A small percentage of boron is added to steel in order to
Increase hardenability
Reduce machinability
Increase wear resistance
Increase endurance strength
Correct Answer :
A. Increase hardenability
Related Questions
Railway rails are normally made of
Mild steel
Alloy steel
High carbon
Tungsten steel
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
Chilled cast iron has
No graphite
A very high percentage of graphite
A low percentage of graphite
Graphite as its basic constituent of composition
Bell metal contains
70% copper and 30% zinc
90% copper and 10% ti
85 - 92% copper and rest tin with little lead and nickel
70 - 75% copper and rest tin
Malleability of a material can be defined as
Ability to undergo large permanent deformations in compression
Ability to recover its original form
Ability to undergo large permanent deformations in tension
All of the above
The percentage carbon content in wrought iron is about
0.02
0.1
02
0.4
The transistor is made of
Silver
Gold
Copper
Germanium
Which of the following statement is true about brittle fracture?
High temperature and low strain rates favour brittle fracture
Many metals with hexagonal close packed (H.C.P) crystal structure commonly show brittle fracture
Brittle fracture is always preceded by noise
Cup and cone formation is characteristic for brittle materials
The temperature at which ferromagnetic alpha iron transforms to paramagnetic alpha iron is
770°C
910°C
1050°C
Below recrystallisation temperature
Gamma iron exits at following temperature
Room temperature
Near melting point
Between 1400°C and 1539°C
Between 910°C and 1400°C
The ability of a material to resist softening at high temperature is known as
Creep
Hot tempering
Hot hardness
Fatigue
There are fourteen atoms in a unit cell of
Body centred cubic space lattice
Face centred cubic space lattice
Close packed hexagonal space lattice
None of these
The crystal structure of brass is
F.C.C.
B.C.C.
H.C.P.
Orthorhombic crystalline structure
Inconel is an alloy of
Nickel, chromium and iron
Nickel, copper
Nickel, Chromium
Nickel, zinc
Quenching is not necessary when hardening is done by
Case hardening
Flame hardening
Nitriding
Any one of these
Aluminium bronze contains aluminium and copper in the ratio of
50 : 50
40 : 60
60 : 40
10 : 90
Which of the following represents the allotropic forms of iron?
Alpha iron, beta iron and gamma iron
Alpha iron and beta iron
Body centred cubic iron and face centred cubic iron
Alpha iron, gamma from and delta iron
Following elements have face-centred cubic structure
Gamma iron (910° to 1400°C), Cu, Ag, Au, Al, Ni, Pb, Pt
Mg, Zn, Ti, Zr, Br, Cd
A iron (below 910°C and between 1400 to 1539°C), W
All of the above
Hardness of martensite is about
RC 65
RC 48
RC 57
RC 80
Shock resisting steels should have
Low wear resistance
Low hardness
Low tensile strength
Toughness
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
German silver is an alloy of
Silver and some impurities
Refined silver
Nickel, Copper and zinc
Nickel and copper
The correct sequence for descending order of machinability is
Grey cast iron, low carbon steel, wrought iron
Low carbon steel, grey cast iron, wrought iron
Wrought iron, low carbon steel, grey cast iron
Wrought iron, grey cast iron, low carbon steel
The blade of a power saw is made of
Boron steel
High speed steel
Stainless steel
Malleable cast iron
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
When elements like nickel, chromium, copper and molybdenum are added to the molten cast iron, it produces
White cast iron
Nodular cast iron
Malleable cast iron
Alloy cast iron
Which of the following impurity in cast iron makes it hard and brittle?
Silicon
Sulphur
Manganese
Phosphorus
Delta-iron occurs between the temperature ranges of
400°C to 600°C
600°C to 900°C
900°C to 1400°C
1400°C to 1530°C
Which of the following is used for bearing liner?
Gun metal
Bronze
Bell metal
Babbitt metal
Closed packed hexagonal 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