casting, welding, machine tools, material sc

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e a as ng

y on a

an cast ng

mould material.

other materials, such as clay and water, to improve

,packed around a pattern that has the shape of the.

The pattern must be removed before pouring, themo s usua y ma e n wo or more p eces.

An opening called asprue holeis cut from the top ofthe mold through the sand and connected to asystem of channels calledrunners. Contd.

The molten metal is poured into the sprue hole, flowsroug e runners, an en ers e mo cav y

through an opening called agate.

rav ty ow s t e most common means ointroducing the metal into the mold.

After solidification, the mold is broken and thefinished casting is removed.

The casting is then fettled by cutting off the ingateand the feeder head.

Because the mold is destroyed, a new mold must be.

Contd

Sequentialstepsinmakingasandcasting

andtop(cope)halvesofaflask,withthebottomsideup.

Sandisthenpackedintothedraghalfofthemold.

Abottomboardis ositionedonto ofthe ackedsand

andthemoldisturnedover,showingthetop(cope)halfof atternwiths rue andriser insin lace.

ecope a o t emo st enpac e w t san .

Contd

The mold is opened, the pattern board is drawn,

surface of the sand.

The mold is reassembled with the pattern boardremoved, and molten metal is poured through the

sprue.

The contents are shaken from the flask and the metalsegment is separated from the sand, ready for further

rocessin .

CastingTerms

Flask: A moulding flask is one which holds the sand

mou ntact. t s ma e up o woo or temporary

a lications or metal for lon term use.

Drag:Lower moulding flask.

Cope:Upper moulding flask.

Cheek: Intermediate moulding flask used in three

piece moulding.

ContdFor-2015 (IES, GATE & PSUs) Page 1 of 240 Rev.0


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Threeflaskmould

Pattern: Pattern is a replica of the final object to be

made with some modifications.

Parting line:This is the dividing line between the two

moulding f lasks that makes up the sand mould.

,

which is used at the start of the mould making.

Contd

Moulding sand: The freshly prepared refractory

material used for making the mould cavity. It is a

,

proportions.

Backing sand: This is made up of used and burnt

sand.

ore: se or ma ng o ow cav t es n cast ngs.

Pouring basin:A small funnelshaped cavity at the top

of the mould into which the molten metal is poured.

Sprue: The passage through which the molten metal

.

Runner:The passage ways in the parting plane through

which molten metal f low is regulated before they reach

the mould cavity.

metal enters the mould cavity in a controlled rate. Contd

mould cavity.

Chill: Chills are metallic objects, which are placed in

the mould to increase the cooling rate of castings.

casting so that hot metal can f low back into the mould

cavity when there is a reduction in volume of metal due

o so ca on

Contd

Padding aper ng o t nner sect on towar s t c er sect on

is known as 'padding'.

This will require extra material.

If padding is not provided, centre line shrinkage orporosity will result in the thinner section.

IES2001

The main purpose of chaplets is

(a) To ensure directional solidification

(b) To provide efficient venting

(c) For aligning the mold boxes

o support t e cores

IES1996

Which of the following methods are used for

o ta n ng rect ona so cat on orr ser es gn

1. Suitable lacement of chills

2. Suitable placement of chaplets

3. Employing padding

Select the correct answer.

a 1 an 2 1 an 3 c 2 an 3 1, 2 an 3

IES2007

Which one of the following is the corrects a emen

Gate is provided in moulds to

(a) Feed the casting at a constant rate

b Give assa e to ases

(c) Compensate for shrinkage

vo cav es

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CastingYield

Thecastingyieldistheproportionoftheactualcastin mass,w,tothemassofmetal ouredintothemould,W,expressedasapercentage.

= w

W

a ng ys em

Contd

top of the mould into which the molten metal isoured.

prue: e passage t roug w c t e mo ten meta ,

from the pouring basin, reaches the mould cavity. Inmany cases t contro s t e ow o meta nto t emould.

Contd

Runner: A runner is commonly a horizontal channel

which connects the sprue with gates, thus allowing the

.

are of larger crosssection and often streamlined to

slow down and smooth out the flow, and are designed

to provide approximately uniform f low rates to the

.

commonly made trapezoidal in crosssection.

Contd

Ingate:Achannelthroughwhichthemoltenmetalentersthemouldcavity.

Vent:Smallopeninginthemouldtofacilitateescapeofairandgases.

Typeso ateorIngate

Top gate: Causes tur u ence in t e mou cavity, it is prone

to form dross, favourable temperature gradient towards the

gate, only for ferrous alloys.

Bottom gate:No mould erosion, used for very deep moulds,

,

gradients.

Parting Gate: most widely used gate, easiest and mosteconomical in preparation.

Step Gate:Used for heavy and large castings, size of ingatesare normally increased from top to bottom.

IES2011,

that:

1. t avo s asp rat on

2. It avoids turbulence

3. The path of runner is reduced in area so thatunequal volume of f low through each gate

takes place

(c) 2 and 3 only (d) 1, 2 and 3

ATE 1 PI

ur ng t e ng process o a g ven san mou cav ty y

molten metal through a horizontal runner of circular cross

section the frictional head loss of the molten metal in the

runner w ncrease w e

(a) increase in runner diameter

(b) decrease in internal surface roughness of runner

(c) decrease in length of runner



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GATE2014(PI)

For a given volume of a riser, if the solidification

quadrupled, the surface area of the riser should be

made

(a) onefourth (b) half

(c) double (d) four t imes

A cylindrical riser of 6 cm diameter and 6 cm height has

to be designed for a sand casting mould for producing a

steel rectangular plate casting of 7 cm 10 cm 2 cm

.

minute. The total solidification time (in minute) of the

riser is ..

GATE2003

With a solidification factor of 0.97 x 106 s/m2, the

solidification time (in seconds) for a spherical

casting of 200 mm diameter is

a 539 107 c 4311 3233

IES2006

According to Chvorinov's equation, the

so cat on t me o a cast ng s proport ona to:

2

(b) v

(c) 1/v

(d) 1/v2

Where, v = volume of casting

GATE 2010(PI)o cat on t me o a meta c a oy cast ng s

(b) Directly proportional to the specific heat of the

cast material

(c) Directly proportional to the thermal diffusivity of

t e mo ten meta

temperature.

GATE2007

Volume of a cube of side 'l' and volume of a sphere of

radius r are equal. Both the cube and the sphere are solid

an o same mater a . ey are e ng cast. e rat o o t e

solidification time of the cube to the same of the sphere is:

( ) ( ) ( ) ( )3 6 2 2 3 2 4

4 r 4 r 4 r 4 ra b c d

,

equal volumes are separately cast from the same molten

metal under identical conditions. The height and

diameter of the cylinder are equal. The ratio of the

(a) 1.14 (b) 0.87

(c) 1.31 (d) 0.76

GATE2009(PI)A solid cylinder of diameter D and height equal to D, and a solid

cube of side L are being sand cast by using the same material.

Assuming there is no superheat in both the cases, the ratio of

solidification time of the cylinder to the solidification time of the

cube is

2

(b) (2L/D)2

(c) (2D/L)2

d D L 2



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era oo sur aceareao vo ume oraun vo umeo

riserisminimumincaseof

(a)Cylindricalriser

(b)Sphericalriser

(c)Hemisphericalriser

(d)Cuboidsriser

A round casting is 20 mm in diameter and 50 mm in

length. Another casting of the same metal is elliptical in

cross sect on, w t a ma or to m nor ax s rat o o 2, an

has the same len th and crosssectional area as the

round casting. Both pieces are cast under the same

conditions. What is the difference in the solidification

t mes o t e two cast ngs 10 ar sAreaof ellipse ab=

( )2 2

Circumference 3 3 3

2 / 2 (approx.)

a a a

a b

= + + +

= +

ConventionalQuestionESE2003

risers of the same volume with one has cylindrical shape

and other is parallopiped. [30 Marks]

GATE2014cy n r ca n r ser w t ameter an e g t , s

placed on the top of the mold cavity of a closed typesan mo as s own n e gure. e r ser s oconstant volume, then the rate of solidification in the

Sprue basin

r ser s t e east w en t e rat o : s

d

a 1 : 2 b 2 : 1Riser h(c) 1 : 4 (d) 4 : 1

Mold cavity

o u us e o

t as een emp r ca y esta s e t at t e mo u us

of the riser exceeds the modulus of the casting by a

factor of 1.2, the feeding during solidification would be

satisfactory.

R .

Modulus = volume/Surface area

In steel castings, it is generally preferable to choose a

riser with a heighttodiameter ratio of 1.Contd

22D D

+

Conventional uestionIES2008

Calculate the size of a cylindrical riser (height and diameter

equal) necessary to feed a steel slab casting of dimensions

,

into the mould.

[Use Modulus Method]

10 ar s

a ne s e o =

theriser. ( )Casting

AV

( )Riser

AV

=

er sers ou so y astsox>1

AccordingtoCaine X = c

Y b +

Y= anda,b,careconstant.risercasting

V



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Crucible Furnace or Pot Furnace Induction Furnace


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ec r c rc urnace

,

openhearth type of furnaces

with electric arc or oil fired

view of the large heat required

for melting.

suitable for ferrous materials and

are larger in capacity.

