59740514 1 2 Resistance and Special Welding Q a for Students

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Resistance WeldingWelding

By S K MondalCompiled by: S K Mondal Made Easy

IES‐2003In resistance welding, heat is generated due to the resistance between(a) Electrode and workpiece(b) Asperities between touching plates(b) Asperities between touching plates(c) Two dissimilar metals being in contact(d) Inter atomic forces

Ans. (b)

Compiled by: S K Mondal Made Easy

IES‐2001The maximum heat in resistance welding is at the(a) Tip of the positive electrode(b) Tip of the negative electrode(c) Top surface of the plate at the time of electric (c) Top surface of the plate at the time of electric

contact with the electrode(d) Interface between the two plates being Joined

Ans. (d)


GATE‐2008In arc welding of a butt joint, the welding speed isto be selected such that highest cooling rate isachieved. Melting efficiency and heat transferefficiency are 0.5 and 0.7, respectively. The area ofh ld d hthe weld cross section is 5 mm2 and the unitenergy required to melt the metal is 10 J/mm3. Ifthe welding power is 2 kW, the welding speed inmm/s is closest to(a) 4 (b) 14 (c) 24 (d) 34

Ans. (b)


GATE‐2006In an arc welding process, the voltage and currentare 25 V and 300 A respectively. The arc heattransfer efficiency is 0.85 and welding speed is 8mm/see. The net heat input (in J/mm) is(a) 64(b) 797(c) 1103(d) 79700

Ans. (b)


GATE‐2007Two metallic sheets, each of 2.0 mm thickness, are welded in a lap jointconfiguration by resistance spot welding at a welding current of 10 kA andwelding time of 10 millisecond. A spherical fusion zone extending up to the fullthickness of each sheet is formed. The properties of the metallic sheets aregiven as:ambient temperature = 293 Kmelting temperature = 1793 Klatent heat of fusion = 300 kJ/kgdensity = 7000 kg/m3

specific heat = 800 J/kg KAssume:(i) Contact resistance along sheet‐sheet interface is 500 micro‐ohm and alongelectrode‐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.The melting efficiency (in %) of the process is(a) 50.37 (b) 60.37 (c) 70.37 (d) 80.37

Ans. (c)


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GATE‐2005Spot welding of two 1 mm thick sheets of steel(density = 8000 kg/m3) is carried out successfullyby passing a certain amount of current for 0.1second through the electrodes. The resultant weld

f d d dnugget formed is 5 mm in diameter and 1.5 mmthick. If the latent heat of fusion of steel is 1400kJ/kg and the effective resistance in the weldingoperation in 200 , the current passing through theelectrodes is approximately(a) 1480A (b) 3300 A(c) 4060 A (d) 9400 A Ans. (c)


GATE‐2001Resistance spot welding is performed on twoplates of 1.5 mm thickness with 6 mm diameterelectrode, using 15000 A current for a timeduration of 0.25 seconds. Assuming the interface

b h h dresistance to be 0.0001 , the heat generated toform theweld is(a) 5625 W‐sec (b) 8437W‐sec(c) 22500 W‐sec (d) 33750W‐sec

Ans. (a)


GATE‐2004Two 1 mm thick steel sheets are to be spot weldedat a current of 5000 A. Assuming effectiveresistance to be 200 micro‐ohms and current flowtime of 0.2 second, heat generated during the

ll bprocesswill be(a) 0.2 Joule (b) 1 Joule(c) 5 Joule (d) 1000 Joules

Ans. (d)


GATE‐1992For resistance spot welding of 1.5 mm thick steelsheets, the current required is of the order of(a) 10 A(b) 100 A(b) 100 A(c) 1000 A(d) 10,000 A

Ans. (d)


GATE‐2010Two pipes of inner diameter 100 mm and outerdiameter 110 mm each joined by flash buttwelding using 30 V power supply. At the interface,1 mm of material melts from each pipe which hasa resistance of 42.4 Ω. If the unit melt energy isa resistance of 42.4 Ω. If the unit melt energy is64.4 MJm‐3, then time required for welding inseconds is(a) 1 (b) 5 (c) 10 (d) 20

