Hardness of martensite is about
RC 65
RC 48
RC 57
RC 80
Correct Answer :
A. RC 65
Related Questions
The bond formed by transferring electrons from one atom to another is called
Ionic bond
Covalent bond
Metallic bond
None of these
Which of the following constituents of steels is softest and least strong?
Austenite
Pearlite
Ferrite
Cementite
Basic constituents of Monel metal are
Nickel, copper
Nickel, molybdenum
Zinc, tin, lead
Nickel, lead and tin
Chromium in steel
Improves wear resistance, cutting ability and toughness
Refines grain size and produces less tendency to carburisation, improves corrosion and heat resistant properties
Improves cutting ability and reduces hardenability
Gives ductility, toughness, tensile strength and anticorrosion properties
Cast iron is a
Ductile material
Malleable material
Brittle material
Tough material
The following element can't impart high strength at elevated temperature
Manganese
Magnesium
Nickel
Silicon
According to Indian standard specifications, plain carbon steel designated by 40 C8 means that the carbon content is
0.04 %
0.35 to 0.45 %
0.4 to 0.6 %
0.6 to 0.8 %
Isotropic materials are those which have the same
Elastic properties in all directions
Stresses induced in all directions
Thermal properties in all directions
Electric and magnetic properties in all directions
The unique property of cast iron is its high
Malleability
Ductility
Surface finish
Damping characteristics
The surface hardness of the following order is achieved by nitriding operation
600 VPN
1500 VPN
1000 to 1100 VPN
250 VPN
A specimen of aluminium metal when observed under microscope shows
B.C.C. crystalline structure
F.C.C. crystal structure
H.C.P. structure
A complex cubic structure
'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 completely burnt
Neutral solution is one which has pH value
Greater than 7
Less than 7
Equal to 7
pH value has nothing to do with neutral solution
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
According to Indian standard specifications, SG 400/15 means
Spheroidal graphite cast iron with B.H.N. 400 and minimum tensile strength 15 MPa
Spheroidal graphite cast iron with minimum tensile strength 400 MPa and 15 percent elongation
Spheroidal graphite cast iron with minimum compressive strength 400 MPa and 15 percent reduction in area
None of the above
For a steel containing 0.8% carbon
There is no critical point
There is only one critical point
There are two critical points
There can be any number of critical points
Wrought iron is
Hard
High in strength
Highly resistant to corrosion
Heat treated to change its properties
The ability of a material to resist softening at high temperature is known as
Creep
Hot tempering
Hot hardness
Fatigue
Eutectoid reaction occurs at
600°C
723°C
1147°C
1493°C
The coke in the charge of blast furnace
Controls the grade of pig iron
Acts as an iron bearing mineral
Supplies heat to reduce ore and melt the iron
Forms a slag by combining with impurities
Maximum percentage of carbon in austenite is
0.025 %
0.26 %
0.8 %
1.7 %
Free cutting steels
Are used where ease in machining is the criterion
Contain carbon in free form
Require least cutting force
Do not exist
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
Cemented carbide tools are not found to be suitable for cutting
Brass
Cast iron
Aluminium
Steel
Malleable cast iron is produced
By adding magnesium to molten cast iron
By quick cooling of molten cast iron
From white cast iron by annealing process
None of these
Cupola produces following material
Cast iron
Pig iron
Wrought iron
Malleable iron
Macrostructure of a material is, generally, examined by
Naked eye
Optical microscope
Metallurgical microscope
X-ray techniques
Points of arrest for iron correspond to
Stages at which allotropic forms change
Stages at which further heating does not increase temperature for some time
Stages at which properties do not change with increase in temperature
There is nothing like points of arrest
Which of the following metal is used in making electrical resistance wire for electric furnaces and heating elements?
Babbitt metal
Monel metal
Nichrome
Phosphor bronze
Age hardening is related to
Duralumin
Brass
Copper
Silver