Crucible Furnace or Pot Furnace

Smaller foundries generally prefer the crucible furnace.

The crucible is enerall heated b electric resistanceor gas flame.

Induction Furnace

The induction furnaces are used for all types ofmaterials, the chief advantage being that the heatsource is isolated from the charge and the slag and fluxget the necessary heat directly from the charge insteadof the heat source.

Ladles

Twotypesofladlesusedinthepouringofcastings.

Castin Cleanin fettlinImpuritiesinthemoltenmetalarepreventedfromreaching

themouldcavitybyprovidinga

(i) Strainer

(iii)Skimbob

GATE1996

Light impurities in the molten metal are preventedrom reac ng e mou cav y y prov ng a

(a) Strainer

(b) Button well

c Skim bob(d) All of the above

Where A=AreaofmouldA.H

= e g o mou

Ag=AreaofGate

A

g mA 2gh=

Hm=Gateheight

Timetakentofillthemouldwithbottomgate

( )B m mt h h HA 2g

=

GATE2005

A mould has a downsprue whose length is 20 cman e cross sec ona area a e ase o edownsprue is 1cm2. The downsprue feeds a

or zon a runner ea ng n o e mou cav y ovolume 1000 cm3. The time required to fill themou cav y w e

(a)4.05 s (b)5.05 s (c)6.05 s (d)7.25 s

In a sand casting operation, the total liquid head ismaintained constant such that it is equal to the mouldheight. The time taken to fill the mould with a top gates tA. t e same mou s e w t a ottom gate,

then the time taken is tB. Ignore the time required tot e runner an r ct ona e ects. ssume

atmospheric pressure at the top molten metal surfaces.

e re at on etween tAan tB s(A) 2B A

t t=

C

B A

A

t t

tt

=

=2

(D) 2 2B A

t t=For-2015 (IES, GATE & PSUs) Page 17 of 240 Rev.0


18/240

n e In a sand castin rocess a s rue of 10 mm basediameter and 250 mm height leads to a runner

The volume flow rate (in mm3/s) is

(a) 0.8 x 105 (b) 1.1 x 105c 1.7 x 10 2.3 x 10

n e In a sand castin rocess a s rue of 10 mm basediameter and 250 mm height leads to a runner

The mould filling time (in seconds) is

(a) 2.8 (b) 5.78c 7.54 .41

Expressionforchokearea

= 2m

CA mmct 2gH

Wherem=massofthecasting,kg

=Densityofmetal,kg/m3

t= ourin time

c=Efficiencyfactorandisthefunctionofgates stem used

H=Effectiveheadofliquidmetal

Contd

h

= or ottomgatem2

2

=h forpartinglinegatec

m2h

Ch

mh

m

mh

opga e par ng nega e o omga e

IES20092marks

IAS2011Main

Sketch a mould for two hollow components to be

cast. On the diagram, indicate runner, gate, riser,

core, cope, sprue, pouring basin, sprue well, drag,

.

[10Marks]

IES2013

When an alloy solidifies over a range of

temperature, the resulting casting structure is:

(a) Wholly equiaxed

(b) Wholly columnar

d Dendritic

as ng

e ec s

e o ow ngaret ema or e ects,w c are e yto

occurinsandcastin s:

Gasdefects

Shrinkagecavities

Moldingmaterialdefects

Pouringmetaldefects

o s .

as e ects

A condition existing in a casting caused by thetrapping of gas in the molten metal or by mold gasesevolved during the pouring of the casting.

The defects in this category can be classified intoblowholes and pinhole porosity.

Blowholes are s herical or elon ated cavities resent

in the casting on the surface or inside the casting.

hydrogen gas, which gets entrapped during heating of.



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ShellMoulding

The sand is mixed with a thermosetting resin is

(2000C).

s n s e o a out 3.5 mm o san an p ast cmixture adhere to the pattern.

Then the shell is removed from the pattern.

The cope and drag shells are kept in a flask withnecessary backup material and the molten metal ispoured into the mold.

Can produce complex parts.

goo sur ace n s an goo s ze to erance

reduce the need for machinin .

Materials can be cast: CI, Al and Cu alloys.

Shellmouldingprocess

MoldingSandinShellMolding

The molding sand is a mixture of fine grained quartz sand

an pow ere a e te.

Cold coatin and Hot coatin methods are used for

coating the sand grains with bakelite.

Cold coating:quartz sand is poured into the mixer and

en e so u on o pow ere a e e n ace one an

ethyl aldehyde are added. (mixture is 92% quartz sand,

5% bakelite, 3% ethylaldehyde )Contd

Hot coating:the mixture is heated to 150oC 180oC prior

to loading the sand. In the course of sand mixing, the

.

allowed to cool up to 80 90o C. Hot coting gives better

properties to the mixtures than cold method.

van ages

mens ona accuracy.

.

Very thin sections can be cast.

Very small amount of sand is needed.

m a o n s

Small size castin onl .

Highly complicated shapes cannot be obtained.

More sophisticated equipment is needed for handling

the shell moldings.

Applications

Cylinders and cylinder heads for air cooled IC

engines

Automobile transmission parts.

Piston rings



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CeramicShellInvestmentCasting

In ceramic shell investment casting a ceramic shell is

built around a tree assembly by repeatedly dipping a

zircon with binder).

After each dipping and stuccoing is completed, the

assembly is allowed to thoroughly dry before the next

.

IES20092marks

AdvantagesTight dimensional tolerances

. .

Machinin can be reduced or com letel

eliminated

High melting point alloy can be cast, almost any

Almost unlimited intricacy

Limitations

Costly patterns and moulds

Labour costs can be high

Limited size

Applications

Aerospace and rocket components.

Vanes and blades for gas turbines.

Surgical instruments

IES2011

(a) Slurry coating pattern melt outShakeout Stuccocoat ng

(b) Stucco coating Slurry coating Shakeout Patternmelt out

(c) Slurry coating Stucco coating Pattern melt out

Shakeoutd Stucco coatin Shakeout Slurr coatin Pattern

melt out

GATE2006

An expendable pattern is used in

(a) Slush casting

(b) Squeeze casting

(c) Centrifugal casting

GATE2011(PI)

Which of the following casting processes uses

expendable pattern and expendable mould?

(a) Shell mould casting

(b) Investment casting

d Centrifu al castin



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Di d t A li ti


26/240

Disadvantages

High initial mold cost

, ,

Mold life is very limited with highmeltingpoint.

Low melting point metals can be cast

Zinc

Brass

Applications

Pistons/cylinders/rods

Gears

Kitchenware

Statement (I): Mould walls of a permanent mould areep c .

Statement (II): The thicker mould walls retainmax mum eat ncreas ng ow o mo ten meta .

(a) Both Statement (I) and Statement (II) are individuallytrue and Statement (II) is the correct explanation ofStatement (I)

(b) Both Statement (I) and Statement (II) are individuallytrue but Statement (II) is not the correct explanation ofStatement (I)

(d) Statement (I) is false but Statement (II) is true

DieCasting

Molten metal is injected into closed metal dies under

pressures ranging from 100 to 150 MPa.

ressure s ma n a ne ur ng so ca on

After which the dies se arate and the castin is e ectedalong with its attached sprues and runners.

Cores must be simple and retractable and take the

form of moving metal segments

Hotchamber

Hotchambermachinesare

Good for low temperature (approx. 400C)

Faster than cold chamber machines

Cycle times must be short to minimize metalcontamination

Metal starts in a heated c linderA piston forces metal into the die

e p s on re rac s, an raws me a n

Metal: Lead, Tin, Zinc

HotChamber

Coldchambermachines

Castshighmeltingpointmetals(>600C)

Highpressuresused

Meta is eate inaseparatecruci e

Metalisladledintoacoldchamber

Themetalisrapidlyforcedintothemoldbeforeit

cools

, .For-2015 (IES, GATE & PSUs) Page 26 of 240 Rev.0


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Extremel smoothsurfaces 1 m

Excellentdimensionalaccuracy

Rapidproductionrate

Bettermechanicalpropertiescomparedtosandcasting

Minimumfinishin o erations

Thinsectionspossible

Limitations

Highinitialdiecost

Limitedtohighfluiditynonferrousmetals

Partsizeislimited

oros ymay eapro em

Somescra ins rues runners andflash butthiscan

bedirectlyrecycled

Carburettors

utomot ve parts

Bathroom fixtures

Toys

Common metals

oys o a um num, z nc, magnes um, an ea

Also possible with alloys of copper and tin

IES2011

sand casting :

.

2. Smooth surface

3. rong ense me a s ruc ure

Which of these advantages are correct ?

a 1, 2 an 3(b) 1 and 2 only

(c) 2 and 3 only

(d) 1 and 3 only

IES2009

Which of the following are the most suitablematerials for die casting?

