Secondary hardening in steels arises out of the
Precipitation of fine alloy carbides at high temperatures
Refinement of ferrite grain size by working
Decomposition of retained austenite upon heat treatment
Precipitation of complex inter-metallic upon heat treatment
Correct Answer :
C. Decomposition of retained austenite upon heat treatment
Related Questions
Specific gravity of a metal, which weighs 5 kg in air and 4 kg when submerged in water, will be
5
1.25
2.5
3.75
Identify the false statement
Martensitic steels are less susceptible to pitting corrosion than austenitic steels
Pitting corrosion is usually very localised
Hydrogen embrittlement is facilitated by tensile stress
Stress corrosion cracking is facilitated by tensile stress
In multipass welds, shot peening is done after each pass to
Close the surface porosity
Break the continuity of columnar grains
Flatten the weldment
Introduce texture in the weld
According to thermodynamic Fahrenheit scale, the fundamental interval between ice point to steam point is
180°
212°
32°
273°
Steels with high carbon equivalent have poor Weldability, because in these steels during welding
Carbon and other alloying elements get oxidised from the weld pool
Excessive ferrite forms in the heat affected zone leading to poor toughness of the weld
Martensite forms in the heat affected zone leading to poor toughness/ductility of the weld
Segregation of carbon and other element occurs in the weld pool leading to poor properties of the weld
Fine grained steels have
High brittleness
Higher tendency to distort
High ductility
None of these
Metallic surveying tapes are made of __________ which has a low co-efficient of expansion & enough strength.
Invar
Hastelloy
Duralumin
Monel metal
If a nuclear reactor produces more fissile nuclear fuel than it consumes, then it is called a __________ reactor.
Critical
Breeder
Fertile
Heterogeneous
Minimum thermal efficiency of a steam boiler may be around __________ percent
25
45
65
20
Which of the following represents the correct time-temperature curve when a block of metal is heated above room temperature & then left to cool in the room following Newton's law of cooling in which the rate of temperature drop will go on decreasing with the passage of time.
Which of the following is not an ore of copper?
Cryolite
Azurite
Chalcopyrite
Malachite
Oxygen cylinders used for autogenous (cutting/welding) purposes are
Seamless & made of steel
Heat treated before use
Made by sand casting
Welded steel cylinders
Production of one ton of paper in Indian paper industry consumes about __________ kWh of electricity.
300
800
1400
2000
Thermodynamic cycle involved in the working of a thermal power plant is the __________ cycle.
Joule
Carnot
Rankine
Brayton
For efficient performance of a blast furnace, the extent of reduction of Wustite (FeO) should be
100% indirect reduction
100% direct reduction
50-60% indirect reduction
30-40% indirect reduction
Which of the following properties of a solid is not dependent on crystal imperfection?
Ductility
Semi-conductivity
Melting point
Yield stress
In a boundary layer developed along the flow, the pressure decreases in the downstream direction. The boundary layer thickness in this case will
Decrease gradually
Increase gradually
Increase rapidly
Remain constant
Liquor poisoning generally occurs due to the presence of __________ in it.
Ethyl alcohol
Impurities
Methyl alcohol
Carbonic acid
Alloys having more than 80% copper are generally more
Abrasion resistant
Corrosion resistant
Prone to season cracking
Machinable
A jig is used while __________ a hole.
Boring
Counter boring
Drilling
Enlarging
A thin, flat & square plate measuring 2 m × 2 m is freely hanging in ambient air at 25°C. It is exposed to the solar radiation falling on one side of the plate at the rate of 500 W/m2. The plate temperature will remain constant at 30°C, if the convective heat transfer co-efficient is __________ W/m2 °C.
50
100
150
200
The yield point phenomenon observed in annealed low carbon steel is due to the presence of the following element.
Silicon
Carbon
Phosphorous
Chromium
Stellite is a __________ material.
Ferrous
Ceramic
Cemented carbide
Non-ferrous cast alloy cutting tool
Cementite is in the lamellar form in the __________ phase of steel.
Martenistic
Bainitic
Pearlitic
Ferritic
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
Nickel is a __________ material.
Ferromagnetic
Semi-conductor
Paramagnetic
Ferroelectric
Auto collimator is used to check
Flatness
Angle
Rotor balancing
Roughness
Often earing defects are found during deep drawing operation, because the
Surface finish of the sheet is poor
Sheet material has been given substantial spring back
Starting sheet has planer anisotropy due to its texture
Starting sheet has normal anisotropy due to its texture
Water hammer is caused in steam carrying pipelines, because of
Partial condensation of steam
Vibration of the pipeline
High degree of superheat of steam
Its exposure to torrential rain
Pick out the correct statement
Jet engine can work, where there is no atmosphere
Rocket engines cannot work, where there is no atmosphere
Rocket engines carry oxygen required for the combustion in the form of oxidiser
Jet engines also carry oxidiser