Preheating before welding is done to
Make the plate softer
Burn oil & grease sticking to plate surfaces
Avoid plate distortion
Prevent cold cracks
Correct Answer :
D. Prevent cold cracks
Related Questions
Stainless steel is welded using
Oxy-acetylene flame
Oxy-hydrogen flame
Arc welding
Inert gas arc welding
Joining of thin foils is preferred to be done by
Gamma rays
X-rays
Microwaves
Gas welding
The refractory brick which has good thermal shock resistance at high temperature but cracks on cooling below 400°C is
Magnesite
Chrome
Silica
Fireclay
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
The kinematic viscosity (in stoke) and the absolute/dynamic viscosity (in poise) are the same for __________ at room temperature.
Air
Water
Mercury
Alcohol
Laser is a device to produce
Gamma rays
Microwaves
A beam of white light
A beam of coherent light
Faraday's law of electrolysis is related to the
Cation speed
Atomic number of the cation
Equivalent mass of the electrolyte
None of these
Metalloids
Are good conductor of heat & electricity
Act as electron donors with metals & as electron acceptor with non-metals
Are not necessarily solids at room temperature
Are compounds that exhibit both metallic & non-metallic properties to some extent and are exemplified by elements like germanium, silicon & boron
Wrought iron is never shaped by
Casting
Cold working
Forging
Welding
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'
Viscoelastic behaviour is observed in __________ materials.
Non-crystalline organic polymeric
Ceramic
All crystalline
All amorphous
__________ is a special constituent of chlorophyll without which photosynthesis is not possible.
Calcium
Nitrogen
Phosphorous
Hydrogen
To improve the machinability of steel, it is generally subjected to
Spheroidising
Tempering
Normalising
Annealing
Two solutions A1 & A2 have pH value of 2 & 6 respectively. It implies that the solution
A1 is more alkaline than solution A2
A1 is highly acidic
A2 is very slightly acidic
Both (B) & (C)
Pick out the wrong statement.
Cold cracking of a weld is due to the presence of hydrogen gas in the weld
True stress is given by, σ = σE (1 + εE), where σE and εE are engineering stress and engineering strain respectively
Phosphorous can be easily recovered in the iron blast furnace
High residual stress at the surface is beneficial for fatigue properties of a material
Wrought iron is not
Ductile & resistant to corrosion/rusting
Weldable easily
Having uniform strength in all directions
Having maximum tensile strength along the lines of slag distribution
Plastics as a material of construction suffer from the drawback of low
Machinability
Density
Strength
Plastic deformation
Limestone is added in the blast furnace (during pig iron manufacture) to
Form slag by combining with impurities
Supply heat by undergoing exothermic reaction with impurities
Reduce the coke consumption
Reduce slag viscosity
Which of the following is an undesirable property of slag produced during the Pyrometallurgical method of metal extraction from its ore?
High fusibility & fluidity
High thermal conductivity
Low density
High chemical activity
Material of construction of the electrode used in the electric resistance welding is
Stainless steel
Graphite
Copper
Steel
Enzymes belong to the category of
Proteins
Carbohydrates
Vitamins
Fats
Absolute zero, pressure will occur, when the molecular momentum of the system becomes zero. A liquid will cease to exist as liquid at
High vacuum
Zero pressure
0°K
Earth's centre
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
Nickel is a __________ material.
Ferromagnetic
Semi-conductor
Paramagnetic
Ferroelectric
__________ is the most suitable lubricant for drawing mild steel wires?
Kerosene
Water
Sodium stearate
Lime water
Atomic __________ is a whole number for an element.
Number
Weight
Radius
None of these
Work required for compression of a gas contained in a cylinder is 7000 kJ. During compression, heat interaction of 3000 kJ causes the surroundings to be heated. Internal energy change of the gas during the compression is __________ kJ.
+4000
-4000
10000
-10000
Aluminium is extracted from
Chalcocite
Bauxite
Galena
None of these
Hot extrusion of aluminium is done in the temperature range of __________ °C.
550-600
450-500
350-400
250-300
Mho's scale of hardness, which consists of 10 standard minerals is used for the measurement of __________ hardness.
Scratch
Indentation
Dynamic
Rebound