(a) Zinc and its alloys

b Co er and its allo s

(c) Aluminium and its alloys

ea an s a oys

JWM 1Assertion A : In die castin method smallthickness can be filled with liquid metal.

casting causes problems.

correctexplanationofA

ot an are n v ua y true ut snott ecorrectexplanationofA

(c) AistruebutRisfalse

(d) AisfalsebutRistrue

IES2005

Which one of the following processes produces acasting when pressure forces the molten metalinto the mould cavity?

(a) Shell moulding (b) Investmentcasting

(c) Die casting (d) Continuous casting

IES2006

In which of the following are metal moulds used?

(a) Greensand mould

(b) Dry sand mould

(d) Loam moulding

IES1995

Assertion A : An a uminium a oy wit 11 % si icon isused for making engine pistons by die casting

.

Reason (R): Aluminium has low density and additionof silicon im roves its fluidit and therefore itscastability.

(a) Both A and R are individually true and R is the correctexplanation of A

(b) Both A and R are individually true but R is not thecorrect exp anation o A

(c) A is true but R is false

(d) A is false but R is trueFor-2015 (IES, GATE & PSUs) Page 27 of 240 Rev.0


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SqueezeCasting

IAS2002 SingleCrystalCasting


32/240

q g

Process:

1. Molten metal is poured into an open face die.

2. A punch is advanced into the die, and to the metal.

.

and die while the part solidifies.4. e punc s re rac e , an e par s noc e ou

with an ejector pin.

Overcomes problems with feeding the die, andproduces near net, highly detailed parts.

a c s as ng rocess w s (Applications)andselectthecorrectanswerusingthecodesgivenbelowtheLists:ListI ListII(CastingProcess) (Applications)

A. Centrifugalcasting 1. Carburetor

B. Squeezecasting 2. PipesC. DieCasting 3. W ee s or

automobiles.

Codes:A B C A B Ca 2 1 b 1

(c) 2 1 3 (d) 4 3 1

1. Prepare a mold so that one end is a heated oven, and.

that the cooling happens over the longest distance.

2. ast meta nto t e mo

3. Solidification will begin at the chill plate. Thesedendrites will grow towards the heated end of thepart as long dendritic crystals. The part is slowlypulled out of the oven, past the chill plate.

4. Remove the solidified part.

Creepandthermalshockresistanceproperties.

2marks

P asterCast ng, ,

additives is pouted over a pattern and allowed to set. Theattern is removed and the mould is baked to remove

excess water. After pouring and solidification, the mould isbroken and the castin is removed.

Advantage: High dimensional accuracy and smooth

surface finish thin sections and intricate detail canproduce.

Limitations:Lowertem erature nonferrous metals onl :

Common metals:Primarily aluminium and copper

PitMoulding

This method is used for very large castings and is done onthe foundry floor.

IES1996

Whichofthefollowingpairsarecorrectlymatched?

1. Pitmoulding ..................Forlargejobs.

2. Investmentmoulding ...Lostwaxprocess.

. gypsum.

a 1,2an 3 1an 2

(c) 1and3 (d) 2and3

LoamMoulding

Moulding loam is generally artificially composed of

common brickclay, and sharp sand.

Loam means mud.

Loam Moulding is restricted to forms which cannot be

.

It is costl .



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For complete oxidation 0.287 m3 oxygen/kg of iron isrequired

The drag lines shows the characteristics of the movementof the ox en stream.

If torch moved too rapidly, the bottom does not getsufficient heat and roduces lar e dra so ver rou h


39/240

required

Due to unoxidized metal blown away the actualrequirement is much less.

Torch ti held verticall or sli htl inclined in thedirection of travel.

. .

Contd

Drag is the amount by which the lower edge of the dragFig positioningofcuttingtorchinoxyfuelgascutting

line trails from the top edge.

Good cut means negligible drag.

Contd

and irregularshapedcut edges.

generated and produces irregular cut.

Contd

Gas cutting is more useful with thick plates.

For thin sheets (less than 3 mm thick) tip size shouldbe small. If small tips are not available then the tip isinclined at an angle of 15 to 20 degrees.

Fig.Recommended torchpositionforcuttingthinsteel

IAS2011Main

Draw a self explanatory sketch of oxyacetylene gas

cutting torch. Briefly explain how cutting is

effected.

20 ar s

Application

Useful only for materials which readily get oxidized

an t e ox es ave ower me t ng po nts t an t e

metals.

Widely used for ferrous materials.

Cannot be used for aluminum, bronze, stainless steel

and like metals since they resist oxidation.

Difficulties

Metal temperature goes beyond lower criticaltemperature and structural transformations occur.

Final microstructure de ends on coolin rate.

ee s w ess an 0.3 car on cause no pro em.

Contd

For high carbon steel material around the cut should

be preheated (about 250 to 300oC) and may post heat

a so necessary.

Cuttin CI is difficult since its meltin tem . is lower

than iron oxide.

If chromium and nickel etc are present in ferrousalloys oxidation and cutting is difficult.

IES1992

The edge of a steel plate cut by oxygen cutting willget hardened when the carbon content is

(a) Less than 0.1 percent

.

(c) More than 0.3 percent

(d) Anywhere between 0.1 to 1.0 percent



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PrincipleofArc

A i d b h d d d h

Work is negative and electrode is positive is reverse

l ( )

ISRO2011


41/240

An arc is generated between cathode and anode when

t ey are touc e to esta s t e ow o current an

then se arated b a small distance.

65% to 75% heat is generated at the anode.

If DC is used and the work is positive (the anode of the

circuit), the condition is known as straight polarity

.

Contd

polarity (RPDC).

SPDC conditions are preferred.

arcwe ng ma nta n a sta e arc an pre erre or

difficult tasks such as overhead welding.

For a stable arc, the gap should be maintained.

Contd

Inarcwelding,penetrationisminimumfor

(a)DCSP

(b)DCRP

(c)AC

(d)DCEN

Manual arc welding is done with shielded (covered)

Baremetal wire used in automatic or semiautomaticmac nes.

Non consumable electrodes (e.g tungsten) is notconsumed by the arc and a separate metal wire is usedas f iller.

There are three modes of metal transfer (globular,spray and shortcircuit).

Threemodesofmetaltransferduringarcwelding MajorForcestakepartinMetalTransfer

grav ty orce

(iii)electromagneticinteraction

(iv)hydrodynamicactionofplasma

JWM

1ssert on : ea s t e meta a e ur ng

single pass of welding.

Reason (R) : Bead material is same as base metal.

(a) Both A and R are individually true and R is thecorrect explanation of A

b Both A and R are individuall true but R is NOT thecorrect explanation of A

(d) A is false but R is true

GATE1993

Ind.c.welding,thestraightpolarity(electrodenegative)resultsin

(a) Lowerpenetration

b Lowerde ositionrate

(c) Lessheatingofworkpiece

ma erwe poo

Arcwelding

equipments

1. Droopers: Constant current welding machines

Good for manual welding

2. Constant voltage machines


Formula Requires a large current (150 to 1000 A), voltage is


42/240

Fig.Machinewithdifferentsettings

Fig.Characteristiccurveofaconstantvoltagearcweldingmachine

1+ =OCV SCC

between 30 and 40 V, actual voltage across the arc

varying from 12 to 30 V.

To initiate a weld, the operator strike the electrode and

start arc.

In arc weldin the arc len th should bee ual to

(a) 4.5 times the rod diameter

3 mes e ro ame er

(c) 1.5 times the rod diameter

(d) Rod diameter

IES2005Considerthefollowingstatements:

1. Inarcwelding,65%to75%heatisgeneratedattheanode.

2. Dutycycleincaseofarcweldingisthecycleof

beginning.

3.

.

Whichofthestatementsgivenabovearecorrect?

,

(c) 2and3 (d) 1and3

IES2001

Inmanualarcwelding,theequipmentshould

havedroopingcharacteristicsinordertomaintain

a o agecons an w enarc eng c anges

b Currentconstantwhenarclen thchan es

(c) Temperatureintheareconstant

(d) Weldpoolredhot

IES2001

Inarcwelding,d.c.reversepolarityisusedtobeargreateradvantagein

(a) Overheadwelding

(c) Edgewelding

(d) Flatweldingofbuttjoints

IES1998

The voltagecurrent characteristics of a dcgenerator for arc welding is a straight linebetween an opencircuit voltage of 80 V and shortcircuit current of 300 A. The generator settings formaximum arc power will be

a 0 V and 1 0 A b 0 V and 00 A

(c) 40 V and 150 A (d) 80 V and 300 A

IAS1999

Opencircuit voltage of 60 V and current of 160Awere the welding conditions for arc welding of acertain class of steel strip of thickness 10 mm. Forarcwelding of 5mm thick strip of the same steel,the welding voltage and current would be

a 60 V and 80 A

(b) 120 V and 160 Ac 0 an 40

(d) 120 V and 40 A



43/240

ConsumableElectrodes

rov es er ma er a s.Consumable electrodes are three kinds:

(a) Bare

Electrodecoatingcharacteristic

1. Provide a protective atmosphere.


44/240

Same composition.

