a random manner
In a haphazard way
In circular motion
Back and forth like tiny pendulums
Iron is
Paramagnetic
Ferromagnetic
Ferroelectric
Dielectric
The material in which the atoms are arranged regularly in some directions but not in others, is called
Amorphous material
Mesomorphous material
Crystalline material
None of these
Constantan an alloy used in thermocouples is an alloy of
Copper and tin
Copper and zinc
Copper and iron
Copper and nickel
Which of the following metal shrinks most from molten state to solid state?
Cast iron
Cast steel
Brass
Admiralty metal
Brass contains
70% copper and 30% zinc
90% copper and 10% tin
85 - 92% copper and rest tin with little lead and nickel
70 - 75% copper and rest tin
The compressive strength of cast iron is ________ that of its tensile strength.
Equal to
Less than
More than
None of these
Vanadium in high speed steels
Promotes decarburisation
Provides high hot hardness
Forms very hard carbides and thus increases wear resistance
Promotes retention of austenite
Pick up wrong statement about wrought iron
It contains carbon of the order of 0 to 0.25%
It melts at 1535°C
It is very soft and ductile
It is made by adding suitable percentage of carbon to molten iron and subjecting the product to repeated hammering and rolling.
Body centered cubic space lattice is found in
Zinc, magnesium, cobalt, cadmium, antimony and bismuth
Gamma iron, aluminium, copper, lead, silver and nickel
Alpha iron, tungsten, chromium and molybdenum
None of the above
Ductile cast iron
Contains 1.7 to 3.5% carbon in Free State and is obtained by the slow cooling of molten cast iron
Is also known as chilled cast iron and is obtained by cooling rapidly. It is almost unmachinable
Is produced by annealing process. It is soft, tough and easily machined metal
Is produced by small additions of magnesium (or creium) in the ladle. Graphite is in nodular or spheroidal form and is well dispersed throughout the material
By severely deforming a metal in a particular direction it becomes
Ductile
Malleable
Homogeneous
Anisotropic
A material is known as allotropic or polymorphic if it
Has a fixed structure under all conditions
Exists in several crystal forms at different temperatures
Responds to heat treatment
Has its atoms distributed in a random pattern
When filing or machining cast iron makes our hands black, then it shows that ________ is present in cast iron.
Cementite
Free graphite
Both A and B
None of these
Tungsten when added to steel ________ the critical temperature.
Does not effect
Lowers
Raises
None of these
Lead is poured into the joint between two pipes. These pipes may be made of
Cast iron
Vitrified clay
Asbestos cement
Concrete
Pick up the wrong statement
Aluminium in steel results in excessive grain growth
Manganese in steel induces hardness
Nickel and chromium in steel helps in raising the elastic limit and improve the resilience and ductility
Tungsten in steels improves magnetic properties and hardenability
Which of the following metal is used for nuclear energy?
Uranium
Thorium
Niobium
All of these
In high speed steels, manganese is used to tougher the metal and to increase its
Yield point
Critical temperature
Melting point
Hardness
For the allotropic forms of iron, the points of arrest are
The points where no further change occurs
Constant for all metals
The points where there is no further flow of metal
The points of discontinuity
Which of the following alloys does not contain tin?
White metal
Solder admiralty
Fusible metal
Phosphor bronze
White cast iron has
Carbon in the form of carbide
Low tensile strength
High compressive strength
All of these
In a hardening process, the hypo-eutectoid steel is
Heated from 30°C to 50°C above the upper critical temperature and then cooled in still air
Heated from 30°C to 50°C above the upper critical temperature and then cooled suddenly in a suitable cooling medium
Heated from 30°C to 50°C above the upper critical temperature and then cooled slowly in the furnace
Heated below or closes to the lower critical temperature and then cooled slowly