Ans. (c)


IAS‐2003Assertion (A): Spot welding is adopted to weld twooverlapped metal pieces between two electrode points.Reason (R): In this process when current is switched on,the lapped pieces of metal are heated in a restricted area.(a) Both A and R are individually true and R is the correct(a) Both A and R are individually true and R is the correct

explanation of A(b) Both A and R are individually true but R is not the

correct explanation of A(c) A is true but R is false(d) A is false but R is true

Ans. (a)


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Calculate the melting efficiency in the case of arcwelding of steel with a potential of 20 V and current of200 A. The travel speed is 5 mm/s and the cross‐sectional area of the joint is 20 mm2. Heat required to

Example‐1

melt steel may be taken as 10 J/ and the heat transferefficiency as 0.85.

[PTU ‐2004]


Example‐2Calculate the melting efficiency in the case ofarc‐welding of steel with a potential of 20 V anda current of 200 A. The travel speed is 5 mm/sand the cross‐sectional area of the joint is 20and .the cross sectional area of the joint is 20mm2. Heat required to melt steel may be takenas 10 J/mm3 and the heat transfer efficiency as0.85.


Example‐3Two steel plates each 1 mm thick are spotwelded at a current of 5000 A. The current flowtime is 0.1 s. The electrodes used are 5 mm indiameter Determine the heat generated anddiameter. Determine the heat generated andits distribution in the weld zone. The effectiveresistance in the operation is 200 μΩ.


Example‐4Two steel sheets of 1.0mm thickness areresistance welded in a lap joint with a current of10 000 A for 0.1 second. The effective resistanceof the joint can be taken as 100 micro ohms Theof the joint can be taken as 100 micro ohms. Thejoint can be considered as a cylinder of 5 mmdiameter and 1.5mm height. The density of steelis 0.00786 g/mm3 and heat required for meltingsteel is 10 J/mm3.


How much heat would be generated in the spotwelding of two sheets of 1 mm thick steel thatrequired a current of 10000 A for 0.1 seconds?

Example‐5

qAn effective resistance of 100 μΩ. is assumed.


Example‐6Two 1.2 mm thick, flat copper sheets are being spotwelded using a current of 6000 A and a current flowtime of t = 0.18 s. The electrodes are 5 mm in diameter.Estimate the heat generated in the weld zone. Takeeffective resistance as 150 μΩ.


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Example‐7Two steel sheets of 1.0‐mm thickness are resistancewelded in a projection welding with a current of 30000 A for 0.005 second. The effective resistance of thejoint can be taken as 100 micro ohms. The joint can be

d d l d f d dconsidered as a cylinder of 5 mm diameter and 1.5 mmheight. The density of steel is 0.00786 g/mm3 and heatrequired for melting steel is 10 J/mm3.


Other Welding h iTechnique


IES‐2000Consider the following processes:1. Gas welding 2. Thermit welding3. Arc welding3 g4. Resistance weldingThe correct sequence of these processes in increasing order of their welding temperatures is(a) 1, 3, 4, 2 (b) 1, 2, 3, 4(c) 4, 3, 1, 2 (d) 4, 1, 3, 2

Ans. (d)Compiled by: S K Mondal Made Easy

IAS‐2003Which one of the following is not an electric resistance method of welding?(a) Electro slag welding(b) Percussion welding(b) Percussion welding(c) Seam welding(d) Flash welding

Ans. (a)


IAS‐2000Consider the following welding processes:1. TIG welding 2. Submerged arc welding3. Electro‐slag welding 4. Thermit weldingWhi h f th ldi d f ldi Which of these welding processes are used for welding thick pieces of metals?(a) 1, 2 and 3 (b) 1, 2 and 4(c) 1,3 and 4 (d) 2, 3 and 4

Ans. (d)


IES‐2004Assertion (A): In electron beam welding process,vacuum is an essential process parameterReason (R): Vacuum provides a highly efficientshield onweld zone(a) Both A and R are individually true and R is the

correct explanation of A(b) Both A and R are individually true but R is not the



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IES‐2002In which one of the following welding techniques is vacuum environment required?(a) Ultrasonic welding(b) Laser beam welding(b) Laser beam welding(c) Plasma arc welding(d) Electron beam welding