This requires that the electrode be moved toward oraway from the work to maintain the arc andsatisfactory welding conditions.

Contd

(b) Fluxed or lightly coated

(c) Coated or extruded / shielded

,continuous wire (coil).

2. Stabilize the arc.

3. Provide a protective slag coating to accumulateim urities revent oxidation and slow the coolin ofthe weld metal.

. .

5. Add alloying elements.

6. Affect arc penetration

7. Influence the shape of the weld bead.

8. Add additional filler metal.

GATE1994Theelectrodesusedinarcweldingarecoated.Thiscoatingisnotexpectedto

(a) Provideprotectiveatmospheretoweld

b Stabilizetheare

(c) Addalloyingelements

reven se ec ro e romcon am na on

Electrodecoatings

l. Slag Forming Ingredients. asbestos, mica, silica,fluorspar, titanium dioxide, Iron oxide, magnesiumcarbonate, Calcium carbonate and aluminium oxide.

2. Arc Stabilizing Ingredients. or ionizing agents:otassium silicate TiO + ZrO Rutile Mica

Calcium oxide, sodium oxide, magnesium oxide,felds ar (KAI Si O

Contd

3.DeoxidizingIngredients.Cellulose,Calciumcarbonate dolomite starch dextrinwoodflour , , , , ,graphite,aluminium,ferromanganese.

4.BindingMaterialsSodiumsilicate,potassiumsilicate,asbestos.

5.AlloyingConstituentstoImproveStrengthofWeld

6.TiO2andpotassiumcompoundsincreasethemeltingrateofthebasemetalforbetterpenetration.

7.Ironpowderprovideshigherdepositionrate.

Contd

Contd

The slag is then easily chipped.

Coatings are designed to melt more slowly than thefiller wire.

B n ers

AC arc welding used potassium silicate binders.

.

Potassium has a lower ionization otential as com ared

with sodium.


IES2007

The coating material of an arc welding electrode

IES1997

Assertion (A): The electrodes of ac arc welding arecoated ith sodium silicate hereas electrodes used

IES2002

MatchListIwithListIIandselectthecorrectanswer:


45/240

g gcontains which of the following?

1. Deoxidising agent

.

3. Slag forming agentSelect the correct answer using the code given below:

(a) 1, 2 and 3 (b) 1 and 2 only

(c) 2 and 3 only (d) 1 and 3 only

coated with sodium silicate, whereas electrodes usedfor dc arc weldin are coated with otassium silicatebinders.Reason (R): Potassium has a lower ionizationpotent a t anso um.

(a) Both A and R are individually true and R is the correct

(b) Both A and R are individually true but R isnot thecorrect explanation of A

(c) A is true but R is false(d) A is false but R is true

ListI(Ingredients) ListII(Weldingunct ons

A. Silica 1. Arc stabilizer

B. Potassium oxa ate 2. Deoxi izer

C. Ferrosilicon 3. FluxingagentD. Cellulose 4. Gasformingmaterial

Codes:A B C D A B C D

(a) 3 4 2 1 (b) 2 1 3 4

(c) 3 1 2 4 (d) 2 4 3 1

WeldingFlux

Availableinthreeforms

Granular

Electrodewirecoating

Electrodecore

LowH dro enElectrodeThe basic coatings contain large amount of

ca c um car ona e mes one an ca c umfluoride (fluorspar) and produce low hydrogen.

But it can absorb moisture therefore coated lowhydrogen electrodes are backed before use to a

temperature of 200oC to 3000C and stored in anoven at 110oC to 150oC

Other types of electrode release large amount ofhydrogen, which can dissolve in the weld metaland lead to embrittlement or cracking.

IFS2011Whatismeantbylow hydrogenelectrode?

2mar s

Fig.Thepositionofelectrodeforhorizontalwelding

Fig.Positioningofelectrodeforweldinginverticallyupwardposition

e ng

urrenWeldingcurrentdependsupon:thethicknessofthe

weldedmetal,typeofjoint,weldingspeed,positionoftheweld,thethicknessandtypeofthecoatingontheelectrodeanditsworkinglength.

Weldingcurrent,I =k.d,amperes; disdia.(mm)

WeldingVoltage

Thearcvoltagedependsonlyuponthearclength

V=k1+k2l Volts

Wherelisthearclengthinmmandk1andk2arecons an s,

k1=10to12;andk2=2to3

TheminimumArcvolta eis ivenb

Vmin=(20+0.04l) VoltFor-2015 (IES, GATE & PSUs) Page 45 of 240 Rev.0

ArcLength

For good welds, a short arc length is necessary,b

A long arc results in

Large heat loss into atmosphere.


46/240

because:

1. Heat is concentrated.

2. More stable

3. More protective atmosphere.

Contd

Unstable arc.

Weld pool is not protected.

, ,excessive spatter.

Fig.ArcPowerVsArcLength

Arclengthshouldbeequaltothe diameteroftheelectrodesize

Beadwidthshouldbeequaltothreediameteroftheelectrodesize

ATE , onvent ona

The arc lengthvoltage characteristic of a DC arc is given

= ,

and L is arc length in mm. The static voltampere

characteristic of the power source is approximated by a

straight line with a no load voltage of 80 V and a shortcircuit current of 600A. Determine the o timum arc

length for maximum power.

GATE2010(PI)Durin a stead as metal arc weldin with directcurrent electrode positive polarity, the welding current,

voltage and weld speed are 150 A, 30 V and 6 m/min,respectively. A metallic wire electrode of diameter 1.2mm is being fed at a constant rate of 12 m/min. The

ens ty, spec c eat an me t ng temperature o t ewire electrode are 7000 kg/m3, 500 J/kgoC and 1530oC,

o

.and neglect the latent heat of melting. Further, considerthat twothird of the total electrical ower is available formelting of the wire electrode. The melting efficiency (inpercentage) of the wire electrode is

(a) 39.58 (b) 45.25 (c) 49.38 (d) 54.98

GATE2008

In 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 ofthe 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 in

mm/s is closest to(a) 4 (b) 14 (c) 24 (d) 34

GATE2006

In 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/sec. The net heat input (in J/mm) is

(a) 64

b

(c) 110379700

GATE2009 PI

Autogenous gas tungsten arc welding of a steel

plate is carried out with welding current of 500 A,

voltage of 20 V, and weld speed of 20 mm/sec.

to the weld pool as 90%. The heat input per unit

length (in KJ/mm) is

(a) 0.25 (b) 0.35 (c) 0.45 (d) 0.55For-2015 (IES, GATE & PSUs) Page 46 of 240 Rev.0


47/240

Gasshields

An inert gas is blown into the weld zone to drive away

Helium, most expensive, has a better thermal

conductivity, is useful for thicker sheets, copper and

CarbonArcwelding

Arc is produced between a carbon electrode and the


48/240

ot er atmosp er c gases.

, , ,

a mixture of the above gases.

Argon ionizes easily requiring smaller arc voltages.It is

good for welding thin sheets.

Contd

, .

The arc in carbon dioxide shielding gas is unstable,

least expensive, deoxidizers needed. It is a heavy gas and therefore covers the weld zone

very we .

wor .

.

No pressure

With or without filler metal

May be used in "twin arc method", that is, between

two carbon (graphite) electrodes.

Assertion A : Strai ht olarit is alwa srecommended for Carbonelectrode welding.

.

(a) Both A and R are individually true and R is the

(b) Both A and R are individually true but R is NOT the

correct exp anat on o(c) A is true but R is false


TungstenInertGaswelding(TIG)

Arc is established between a nonconsumabletungsten electrode and the workpiece.

Tungsten is alloyed with thorium or zirconium forbetter currentcarrying and electronemissioncharacteristics.

Arc len th is constant arc is stable and eas to

maintain.

.

Contd

Very clean welds.

me a s an a oys can e we e . , g a so

Strai ht olarit is used.

Weld voltage 20 to 40 V and weld current 125 A for

RPDC to 1000 A for SPDC.

Shielded Gas: Argon

Torch is water or air cooled.

Fig.TIG

GATE2011

usednon consumableelectrode?

a asmeta arcwe ng

(b)Submergedarcwelding

(c)Gastungstenarcwelding

d Fluxcoatedarcweldin

In an inert as weldin rocess the commonl usedgas is

(b) Oxygen

c e um or rgon

(d) Krypton


ISRO2009Following gases are used in tungsten inert

GATE2002Whichofthefollowingarcweldingprocessesdoesnot use consumable electrodes?

IES1994

Whichoneofthefollowingweldingprocessesuses non consumable electrodes?


49/240

Following gases are used in tungsten inertgas we ing

a CO and H2 2

(b) Argon and neon(c) Argon and helium

d Helium and neon

notuseconsumableelectrodes?

(a) GMAW

b GTAW

(c) SubmergedArcWelding

oneo ese

usesnon consumableelectrodes?

