Sub zero treatment of steel is done to
Suppress martensite transformation
Enhance its working performance in sub zero atmosphere
Reduce the retained austenite in hardened steel
Induce temper brittleness after its hardening
Correct Answer :
C. Reduce the retained austenite in hardened steel
Related Questions
Gas turbine normally employs a constant __________ cycle.
Pressure
Temperature
Volume
None of these
Starting friction is low in case of the __________ lubrication.
Boundary
Hydrodynamic
Hydrostatic
Mixed/semi-fluid
A cylindrical rod subjected to a tensile strain within the elastic limit undergoes a volume change. If the volume strain is equal to half the tensile strain, then the Poisson's ratio of the rod is
0
0.33
0.44
0.25
LVDT used for displacement measurement is a/an __________ transducer.
Passive
Active
Capacitive
None of these
Lap joints are preferred over butt joints in soldering/brazing, because these joints are
Weaker in tension but stronger in shear
Weaker in shear but stronger in tension
Stronger in both shear and tension
The lap joints are easily made
In Imperial Smelting Process for extraction of zinc, zinc vapour thus produced is quenched in the external condenser by the use of the following:
Jet of water at high pressure
Blast of air
Mixture of water and air
Rain of molten lead
High relative humidity decreases the evaporative process and as the temperature is increased, the relative humidity decreases. The comfort range for human body is the ambient temperature of 22 to 27°C with relative humidity ranging from __________ percent.
5 to 10
15 to 25
45 to 50
75 to 80
An example of unsteady non uniform flow is the flow of liquid under pressure through a
Tapering pipe at constant flow rate
Tapering pipe at either decreasing or increasing flow rate
Long pipeline of constant diameter
None of these
Insulation of liquid surface can be achieved by __________ on top of its surface.
Floating hollow polypropylene spheres
Spraying alumina powder
Putting cement
None of these
Fatigue limit improvement by over stressing the metal by successively increasing the load is called coaxing. In fatigue failure, the material fails
Below the yield point
Above the yield point
Below the elastic limit
At the elastic limit
Which of the following are made out of the carbon steel having carbon content of 0.9 to 1%?
Small punches, broaches reamers and springs
Cutlery, screws, rivets and files
Mandrels, twist drills, small lathe tools and razors
Forgings like can shaft, structural steel plate, threading dies and drawing dies
Steel balls are manufactured by
Sintering
Casting
Cold heading
Spinning
Pick out the correct statement.
Hot worked materials are subjected to annealing to remove internal stresses
Annealing of steel hardens it slightly
Normalising of a material induces stresses
Tempering of a material improves ductility & toughness but reduces hardness & brittleness
Pick out the wrong statement.
Copper is the metal having the highest electronic conductivity
Hardenability & Weldability of metals are inversely related
Covalent bonding formed by sharing of electrons is present in all semi-conductor materials
Glass transition temperature applies to 'polymers' but not to 'glasses'
Tin based white metals are used, where bearings are subjected to
High pressure & load
Low pressure & load
High temperature
Large surface wear
__________ is the process of coating the surface of steel with aluminium oxide, thereby imparting it increased resistance to corrosion & oxidation upto a temperature of 700°C.
Veneering
Galvanising
Electroplating
Calorising
Fog is an example of colloidal system of
Solid dispersed in gas
Solid dispersed in liquid
Liquid dispersed in gas
Gas dispersed in liquid
In a totally irreversible isothermal expansion process for an ideal gas, ΔE = 0, ΔH = 0. Then ΔQ and ΔS will be
ΔQ = 0, ΔS=0
ΔQ = 0, ΔS = +ve
ΔQ = 0, ΔS = -ve
ΔQ = +ve, ΔS= +ve
At the point of boundary layer separation in fluid flow, the
Shear stress is maximum
Velocity gradient is flat
Density variation is maximum
Shear stress is zero
Atomic __________ is a whole number for an element.
Number
Weight
Radius
None of these
The co-ordination number in simple cubic structure is
4
6
8
12
Referring to the periodic table of elements, it is found that with increasing atomic number. The atomic size in the same
Period increases
Period decreases
Group increases
Both 'b' & 'c'
Hollow shafts can be made as strong as solid shafts by making the twisting moments of both the shafts same. Shafts made by __________ have residual stresses.
Forging
Cold rolling
Hot rolling
Casting
__________ wire is never used for making the heating element.
Nichrome
Kanthal
Invar
None of these
Eutectoid composition of carbon steel at room temperature is
Cementite
Pearlite
Martensite
Ferrite
Consider the equilibrium A(g) + B(g) = AB(g). When the partial pressure of A is 10-2 atm, the partial pressure of B is 10-3 atm and the partial pressure of AB is 1 atm, the equilibrium constant 'K' is
10 atm-1
105 atm-1
10 (dimensionless)
105 (dimensionless)
Case hardening is not done by
Nitriding
Hot dipping
Electroplating
Both b & c
Which of the following performance characteristics of a S.I engine is not affected by the front end volatility of the petrol used?
Vapour locking
Hot starting
Spark plug fouling
All 'a', 'b' & 'c'
Which of the following alloying elements is present in maximum percentage in high speed steel?
Molybdenum
Chromium
Tungsten
Vanadium
Dry saturated steam can be converted into superheated steam by
Increasing its cross-sectional area of flow
Passing it through a pressure reducing valve
Forcing it downwards through a vertical tube
None of these