Ans. (d)


IES‐1993Electron beam welding can be carried out in(a) Open air(b) A shielding gas environment ( ) A i d i t h b(c) A pressurized inert gas chamber(d) Vacuum

Ans. (d)


IAS‐2004Which one of the following welding processes consists of smaller Heat Affected Zone (HAZ)?(a) Arc welding (b) Electron beam welding(c) MIG welding (d) Thermit welding(c) MIG welding (d) Thermit welding

Ans. (b)


IES 2007Consider the following statements in respect of the laser beam welding:1. It can be used for welding any metal or their

combinations because of very high temperature of the focal pointsfocal points.

2. Heat affected zone is very large because of quick heating.

3. High vacuum is required to carry the process.Which of the statements given above is/are correct?(a) 1 and 2 only (b) 2 and 3 only(c) 1 only (d) 1, 2 and 3

Ans. (c)Compiled by: S K Mondal Made Easy

IES‐2006Which one of the following welding processes consists of minimum heat affected zone (HAZ)?(a) Shielded Metal Arc Welding (SMA W)(b) Laser Beam Welding (LBW)(b) Laser Beam Welding (LBW)(c) Ultrasonic Welding (USW)(d) Metal Inert Gas Welding (MIG)

Ans. (b)


IAS‐2007Consider the following welding processes:1. Arc welding 2. MIG welding3. Laser beam welding 4. Submerged arc

weldingweldingSelect the correct sequence in increasing order of Heataffected zone (HAZ) using the codegiven below:(a) 1 ‐ 2 ‐ 3 – 4 (b) 1 ‐ 4 ‐ 2 – 3(c) 3 ‐ 2 ‐ 4 – 1 (d) 4 ‐ 3 ‐ 2 – 1


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IAS‐1999Match List I (Shielding method) with List II (Weldingprocess) and select the correct answer using the codesgiven below the lists:List I List IIA. Flux coating 1. Gas metal arc weldingB Fl l S b d ldiB. Flux granules 2. Submerged arc weldingC. CO2 3. Shielded metal arc weldingD. Vacuum 4. Laser beamwelding

5. Electron beam weldingCodes:A B C D A B C D(a) 1 2 5 3 (b) 1 4 2 5(c) 3 5 1 4 (d) 3 2 1 5

Ans. (d)


GATE‐2007Which one of the following is a solid state joining process?(a) Gas tungsten arc welding(b) Resistance spot welding(b) Resistance spot welding(c) Friction welding(d) submerged arc welding

Ans. (c)


GATE‐1992In an explosive welding process, the……….. (maximum/minimum) velocity of impact is fixed by the velocity of sound in the……………… (flyer/target) plate material(a) Maximum; target(b) Minimum; target(c) Maximum; flyer(d) Minimum; flyer


IES 2011 S‐1 Contd…Match List –I with List –II and select the correct answer using the code given below the lists:List‐I List –II

A. Laser beam welding

1. Can be applied for welding or refractory metals like niobium, tantalum, molybdenum and tungsten.

B. Electron 2. A sound and clean welded joint is created due to beam welding rubbing of two parts against each other with

adequate speed and pressure producing intense heat raising temperature above melting point.

C. Ultrasonic welding

3. Clean heat source created much away from job, a narrow spot is heated, work chamber operates in a high vacuum.

D. Friction welding

4. Clean heat source very quick heating, very small focal spot, no vacuum chamber is required.


IES 2011 From S‐1Codes :

A B C D A B C D(a) 4 3 1 2 (b) 2 3 1 4(c) 4 1 3 4 (d) 2 1 3 4( ) 4 3 4 ( ) 3 4

Ans. (a)


IES‐2009Match List‐I with List‐II and select the correct answer using the code given below the Lists:List‐I List‐II(Welding Process) (Application)