(a) TIGwelding

(c) Manual

arc

welding(d) Submergedarcwelding.

IES2000

Whichoneofthefollowingstatementsiscorrect?

a Nofluxisusedin asweldin ofmildsteel

(b) Boraxisthecommonlyusedfluxcoatingon

(c) Laserbeamweldingemploysavacuumchamber

an

us

avo s

use

o

a

s e ng

me o(d) ACcanbeusedforGTAWprocess

IES2013Statement I :Non consumable electrodes, used in arc

welding are made of high melting point temperaturematerials, even then the len th of electrode oes ondecreasing with passage of time.

and melts on the weld material to form a strong flux.

a o a emen an a emen are n v ua y true and Statement (II) is the correct explanation of

a emen(b) Both Statement (I) and Statement (II) are individuallytrue ut tatement s not t e correct exp anat on oStatement (I)

(c) Statement (I) is true but Statement (II) is false


GasMetalArcWelding(GMAW)orMIG

Aconsumable electrode in a gas shield.

Arc is between workpiece and an automatically fedbarewire electrode.

Ar on helium and mixtures of the two can be used.

Any metal can be welded but are used primarily with .

When welding steel, some O2or CO2 is usually addedo mprove e arc s a y an re uce we spa er.

Contd

Fast and economical.

A reversepolarity dc arc is generally used becauseof its deep penetration, spray transfer, and abilityto produce smooth welds with good profile.

Fig.MIG

IES2007

InMIGwelding,themetalistransferredintotheformofwhichoneofthefollowing?

(a) Afinesprayofmetal

(c) Weldpool

(d) Molecules



50/240


51/240

ResistanceWelding

Both heat and pressure are used.

They are not officially classified as solidstate welding

by the American Welding Society.


52/240

By SKMondal

Heat is generated by the electrical resistance of thework pieces and the interface between them.

Pressure is supplied externally and is varied

throughout the weld cycle. Due to pressure, a lower temperature needed than

ox fuel or arc weldin .

Contd

Very rapid and economical.

Extremely well suited to automated manufacturing.

, , .

Contd

Overall resistance very low.

Very highcurrent (up to 100,000 A)

Very lowvoltage 0.5 to 10 V is used.

FIG.Thefundamentalresistanceweldingcircuit

Fi . The desired tem erature Fig. Typical current and

distribution across theelectrodes and the work

pressure cycle for resistance

welding. The cycle includesfor in and ost heatin

welding. operations. Fig. The arrangement of the electrodes and the work in spotwelding, showing design for replaceableelectrode tips.

IES2007

What is the principle of resistance welding?

Indicate where the resistance is maximum in spot

welding operation.

2mar s

Advantages

1. Very rapid.

2. Fully automation possible.

3. onserve ma er a no er me a , s e ng gases, or

flux is required.

4. Skilled operators are not required.

5.Dissimilar metals can be easily joined.

6. High reliability and High reproducibility.

Limitations

1. High initial cost.

2. Limitations to the type of joints (mostly lapjoints).

3. e ma n enance personne1 are requ re

. s ecial surface treatment needed.


Application

The resistance welding processes are among the

Differenttypes

1. Resistance spot welding

Resistancespotwelding

The process description given so far is called resistancespot welding (RSW) or simply spot welding.


53/240

joining.2. Resistance seam welding

3. ro ec onwe ng

. U set weldin

5. Flash welding

6. Percussion welding

This is essentially done to join two sheetmetal jobs ina lap joint, forming a small nugget at the interface ofthe two plates.

HeatinputandEfficiencyCalculations

Contd

Electric Resistance Welding

oules law a licable

Q = I2 Rt, Joules

IES2003

Inresistancewelding,heatisgeneratedduetotheresistancebetween

(a) Electrodeandworkpiece

(c) Twodissimilarmetalsbeingincontact

(d) Inter

atomic

forces

IES2001

Themaximumheatinresistanceweldingisatthe

a Ti ofthe ositiveelectrode

(b) Tipofthenegativeelectrode

c opsur aceo ep a ea e meo e ec r ccontactwiththeelectrode

(d) InterfacebetweenthetwoplatesbeingJoined

GATE2007

Two metallic sheets, each of 2.0 mm thickness, are welded in a la ointconfiguration by resistance spot welding at a welding current of 10 kAand welding time of 10 millisecond. A spherical fusion zone extendingup to the full thickness of each sheet is formed. The properties of the

ambient temperature = 293 Kmelting temperature = 1793 Ka en ea o us on = 300 g

density = 7000 kg/m3

specific heat = 800 J/kg KAssume:(i) Contact resistance along sheetsheet interface is 500 microohm and

along electrodesheet interface is zero;(ii) No conductive heat loss through the bulk sheet materials; and(iii) The completeweld 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

GATE2009

(PI)

Linked

S1

Resistance s ot weldin of two steel sheets is carried out inlap joint configuration by using a welding current of 3 kA anda weld time of 0.2 S. A molten weld nugget of volume 20 mm3

is obtained. The effective contact resistance is 200 (microohms). The material properties of steel are given as:(i) latent heat of melting: 1400 kJ/kg, (ii) density: 8000kg/m3, (iii) melting temperature: 1520oC, (iv) specific heat:0.5 J/ goC. T e am ient temperature is 20oC.

Heat (in Joules) used for producing weld nugget will beassuming 100% eat trans er e iciency

(a) 324 (b) 334 (c) 344 (d) 354



54/240

IAS2003

Assertion (A): Spot welding is adopted to weld twooverlapped metal pieces between two electrode

oints.

Resistanceseamwelding

Weld is made between overlapping sheets of metal.

e seam s a ser es o over app ng spot we s

Welding current is a bit higher than spot welding, tocom ensate short circuit of the ad acent weld.

In other process a continuous seam is produced by


55/240

Reason (R): In this process when current is switchedon, the lapped pieces of metal are heated in arestr cte area.(a) Both A and R are individually true and R is the correct


(c) A is true but R is false(d) A is false but R is true

e seam s a ser es o over app ng spot we s.

.

except that the electrodes are now in the form ofrotating disks.

Timed pulses of current pass to form the overlapping

we s.

Contd

electrodes with a speed of 1.5 m/min for thin sheet.

Contd

Fig.Resistanceseamwelding

GATE 2012 PIIn resistance seam welding, the electrode is in theor mo a

(a) cylinder

(b) flat plate

c coil of wire

(d) circular disc

Projectionwelding

Limitations of spot welding.

1. Electrode condition must be maintainedcontinually, and only one spot weld at a time.

2. For additional stren th multi le welds needed..

Projection welding (RPW) overcomes above.

Contd

Dimples are embossed on work pieces at the weldlocations and then placed between largeareaelectrodes, and pressure and current applied like spot

welding.

Current flows through the dimples and heats themand ressure causes the dim les to flatten and form a

weld.

Fig.Principleofpro ec onwe ng,(a)priortoapplicationofcurrentandpressure(b)andafterformationof

weldsContd

Projections are pressformed in any shape.

Multiple welds at a time.

No indentation mark on the surface.

Bolts and nuts can be attached to other metal parts.

Upsetwelding

Made butt joint compared to lap joint.

Pieces are held tightly and current is applied.

ue o pressure o n s ge s g y upse an ence s

name.

Useful for joining rods or similar pieces.



56/240

IES2000

Considerthefollowingprocesses:

1. Gaswelding

2 Thermit welding

ElectroSlagWelding

Very effective for weldingthick sections.

Heat is derived from the passage of electrical current

A 65mm deep layer of molten slag, protect and

cleanse the molten metal.

atercoo e copper mo ng p ates con ne t e


57/240

2. Thermit welding

. Arcweldin

4. Resistancewelding

orderoftheirweldingtemperaturesis

, , , , , ,

(c) 4,3,1,2 (d)4,1,3,2

Heat is derived from the passage of electrical current

.

Contd

ater coo e copper mo ng p ates con ne t e

li uid and moved u ward.

Multiple electrodes are used to provide an adequatesupply of filler.

Contd

Applications: Shipbuilding, machine manufacture,

heavy pressure vessels, and the joining of large

.

Slow cooling produces a coarse grain structure.

Large HAZ.

Contd

IAS2003

Whichoneofthefollowingisnotanelectricresistancemethodofwelding?

(a) Electroslagwelding

(c) Seamwelding

(d) Flash

welding

IAS2000

Considerthefollowingweldingprocesses:

1. TIGweldin 2. Submer edarcweldin

3. Electroslagwelding4. Thermit welding

c o esewe ngprocessesareuse orwe ngthickpiecesofmetals?

(a) 1,2and3 (b) 1,2and4

(c) 1,3and4 (d) 2,3and4

ElectronBeam

Welding

A beam of electrons is magnetically focused on the

wor p ece n a vacuum c am er.

.

Allows precise beam control and deep weld

penetration.

No shield gas (vacuum chamber used)


IES2004

Assertion (A): In electron beam welding process,vacuum is an essential process parameter

Reason (R): Vacuum provides a highly efficient

IES2002

Inwhichoneofthefollowingweldingtechniquesisvacuumenvironmentrequired?

