GATE QUESTIONS ON WELDING
Previous Years GATE Questions on Joining Process 2005-2011
Solved GATE Questions on Joining Process
Question 1. Spot welding of two 1 mm thick sheets of steel (density=8000 kg/ ) is
carried out successfully by passing a certain amount of current for 0.1 second through the
electrodes. The resultant weld nugget formed is 5 mm in diameter and 1.5 mm thick. If the
latent heat of fusion of steel is 1400 kJ/kg and the effective resistance in the welding
operation in 200Ω, the current passing through the electrodes is approximately
(A) 1480 A
(B) 3300 A
(C) 4060 A (CORRECT)
(D) 9400 A
GATE-ME-2005
Question 2. The strength of a brazed joint
(A) Decrease with increase in gap between the two joining surfaces
(B) Increase with increase in gap between the two joining surfaces
(C) Decrease up to certain gap between the two joining surfaces beyond which it increases
(D) Increases up to certain gap between the two joining surfaces beyond which it
decreases
(CORRECT)
GATE-ME-2005
Question 3. In an arc welding process, the voltage and current are 25 V and 300 A
respectively. The arc heat transfer efficiency is 0.85 and welding speed is 8 mm/sec. The
net heat input (in J/mm) is :
(A) 64
(B) 797
(C) 1103
(D) 79700
Hint 3. (Ans B)
Power generated=VI
Heat input
GATE-ME-2006
Question 4. Two metallic sheets, each of 2.0 mm thickness, are welded in a lap joint
configuration by resistance spot welding at a welding current of 10 kA and welding time of
10 milli second. A spherical fusion zone extending up to the full thickness of each sheet is
formed. The properties of the metallic sheets are given as:
Ambient temperature = 293 K
Melting temperature = 1793 K
Density =7000 kg/
Latent heat of fusion=300 kJ/kg
Specific heat =800 J/kg K
Assume : (i) contact resistance along sheet—sheet interface is 500 micro-ohm and
along electrode—sheet interface is zero; (ii) no conductive heat loss through the bulk
sheet materials; and (iii) the complete weld fusion zone is at the melting
temperature.
(A) 50.37
(B) 60.37
(C) 70.37
(D) 80.37
Hint 4. (Ans C)
Heat generated due to current,
Heat required for melting,
Since fusion zone is spherical in shape, therefore
Where r=t=thickness of sheet=2mm
Melting efficiency=70.35 %
GATE-ME-2007
Question 5. A direct current welding machine with a linear power source characteristic
provides open circuit voltage of 80 V and short circuit current of 800 A. During welding the
machine, the measured arc current is 500 A corresponding to an arc length of 5.0 mm and
the measured arc current is 460 A corresponding to an arc length of 7.0 mm. the linear
voltage (E)-arc length (L) characteristic of the welding arc can be given as (where E is in
volt and L is in mm)
(A) E=20+2L
(B) E=20+8L
(C) E=80+2L
(D) E=80+8L
Hint 5. (Ans A)
From power–source characteristics,
Arc voltage characteristics,
Equating (i) and (ii), we get
From equation (iii) and (iv), we get b=2 a=20
GATE-ME-2007
Question 6. Which one of the following is a solid state joining process?
(A) Gas tungsten arc welding
(B) Resistance spot welding
(C) Friction welding
(D) Submerged arc welding
GATE-ME-2007
Question 7. In arc welding of a butt joint, the welding speed is to be selected such that
highest cooling rate is achieved. Melting efficiency and heat transfer efficiency are 0.5 and
0.7 respectively.the artea of the weld cross-section is and the unit energy required
to melt the metal is . If the welding power is 2 kW, the welding speed in mm/s
is closest to
(A) 4
(B) 14
(C) 24
(D) 34
GATE-ME-2008
Hint 7. (Ans B)
Welding power applied=Heating power needed
Question 9. Which one of the following welding processes used non–consumable
electrode?
(A) Gas metal arc welding
(B) Submerged arc welding
(C) Gas tungsten arc welding
(D) Flux coated arc welding
GATE-ME-2011
RESISTANCE WELDING
The unit melting energy for a certain sheet metal to be spot welded is Um= 10.0 J/mm3. The
thickness of each the sheets to be welded= 3.0 mm. To achieve required strength, it is
desired to form a weld nugget that is 6.0 mm in diameter and 4.5 mm thick. The weld
duration is set at 0.2 sec. It is assumed that the total electrical resistance between the
surfaces = 125 micro-ohms and that only one-third of the electrical energy will be utilized to
form the nugget. Determine the minimum current level required for the operation