A. Laser welding 1. Uniting large‐area sheetsB. Friction welding 2. Repairing large partsC Ultrasonic welding 3 Welding a rod to a flat surfaceC. Ultrasonic welding 3. Welding a rod to a flat surfaceD. Explosive welding 4. Fabrication of nuclear reactor

components 5. Welding very thin materials

Code:(a) A B C D (b) A B C D

5 4 3 2 1 4 2 5

(c) A B C D (d) A B C D1 3 4 2 5 3 4 1

Ans. (d)


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IAS‐2002Match List I, (Welding) with List II (Application) and select the correct answer using the codes given below the Lists:List I List II(Welding) (Application)A. Explosive 1. Joining thick sheetsB. Ultrasonic 2. Manufacture of heat exchangesgC. Thermit 3. Joining thin sheets or wires of

similar/dissimilar metalsD. Projection 4. Joining hydraulic piston rods for

agricultural machinery5. Joining rails, pipes and thick steel

sectionsCodes:A B C D A B C D(a) 2 5 1 3 (b) 4 5 1 3(c) 2 3 5 1 (d) 4 3 5 1

Ans. (c)


IAS‐2001Match List I (Welding processes) with List II (Features) and select the correct answer using the codes given below the Lists:

List I List IIA. Ultrasonic welding 1. Gas heated to ionized condition

for conduction of electric currentB. Electron beam welding 2. High frequency and high

intensity vibrationsC. Plasma arc welding 3. Concentrated stream of high‐

energy electrons4. Exothermal chemical reaction

Codes: A B C A B C(a) 1 2 4 (b) 4 3 1(c) 2 1 4 (d) 2 3 1


JWM 2010Match List‐I with List‐II and select the correct answer using the code given below the lists :

List I List IIA. Atomic hydrogen welding

1. Two pieces are brought together and power supply is switched on

B Plasma arc 2 Nugget is formed at the interface of

Code:A B C D A B C D(a) 4 3 2 1 (b) 1 3 2 4(c) 4 2 3 1 (d) 1 2 3 4

B. Plasma‐arc welding

2. Nugget is formed at the interface of two plates

C. Spot welding 3. Gas is ionizedD. Flash welding 4. Inert gas shielded arc welding


Brazing and Solderingg g


GATE‐2005The strength of a brazed joint(a) Decreases with increase in gap between the two joining surfaces(b) Increases with increase in gap between the two j i i fjoining surfaces(c) Decreases 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

Ans. (d)


IES‐2006Which one of the following is not a fusion welding process?(a) Gas welding(b) Arc welding(b) Arc welding(c) Brazing(d) Resistance welding

Ans. (c)


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IES‐1994Match List ‐ I with List ‐ II and select the correct answer using the codes given below the Lists:List ‐ I (Filler) List ‐ II (Joining process)A. Cu, Zn, Ag alloy 1. Braze welding.B. Cu, Sn, alloy 2. BrazingC. Pb, Sb, alloy 3. SolderingD.Iron oxide and aluminium powder 4. TIG welding of

aluminiumCodes:A B C D A B C D(a) 2 1 3 ‐ (b) 1 2 4 ‐(c) 2 1 3 4 (d) 2 ‐ 3 4

Ans. (a)


IAS‐1996Match List I with List II and select the correct answer using the codes given below the listsList –I List‐II(Filler rod material) (Joining process)A. Mild steel 1. MIG weldingB. Bronze 2. SolderingC. Brass 3. BrazingD. Lead and tin alloy 4. Thermit welding

5. Braze weldingCodes:A B C D A B C D(a) 1 5 3 2 (b) 4 3 2 5(c) 4 3 5 2 (d) 1 3 5 4

Ans. (a)


IES‐2004Match List I (Welding problems) with List II (Causes) and select the correct answer using the codes given below the Lists:List I List IIA. Cracking of weld metal 1. Excessive stressesB. Cracking of base metal 2. High joint rigidityC Porosity 3 Failure to remove slag C. Porosity 3. Failure to remove slag

from previous depositD. Inclusions 4. Oxidation

5. Excessive H2, O2, N2, in the welding atmosphere

Codes:A B C D A B C D(a) 2 1 5 3 (b) 3 4 2 1(c) 2 4 5 3 (d) 3 1 4 2

Ans. (a)