(a) Ultrasonic welding

IES1993

Electronbeamweldingcanbecarriedoutin

a O enair

(b) A hi ldi i


58/240

Reason (R): Vacuum provides a highly efficientshield on weld zone


correct explanation of A(b) Both A and R are individually true but R isnotthecorrect explanation of A



(a) Ultrasonicwelding

(c) Plasmaarcwelding

(d) Electronbeamwelding

(b) Ashieldinggasenvironment

c pressur ze ner gasc a m e r

(d) Vacuum

IAS2004

WhichoneofthefollowingweldingprocessesconsistsofsmallerHeatAffectedZone(HAZ)?

(a) Arcwelding (b) Electronbeamwelding

LaserBeamWelding

Used a focused laser beam provides power intensities

n excess o 10 cm

of vaporized metal with a surrounding liquid pool.

Depthtowidth ratio greater than 4: 1.

Contd

Very thin HAZ and little thermal distortion.

Filler metal and inert gas shield may or may not used.

Deep penetration.

o vacuum nee e .

.

Contd

Heat input is very low, often in the range 0.1 to 10 J.

Adopted by the electronics industry.

Possible to weld wires without removing the

.

Contd

IES2007

Considerthefollowingstatementsinrespectofthelaserbeamwelding:

1. Itcan euse orwe inganymeta ort eircombinationsbecauseofveryhightemperatureofthe

.

2. Heataffectedzoneisverylargebecauseofquickheatin .

3. Highvacuumisrequiredtocarrytheprocess.

Whichofthestatements ivenaboveis arecorrect?(a) 1and2only (b) 2and3only

,

IES2006

Whichoneofthefollowingweldingprocessesconsistsofminimumheataffectedzone(HAZ)?

(a) ShieldedMetalArcWelding(SMAW)

(c) UltrasonicWelding(USW)

(d) MetalInertGasWelding(MIG)


GATE2012(PI)

Which of the following welding processes results inthe smallest heat affected zone?

(a) Shielded metal arc welding

IAS2007

Consider the following welding processes:

1. Arc weldin 2. MIG weldin

3 Laser beam welding 4 Submerged arc

IAS1999Match List I (Shielding method) with List II (Weldingprocess) and select the correct answer using the codesgiven below the lists:

List I List II


59/240

(a) Shielded metal arc welding

(c) Laser beam welding

(d) Thermit welding

3. Laser beam welding 4. Submerged arc

Select the correct sequence in increasing order of Heata ec e zone us ng e co e

given below:

(a) 12 3 4 (b) 14 2 3

(c 2 1 (d 2 1

A. Flux coating 1. Gas metal arc weldingB. F ux granu es 2. Su merge arc we ngC. CO2 3. Shielded metal arc welding

. .5. Electron beam welding

Codes: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

ForgeWelding

Blacksmith do this.

Borax is used as a flux.

e en s o e o ne were en over appe on e

anvil and hammered to the degree necessary to

produce an acceptable weld.

Quality depends on the skill of the worker and not

use y n ustry.

FrictionWelding

Heat is obtained by the friction between the ends of

t e two parts to e o ne .

axially aligned and pressed tightly against it.

Friction raises the temperature of both the ends. Then

rotation is stopped abruptly and the pressure is

ncrease o o n.

Contd

Machine is similar to a centre lathe.

Power requirements 25 kVA to 175 kVA.

The axial pressure depends on the strength and

hardness of the metals being joined.

MPa for alloy steels.

Contd

Very efficient.

Wide variety of metals or combinations of metals canbe oined such as aluminium to steel.

Grain size is refined

.

Only round bars or tubes of the same size, orconnect ng ars or tu es to at sur aces can o n.

One of the components must be ductile.Friction welding is a solid state welding.

permit cleaning of the surfaces by a burnishing action.Contd

Figfrictionweldingprocess

GATE2007

Whichoneofthefollowingisasolidstatejoining

process

(b) Resistancespotwelding

(c) Friction

welding(d) submergedarcwelding



60/240

Typically the detonation velocity should not exceed120% of the sonic velocit in the metal.

High velocity explosives, 45727620 m/s.TNTRDXPETN ompos on Composition C4

Advantages,

Can bond many dissimilar, normally unweldablemetals

The lack of heating preserves metal treatment


61/240

Contd

Composition C4Datasheet Primacord

Medium velocity explosives, 15244572 m/s

Ammonium nitrate Ammonium perchlorate

NitroguonidineD namitesdiluted PETN

Contd

The lack of heating preserves metal treatment

e process s compact, porta e, an easy to conta n

InexpensiveNo need for surface preparation

Contd

Disadvantages,

The metals must have high enough impact resistance,and ductility (at least 5%)

The cladding plate cannot be too large.

o se an as can requ re wor er pro ec on, vacuumchambers, buried in sand/water.

Contd

Typicalapplications:

Verylargeplatescanbecladded.

Joinsdissimilarmetals.

(titaniumtosteel,Altosteel,AltoCuetc.)

Jointube

to

tube

sheets

of

large

heat

exchangers.

Contd

GATE1992

Inanexplosiveweldingprocess,the..(maximum/minimum)velocityofimpactisfixedbythevelocityofsoundinthe(flyer/target)platematerial

(a) Maximum;target

b Minimum tar et

(c) Maximum;flyer

n mum; yer

IES2011 S1ContdMatchListIwithListIIandselectthecorrectanswerusingthecodegivenbelowthelists:

ListI ListII

A.Laserbeam 1.Canbeappliedforweldingorrefractorymetalswelding likeniobium,tantalum,molybdenumandtungsten.

B.Electron 2.Asoundandcleanweldedjointiscreatedduetobeamwelding rubbingoftwopartsagainsteachotherwith

adequatespeedandpressureproducingintenseheat.

C.Ultrasonic 3.Cleanheatsourcecreatedmuchawayfromjob,a

,highvacuum.

.welding

. ,focalspot,novacuumchamberisrequired.

IES2011

FromS1

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



62/240

Metal Arc Welding, Gas tungsten Arc Welding, and

Diffusion Bonding processes. Brazin and Solderin

BrazingandSoldering raz ng s e o n ng o me a s roug e use o ea

and a filler metal whose melting temperature is above450C; but below the melting point of the metals being

joined.Comparisonwith welding and the brazing process


63/240

g p

[15Marks]

Brazin andSolderin Comparisonwith welding and the brazing process1. e compos t on o t e raz ng a oy s s gn cant y

different from that of the base metal.

.than that of the base metal.

3. Themelting pointof the brazing alloy is lower than thato t e ase meta , so t e ase meta is not me te .

4. Capillary action or capillary attraction draws the,

gravity.

advanta es:

1. All metals can be joined.

2. Suited for dissimilar metals.

3. Quick and economical.

4. Less defects.

.

Contd

Brazingmetalsaretypicallyalloyssuchas,

Brazingbrass(60%Cu,40%Zn)

Manganesebronze

Coppersilicon

Silveralloys(with/withoutphosphorous)

Copperphosphorous

Contd

Extremely clean surface needed.

Fluxes used are combinations of borax, boric acid,

c or es, uor es, e ra ora es an o er we ng

agents.

Contd

A popular composition is 75% borax and 25% boric

acid.

o um cyan e s use n raz ng tungsten tocopper.

.


GATE2005Thestrengthofabrazedjoint

(a) Decreaseswithincreaseingapbetweenthetwojoiningsurfaces

b I i h i i b h

IES2006

Whichoneofthefollowingisnotafusionweldingprocess?

(a) Gaswelding

ISRO2010Which is not correct statement about the function offlux in brazing

a To avoid thermal distortion and crackin

(b) To dissolve surface oxide coatings which have formed


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b Increaseswithincreasein a betweenthetwojoiningsurfaces

joiningsurfacesbeyondwhichitincreases

ncreasesup ocer a ngap e ween e wojoiningsurfacesbeyondwhichitdecreases

(c) Brazing

(d) Resistancewelding

g

(c) To prevent oxides from forming during the brazingoperat on on ot t e ase meta an t e raz ngmaterial

(d) To facilitate the wetting process by reducing theviscosity of the melt

BrazeWelding

Capillary action is not required.

Edge preparation needed.

an o n cas ron.

Contd

Done with an oxyacetylene torch.

Fig.BrazeWelding

Soldering

By definition,solderingis a brazing type of operation

w ere t e er meta as a me t ng temperature

below 0C.

Strength of the filler metal is low.

Soldering is used for a neat leakproof jointor a low

resistance electrical joint.

ot su ta e or g temp. app cat on.

Contd

Effective soldering generally involves six important

(1) Design of an acceptable solder joint,

(2) Selection of the correct solder for the job,

(3) Selection of the proper type of flux,

(4) Cleaning the surfaces to be joined,

, ,allow the molten solder to fill the joint by capillary

,(6) Removal of the flux residue, if necessary.

o er

e a sMost solders are alloys of lead and tin.

