## GATE ME Questions on Welding process (Production Engineering)

Question #1

In an arc welding process, welding speed is doubled. Assuming all other process parameters to be constant, the cross-section area of the weld beam will

(A)Increase by 25%

(B)Increase by 50%

(C)Decrease by 25%

(D)Decrease by 50%

[GATE 2017 Set 1, 1 mark]

Question #2

Under optimal conditions of the process, the temperatures experienced by a copper workpiece in fusion welding, brazing and soldering are such that

(A) Twelding > Tsoldering> Tbrazing

(B) Tsoldering > Twelding > Tbrazing

(C) Tbrazing >Twelding > Tsoldering

(D) Twelding > Tbrazing > Tsoldering

[GATE 2016 Set 1, 1 mark]

Question #3

The voltage-length characteristic of a direct current arc in an arc welding process is 𝑉 = 100 + 40𝑙, where 𝑙 is the length of the arc in mm and V is arc voltage in volts. During a welding operation, the arc length varies between 1 and 2 mm and the welding current is in the range 200-250 A. Assuming a linear power source, the short circuit current is_________ A.

[GATE 2016 Set 2, 2 marks]

Question #4

Spot welding of two steel sheets each 2 mm thick is carried out successfully by passing 4 kA of current for 0.2 seconds through the electrodes. The resulting weld nugget formed between the sheets is 5 mm in diameter. Assuming cylindrical shape for the nugget, the thickness of the nugget is________mm.

 Latent heat of fusion for steel 1400 kJ/kg Effective resistance of the weld joint 200 $\mu \Omega$ Density of steel 8000 kg/m3

[GATE 2016 Set 3, 2 marks]

Question #5

In a linear arc welding process, the heat input per unit length is inversely proportional to
(A) welding current
(B) welding voltage
(C) welding speed
(D) duty cycle of the power source

[GATE 2015 Set 1, 1 mark]

Question #6

A DC welding power source has a linear voltage-current (V-I) characteristic with open circuit voltage of 80 V and a short circuit current of 300 A. For maximum arc power, the current (in Amperes) should be set as_________

[GATE 2015 Set 1, 2 marks]

Question #7

During a TIG welding process, the arc current and arc voltage were 50 A and 60 V, respectively, when the welding speed was 150 mm/min. In another process, the TIG welding is carried out at a welding speed of 120 mm/min at the same arc voltage and heat input to the material so that weld quality remains the same. The welding current (in A) for this process is
(A) 40.00
(B) 44.72
(C) 55.90
(D) 62.25

[GATE 2015 Set 2, 2 marks]

Question #8

Which two of the following joining processes are autogeneous?
(i) Diffusion welding
(ii) Electroslag welding
(iii) Tungsten inert gas welding
(iv) Friction welding
(A) (i) and (iv)
(B) (ii) and (iii)
(C) (ii) and (iv)
(D) (i) and (iii)

[GATE 2015 Set 3, 1 mark]

Question #9

In solid-state welding, the contamination layers between the surfaces to be welded are removed by

(A) alcohol

(B) plastic deformation

(C) water jet

(D) sand blasting

[GATE 2014 Set 1, 1 mark]

Question #10

The major difficulty during welding of aluminium is due to its

(A) high tendency of oxidation

(B) high thermal conductivity

(C) low melting point

(D) low density

[GATE 2014 Set 1, 1 mark]

Question #11

Within the Heat Affected Zone (HAZ) in a fusion welding process, the work material undergoes
(A) microstructural changes but does not melt
(B) neither melting nor microstructural changes
(C) both melting and microstructural changes after solidification
(D) melting and retains the original microstructure after solidification

[GATE 2014 Set 4, 1 mark]

Question #12

For spot welding of two steel sheets (base metal) each of 3 mm thickness, welding current of 10000 A is applied for 0.2 s. The heat dissipated to the base metal is 1000 J. Assuming that the heat required for melting 1 mm3 volume of steel is 20 J and interfacial contact resistance between sheets is 0.0002 Ω, the volume (in mm3) of weld nugget is _______

[GATE 2014 Set 4, 2 marks]

Question #13

In a DC arc welding operation, the voltage-arc length characteristic was obtained as $V_{arc}=20+5l$ where the arc length l was varied between 5 mm and 7 mm. Here $V_{arc}$ denotes the arc voltage in Volts. The arc current was varied from 400 A to 500 A. Assuming linear power source characteristic, the open circuit voltage and the short circuit current for the welding operation are

(A) 45 V, 450 A

(B) 75 V, 750 A

(C) 95 V, 950 A

(D) 150 V, 1500 A

[GATE 2012, 2 marks]

practice other topics from Production Engineering:

Theory of Metal cutting

Machining

Casting