IES‐2003Match List I(Welding Defects) with List II (Causes) and select the correct answer using the codes given below the Lists:List‐I List II(Welding Defects) (Causes)A S D l dA. Spatter 1. Damp electrodesB. Distortion 2. Arc blowC. Slag inclusion 3. Improper cleaning in

multi‐pass weldingD. Porosity 4. Poor joint selectionCodes:A B C D A B C D(a) 4 2 3 1 (b) 4 2 1 3(c) 2 4 1 3 (d) 2 4 3 1


IES‐2004Consider the following statements:The magnitude of residual stresses in weldingdepends upon1. Design of weldment

S d l f2. Support and clamping of components3. welding process used4. Amount of metal melted / depositedWhich of the statements given above are correct?(a) 1, 2 and 4 (b) 1, 2 and 3(c) 1 and 3 (d) 2 and 3

Ans. (b)Compiled by: S K Mondal Made Easy

GATE‐2003Match the followingWork material Type of joiningP. Aluminium 1. Submerged Arc WeldingQ. Die Steel 2. SolderingR. Copper Wire 3. ThermitWeldingS. Titanium sheet 4. Atomic Hydrogen Welding

5. Gas Tungsten Arc Welding6. Laser Beam Welding7. Brazing

(a) P ‐ 2 Q ‐ 5 R ‐ 1 S ‐ 3(b) P ‐ 6 Q ‐ 3 R ‐ 4 S ‐ 4(c) P ‐ 4 Q‐ 1 R ‐ 6 S ‐ 2(d) P ‐ 5 Q ‐ 4 R ‐ 2 S – 6

Ans. (d) Compiled by: S K Mondal Made Easy

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IES‐2004Consider the following statements:The size of the heat affected zone (HAZ) will increase with1. Increased starting temperature2. Increased welding speed2. Increased welding speed3. Increased thermal conductivity of the base metal4. Increase in base metal thicknessWhich of the statements given above are correct?(a) 1, 2 and 3 (b) 1 and 3(c) 1 and 4 (d) 2 and 3

Ans. (b)Compiled by: S K Mondal Made Easy

IES‐1992Weld spatter occurs due to any of the following except(a) High welding current(b) Too small an electrode(b) Too small an electrode(c) Arc(d) Wrong polarity

Ans. (d)


JWM 2010Assertion (A) : Spatter is one of thewelding defects.Reason (R) : In submerged arc welding process,there is no spatter of molten metal.(a) Both A and R are individually true and R is thecorrect explanation of Acorrect explanation of A(b) Both A and R are individually true but R is not the


Ans. (b)


IES‐1998An arc welded joint is shown in the above figure. The part labelled 'B' in the figure is known as(a) Weld preparation (b) Penetration (c) Reinforcement (d) Slag

Ans. (c)


IES‐2004Assertion (A): A sound welded joint should not onlybe strong enough but should also exhibits a goodamount of ductilityReason (R): Welding process is used for fabricatingmild steel components onlymild steel components only(a) Both A and R are individually true and R is the correct

explanation of A(b) Both A and R are individually true but R is not the



IAS‐2003Tool material not suited to resistance welding is(a) Aluminium oxide (b) Stellite(c) High speed steel (d) Masonite

Ans. (a)


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GATE‐1996Preheating before welding is done to(a) Make the steel softer(b) Bum away oil, grease, etc, from the plate surface(c) Prevent cold cracks(c) Prevent cold cracks(d) Prevent plate distortion

Ans. (c)


IES 2011Cold‐cracking in steel weldments depends on

1. Carbon equivalent2. Heat input3. Effective thickness H d i ld l3. Hydrogen content in weld pool

(a) 1, 2 and 3 only(b) 1, 2 and 4 only(c) 2, 3 and 4 only(d) 1, 2, 3 and 4

Ans. (d)


GATE‐2001Two plates of the same metal having equalthickness are to be butt welded with electric arc.When the plate thickness changes, welding isachieved by(a) Adjusting the current(b) Adjusting the duration of current(c) Changing the electrode size(d) Changing the electrode coating

Ans. (a)

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59740514 1 2 Resistance and Special Welding Q a for Students