Three commonly used alloys contain 60, 50, and 40%

.

Contd

o erF ux

mmon um c or e or ros n or so er ng t n

galvanized iron

Some fluxes are corrosive and should be removed after

use



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IES1992

Weld spatter occurs due to any of the followingexcept

(a) High welding current

JWM2010Assertion (A) : Spatter is one of the welding defects.

Reason (R) : In submerged arc welding process,there is no s atter of molten metal.


IES1998

An arc welded joint is shown in the above figure.The part labelled 'B' in the figure is known as

(a) Weld preparation


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(c) Arc

(d) Wrong polarity

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

correct exp anat on o



(c) Reinforcement

(d) Slag

IES2004

Assertion (A): A sound welded joint should not onlybe strong enough but should also exhibits a good

Reason (R): Welding process is used for fabricating

(a) Both A and R are individually true and R is the correctex lanation of A




IAS2003

Toolmaterialnotsuitedtoresistanceweldingis

(a) Aluminium oxide (b) Stellite

GATE1996Preheatingbeforeweldingisdoneto

(a) Makethesteelsofter

(b) Bumawayoil,grease,etc,fromtheplatesurface

(d) Preventplatedistortion

IES2011

1.Carbonequivalent

2.Heatinput

3.Effectivethickness

3.Hydrogencontentinweldpool

,

(b)1,2and4only

(c)2,3and4only

(d)1,2,3and4

GATE2001

Two 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 Ad ustin the duration of current

(c) Changing the electrode size

ang ng e e ec ro e coa ng

(a) Wrong electrode, faulty preheating and metal

(b) Faulty welds, faulty sequence and rigid joints

(c) Wrong speed, current improperly adjusted and faultypreparation

(d) Uneven heat, improper sequence and deposited

metal shrinks


Affected Zone?

.

2.Notchtoughness

H d b i l

welding process, the work material undergoes

(b) neither melting nor microstructural changes

( ) b h l i d i l h f

Statement (I): H dro en induced crackin occurs in the

heat effected zone adjacent to fusion zone andclassified as solid state cracking

Statement (II):Hydrogen from burning of flux coatingpenetrates martensitic micro cracks preventing healing


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3.Hydrogenembrittlement

4.

Stress

corrosion

cracking(a)1,2and3only

,

(c)2,3and4only

(d)1,2,3and4

(c) both melting and microstructural changes aftersolidification

(d) melting and retains the original microstructure aftersolidification

.

(a) Both Statement (I) and Statement (II) are individually

Statement (I)

(b) Both Statement (I) and Statement (II) are individualltrue but Statement (II) is not the correct explanation ofStatement (I)

(c) Statement (I) is true but Statement (II) is false




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urn ng

onapart.

rea ng

threads.


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T rea ng ,

thepitchofthescrewthreadtobecut.

cutbetothreadscrewtheofPitch

LLss

P=

=

cutbetothreadscrewtheofstartofNumber

screwleadtheofPitchL

=

=

screwleadtheofstartofNumberLz =tra ngearcarr agetosp n eorat ogear Lscg =

on a lathe having a lead screw with a double startthread of itch mm. The ratio of s eeds betweenthe spindle and lead screw for this operation is

(c) 1: 4 (d) 4: 1

,

a lathe. The lead screw has a pitch of 6 mm. If thes indle s eed is 60 r m then the s eed of the leadscrew will be

(c) 120 rpm (d) 180 rpm

. shape).

ar ng o ng roov ng .

a formed cut, a deep cut will cut off the unsupportedart.


r ng or ng

end to create an internal feature.

nur ng

visuallyattractive diamondshaped (crisscross)attern is cut or rolled into metal.

This pattern allows human hands or fingers to get a

p nn ng

shaped over mandrels (also called forms) while mountedon a s innin lathe b the a lication of levered force

with various tools.


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provided by the originallysmooth metal surface.

ISRO2007

Spinning operation is carried out on

(a) Hydraulic press

(b) Mechanical press

(c) Latheng mac ne

Reaming

A reamer enters the workpiece axially through the end

tool. Reaming removes a minimal amount of material

more accurate diameter and a smoother internalfinish.

TappingA tap enters the workpiece axially through the end and

cuts internal threads into an existing hole. Theexisting hole is typically drilled by the required tapdrill size that will accommodate the desired tap.

or o ng ev ces or a es

3 jaw self centering chuck (Disc type jobs being held

4 jaw independently adjusted chuck

Held in a collet (Slender rod like jobs being held incollets )

Mounted on a face plate (Odd shape jobs, being held

in face plate)Mounted on the carriage

Magnetic chuck for thin job

a ec u c sLathe chucks are used to su ort a wider variet ofworkpiece shapes and to permit more operations to beperformed than can be accomplished when the work isheld between centers.

Threejaw, selfcentering chucks are used for work thathas a round or hexagonal cross section.

Each jaw in a fourjaw independent chuck can be movedinward and outward independent of the others by meansof a chuck wrench. Thus they can be used to support a

w e var ety o wor s apes.Combination fourjaw chucks are available in which each

aw can e move n epen ent y or can e movesimultaneously by means of a spiral cam.

3JawChuck 4JawChuck


urn ng ormu a or urn ng

= = 1 2

D Dd DOC mm

,

Average diameter of workpiece2

+= 1 2

avg

D DD mm

+ +L A O, =CTfN


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fN

Metal Removal Rate ( ) = =

2 2

1 2

av g

D DM RR D d fN

Cutting Speed, V =

1D N

,m/ min

Example

How much machining time will be required to reduce

over a length of 100 mm by turning using a carbide

insert. Cutting velocity is 100 m/min and feed rate = 0.2

mm/rev.

of the cutting tool in the direction ofee mot on s 1000 mm, rotat ona

s eed of the work iece is 00 r m andrate of feed is 0.2 mm/revolution, then

e mac n ng me w e

a 10 seconds b 100 seconds

(c) 5 minutes (d) 10 minutes

diameter, if the spindle speed is 80 r.p.m. and crossfeed is 0. mm rev is

(a) 1.5 minutes (b) 3.0 minutes

c 5.4 m nutes .5 m nutes

ommon ata

faced of 0.1 mm/rev with a depth of cut of 1 mm. Thefacin o eration is undertaken at a constant cuttinspeed of 90 m/min in a CNC lathe. The maintan ential cuttin force is 200 N.

Assuming approach and overtravel of the cutting,

(a) 2.93 (b) 5.86 (c) 6.66 (d) 13.33

,rod is being reduced in diameter to 115 mm byturnin on a lathe. The s indle rotates at N = 00rpm and the tool is travelling at an axial speed of200 mm min. The time taken for cuttin is iven b

(a) 30 s (b) 36 s

c 1 m nute 45 s

lathe at 50 m/min. cutting speed 0.8 mm/rev feedand 1. mm de th of cut. What is the rate of metalremoval?

(b) 60,000 mm3/min

(c) 20,000 mm3/min

(d) Can not be calculated with the given data


urn ng aperson a es

Usingacompoundslide,

Usingformtools,

Offsetting the tailstock and

Limited movement of the compound slide

Feeding is by hand and is nonuniform. This isresponsible for lowproductivity and poor surfacefinish.

Can be em lo ed for turnin short internal andexternal tapers with a large angle of (steep) taper

UsingaCompoundSlide contd..

dDtan

=

l2angletaperHalf=

stockofDiameterD =


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Offsettingthetailstock,and

Usingtaperturningattachment.

external tapers with a large angle of (steep) taper.diametersmallerd =

tapertheoflengthl=

,

swiveling the compound rest is preferred for:

(b) Long jobs with steep taper angles

(c) Short jobs with small taper angles

(d) Short jobs with steep taper angles

xamp e

be set up to turn taper on the workpiece having alen th of 200 mm lar er diameter mm and thesmaller 30 mm.

se ng e a s oc

this method.o

) over long lengths.

y o sett ng t e ta stoc , t e ax s o rotat on o t e ois inclined by the half angle of taper.

se ng e a s oc Contd..

( )tanLhor

dDLh =

=

2l

preferredfor

(b) Smalltapers

(c) Longslendertapers

(d) Steeptapers

on full length of a job 300 mm long which is to haveits two diameters at 0 mm and 8 mm res ectivelis

(c) 25 mm (d) 44 mm



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er ca orp ar ype

Gangdrill

MultiSpindledrill

r ng pera ons Chip formationof a drill


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p

NumericalControldrill

DrillThe twist drill does most of the cutting with the tip ofthe bit.

There are flutes

up from the

the top of the

are cast off.

r

The helical f lute in a twist drill provides the necessary

1. earance ang e or t e cutt ng e ge

2. Rake angle for the cutting edge

3. Space for the chip to come out during drilling

. Guidance for the drill to enter into the work iece.

Which of the statements given above are correct?a 1 an 2 2 an 3

(c) 3 and 4 (d) 1 and 4

1. Improve the stiffness

2. ave a too mater a

3. Provide space for chip removal

4. Provide rake angle for the cutting edge

Select the correct answer usin the codes iven below:

Codes:

a 1 an 2 2 an 3(c) 3 and 4 (d) 1 and 4

r

parallel to the drill axis. At the periphery of the drill, it is

equivalent to the helix angle.

e p c earance ang e s e ang e orme y e por on o

the flank adjacent to the land and a plane at right angles to

the drill axis measured at the periphery of the drill.

ea o e e x s e s ance measure para e o e raxis, between corresponding point on the leading edge of the

land in one complete revolution.

r

r s zes are yp ca y measure across e r po n s w

a micrometer

Most widely used material is High Speed Steel

The drill blanks are made by forging and then are twisted to

.

and hardened before the final grinding of the geometry.

Deep hole drilling requires special precautions to take care of

the removal of large volume of chips.For-2015 (IES, GATE & PSUs) Page 81 of 240 Rev.0

(a) Increases from centre to periphery

ecreases rom centre to per p ery

(c) Remains constant

(d) Is irrelevant to the drilling operation

(a) Varies from minimum near the dead centre to a

(b) Is maximum at the dead centre and zero at theper p ery

(c) Is constant at every point of the cutting edge

o n ng e The point angle is selected to suit the hardness and brittleness of

.

Harder materials have higher point angles, soft materials havelower oint an les.

An increase in the drill point angle leads to an increase in thethrust force and a decrease in the torque due to increase of theorthogonal rake angle.

This angle (half) refers to side cutting edge angle of a single point


82/240

y p g g

(d) Is a function of the size of the chisel edge. . Standard Point Angle is 118

It is 116to 118for medium hard steel and cast iron

It is 125 for hardened steel

It is 1 0 to 1 0 for brass and bronze

It is only 60 for wood and plastics

e x ng eHelix angle is the angle between the leading edge of the

land and the axis of the drill. Sometimes it is also calledas spiral angle.

The helix results in a positive cutting rake

point cutting tool.

Large helix : 45 to 60 suitable for deep holes and softerwor mater a s

Small helix : for harder / stronger materials

Zero helix : spade drills for high production drillingmicrodrilling and hard work materials

have

(c) Small point angle (d) No lip

(a) 35o

0

(c) 90o

(d) 5o

holes in

(c) Cast steel (d) Carbon steel

IFS2011

Discuss deephole drilling keeping in mind speed and

feed, mentioning the technique of applying coolant.

[5marks]

twistdrill.DN

m n1000

m=


r ng me

L, m n

fN=

n r ng

23, / min

DMRR fN mm

=

xamp e

o e w 40mm ame er an 50mm ep s o

be drilled in mild steel component. The cutting

speed can be taken as 65 m/min and the feed rate as

0.25 mm/rev. Calculate the machining time and the


83/240

ma er a remova ra e.

D

=2tan

f

s n2

ncut c p t c ness t

D

=

( )2sin

Widthof cut b

=

1tan

( ) tansin

rOrthogonal rakeangle

=

plate with the drill rotating at 300 r.p.m. andmovin at a feed rate of 0.2 mm revolution is

(a) 10 sec (b) 20 sec

c 0 sec 100 sec

in a steel plate of 20 mm thickness. Drill spindles eed is 00 r m feed 0.2 mm rev and drill ointangle is 120. Assuming drill over travel of 2 mm, the

(a) 4 seconds (b) 25 seconds

c 100 secon s 110 secon s

n a s ng e pass r ng operat on, a t roug o e o

1 mm diameter is to be drilled in a steel late of 0

mm thickness. Drill spindle speed is 500 rpm, feed

is 0.2 mm/rev and drill point angle is 118. Assuming

2 mm c earance a approac an ex , e o a r

time (in seconds) is

(a) 35.1 (b) 32.4

(c) 31.2 (d) 30.1

at a speed of 3.9 m/min by single start squarethreads of 6 mm itch and 0 mm diameter. Thespeed of the screw

(b) Is 180 rpm

(c) Is 130 rpm

(d) Cannot be determined as the data is insufficient

for a sixspeed drilling machine using drills ofdiameter 6.2 to 2 mm size and at a cuttin velocitof 18 m/min is

. .

(c) 1.62 (d) 1.82



84/240


85/240

Chuckin ReamerFluted chuckingreamers ave re ebehind the edges of theee as we as eve e

ends. They can cut on

ShellReamerShell reamers often areuse or s zes over 20mm to save cuttingtoolma er a . e s e ,made of HSS for smaller

IFS2011

What is the main difference between rose reamer

and chucking reamer ? Write in short about shell

reamer.


86/240

a por ons o e ee .Their f lutes arere a ve y s o r an ey are intended for light

n s ng cu s.

s zes an w car eedges for larger sizes oror masspro uc on

work.

5mar s

Trepanning Trepanning is a annular groove producing operation

which leaves a solid cylindrical core in the centre. Intrepanning a cutter consisting of one or more cuttingedges placed along the circumference of a circle is usedto produce the annular groove.

TrepanningTool

best accuracy of the hole made?

(c) Broaching (d) Boring

reaming process:

1.

own diameter

2. enera y ra e ang es are not prov e on reamers.

3. Even numbers of teeth are preferred in reamerdesign.

Which of these statements are correct?

(a) 1 and 2 (b) 2 and 3

,

Match ListI with ListII and select the correct answerusing the codes given below the lists:

ListI ListII

A. Reaming 1. Smoothing and squaring surfacearound the hole for ro er seatin

B. Counterboring 2.Sizing and finishing the hole

. oun ers n n 3. n argng e en o e o e

D. Spot facing 4. Making a conical enlargement at the

en o e o eCode:A B C D A B C D

(a) 3 2 4 1 (b) 2 3 1 4

(c) 3 2 1 4 (d) 2 3 4 1

(a) Metal removal rate is high

g sur ace n s s o t a ne .

(c) High form accuracy is obtained

(d) High dimensional accuracy is obtained.

(a) Higher MRR

mprove mens ona to erance

(c) Fine surface finish

(d) Improved positional tolerance



87/240

or ng .

The tool should be set exactly at the same height as the.

sometimes have to be used to prevent the heel of the tool.

or ng ,

depths of cut may be somewhat less than for turning torevent tool vibration and chatter.

In some cases, the boring bar may be made of tungsten' .

The boring tool is a singlepoint cutting tool.

H l lit fi i h b i t i ll hi h l

IES2009


88/240

Hole quality, finish boring can typically achieve holeswithin tolerances of IT9.

Surface finishes better than Ra 1 micron can be achieved.

ormu a or or ng

Average diameter of workpiece += 1 2avgD D

D mm2

+ +L A O, =fN

Metal Removal Rate2 2

= = 1 2

av gM RR D d fN

4 / fN

,

to drilling is to:

(b) Finish the drilled hole

(c) Correct the hole

(d) Enlarge the existing hole

,

single point tool is called

(c) Reaming (d) Internal turning.

,

1. Lathe

2. r ng mac ne

3. Vertical milling machine

4. Horizontal milling machine

a 1 2 b 1

(c) 2 and 4 (d) 1, 2, 3, 4

processes are normally employed for making largediameter holes?

(a) Boring tool

too s or ng an trepann ng assoc at on angun drill

(c) Gun drill and boring tool

(d) Boring tools and trepanning

1. A boring machine is suitable for a job shop.

2. g or ng mac ne s es gne spec a y or o ngmore accurate work when compared to a verticalm ng mac ne.

3. A vertical precision boring machine is suitable forboring holes in cylinder blocks and liners.

(a) 1, 2 and 3 (b) 1 and 2

(c) 2 and 3 (d) 1 and 3.



89/240


90/240


91/240


92/240

ean s o m ngcu ers ngsaworpar ng oo n m ngcu ersor n m s


93/240

acem ngcu ers seo ormre eve cutters m ng Toolformcutters

s o cu er ear ee m ngcu ers p ne s a cu ers


ra em ng ,

mounted with a desired distance between them sothat both sides of a work iece can be milled

simultaneously. This set up is called.

(c) String milling (d) Side milling.

angm ng


94/240

IAS2009Main

With a sketch, explain the principle of working

and variations of bedtype milling machine.

[9marks]

(a) Milling process for generating hexagonal surfaces

rocess o cutt ng gears

(c) Process in which two or more cutters are usedsimultaneously

(d) Milling operation combined with turning

,

milling operations is employed?

(b) Bores

(c) Grooves

(d) Steps on prismatic parts

urn ng yrotarytoo s m ngcutters n ex ng mp eor a n n ex ng

carried out using any of the indexing plates incon unction with the worm.



95/240

(Manufacturing Processes) (Condition)

n s turn ng 1. ac as e m nator

(B) Forming 2. Zero rake

(C) Thread cutting 3. Nose radius

D Down millin . Low s eed

Codes:A B C D A B C D

rpm. If the feed per tooth is 0.1 mm, the table speedin mm er minute is

(a) 120 (b) 18

casting, welding, machine tools, material sc

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