Metal Casting Complete PPT With Question Ans 2

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M t l C tiMetal Casting

By S K MondalCompiled by: S K Mondal Made Easy

Sand castingSand casting uses ordinary sand as the primarymould material.The sand grains are mixed with small amounts ofother materials, such as clay and water, to improvemouldability and cohesive strength and are thenmouldability and cohesive strength, and are thenpacked around a pattern that has the shape of thedesired casting.The pattern must be removed before pouring, themold is usually made in two or more pieces.An opening called a sprue hole is cut from the top ofthe mold through the sand and connected to asystem of channels called runners. Contd….Compiled by: S K Mondal Made Easy

The molten metal is poured into the sprue hole, flowsthrough the runners, and enters the mold cavitythrough an opening called a gate.Gravity flow is the most common means ofintroducing 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 bemade for each casting.

Contd…Compiled by: S K Mondal Made Easy Compiled by: S K Mondal Made Easy

Sequential steps in making a sand castingA pattern board is placed between the bottom (drag) and top (cope) halves of a flask, with the bottom side up.

Sand is then packed into the drag half of the mold.

A bottom board is positioned on top of the packed sand, and the mold is turned over, showing the top (cope) half of pattern with sprue and riser pins in place.

The cope half of the mold is then packed with sand. Contd…Compiled by: S K Mondal Made Easy

The mold is opened, the pattern board is drawn(removed), and the runner and gate are cut into thesurface of the sand.

The mold is reassembled with the pattern boardd d l l d h h hremoved, 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 furtherprocessing.

Compiled by: S K Mondal Made Easy

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Compiled by: S K Mondal Made Easy Compiled by: S K Mondal Made Easy

Casting TermsFlask: A moulding flask is one which holds the sand

mould intact. It is made up of wood for temporary

applications or metal for long‐term use.pp g

Drag: Lower moulding flask.

Cope:Upper moulding flask.

Cheek: Intermediate moulding flask used in three‐

piece moulding.Contd…Compiled by: S K Mondal Made Easy

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

madewith some modifications.

Parting line: This is the dividing line between the two

ld fl k h k h d ldmoulding flasks that makes up the sand mould.

Bottom board: This is a board normally made of wood,

which is used at the start of the mould making.

Contd…Compiled by: S K Mondal Made Easy

Moulding sand: The freshly prepared refractory

material used for making the mould cavity. It is a

mixture of silica, clay and moisture in appropriate

proportions.

Backing sand: This is made up of used and burnt

sand.

Core:Used for making hollow cavities in castings.


Pouring basin: A small funnel‐shaped cavity at the top

of the mould into which the molten metal is poured.

Sprue: The passage through which the molten metal

from the pouring basin reaches the mould cavityfrom the pouring basin reaches the mould cavity.

Runner: The passage ways in the parting plane through

which molten metal flow is regulated before they reach

the mould cavity.

Gate: The actual entry point through which molten

metal enters the mould cavity in a controlled rate. Contd…Compiled by: S K Mondal Made Easy

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Chaplet: Chaplets are used to support cores inside the

mould cavity.

Chill: Chills are metallic objects, which are placed in

h ld i h li f ithe mould to increase the cooling rate of castings.

Riser: It is a reservoir of molten metal provided in the

casting so that hot metal can flow back into the mould

cavity when there is a reduction in volume of metal due

to solidificationContd…Compiled by: S K Mondal Made Easy

PaddingTapering of thinner section towards thicker sectionis known as 'padding'.This will require extra material.If padding is not provided, centre line shrinkage orp g p gporosity will result in the thinner section.


IES‐2001

The main purpose of chaplets is

(a) To ensure directional solidification

(b) To provide efficient venting

(c) For aligning the mold boxes

(d) To support the cores

Ans. (d)


IES‐1996Which of the following methods are used forobtaining directional solidification for riser design

1. Suitable placement of chills

2. Suitable placement of chaplets

3. Employing padding

Select the correct answer.

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

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

IES 2007

Which one of the following is the correctstatement?Gate is provided in moulds to(a) Feed the casting at a constant rate(b) Give passage to gases(c) Compensate for shrinkage(d) Avoid cavities

Ans. (a)


GATE‐2009Match the items in Column I and Column II.Column I Column IIP. Metallic Chills 1. Support for the coreQ. Metallic Chaplets 2. Reservoir of the molten metalR. Riser 3. Control cooling of critical

sectionsS. Exothermic Padding 4. Progressive solidification(a) P‐1,Q‐3, R‐2, S‐4 (b) P‐1,Q‐4, R‐2, S‐3(c) P‐3, Q‐4, R‐2, S‐1 (d) P‐4, Q‐1, R‐2, S‐3

Ans. (d)


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GATE‐1992In a green‐sand moulding process, uniform ramming leads to(a) Less chance of gas porosity(b) Uniform flow of molten metal into the mould (b) Uniform flow of molten metal into the mould cavity(c) Greater dimensional stability of the casting(d) Less sand expansion type of casting defect

Ans. (c)


GATE 2011Green sand mould indicates that(a) polymeric mould has been cured(b) mould has been totally dried(c) mould is green in colour( ) g(d) mould contains moisture

Ans. (d)


PatternA pattern is a replica of the object to be made by thecasting process, with some modifications.

Themainmodifications areThe addition of pattern allowancesThe addition of pattern allowances,The provision of core prints, andElimination of fine details, which cannot be obtainedby casting and hence are to be obtained by furtherprocessing


Pattern Allowances1. Shrinkage or contraction allowance

2. Draft or taper allowance

M hi i fi i h ll3. Machining or finish allowance

4. Distortion or camber allowance

5. Rapping allowance


Shrinkage allowanceAll metals shrink when cooling except perhaps

bismuth.

This is because of the inter‐atomic vibrations which

are amplified by an increase in temperature.

The shrinkage allowance is always to be added to the

linear dimensions. Even in case of internal dimensions.


Liquid shrinkage and solid shrinkageLiquid shrinkage refers to the reduction involume when the metal changes from liquid tosolid state at the solidus temperature. To accountfor this, risers are provided in the moulds.

Solid shrinkage is the reduction in volumecaused, when a metal loses temperature in thesolid state. The shrinkage allowance is provided totake care of this reduction.


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Pattern AllowancesCast Iron 10 mm/mBrass, Copper, Aluminium 15 mm/mSteel 20 mm/mZinc, Lead 25 mm/m

In grey cast iron and spheroidal graphite iron, theamount of graphitization controls the actualshrinkage. When graphitization is more, theshrinkage would be less and vice versa.


IES‐1995Which one of the following materials will require

the largest size of riser for the same size of casting?

(a) Aluminium( )

(b) Cast iron

(c) Steel

(d) Copper

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

GATE‐1999

Which of the following materials requires thelargest shrinkage allowance, while making apattern for casting?( ) l(a) Aluminium(b) Brass(c) Cast Iron(d) Plain Carbon Steel

Ans. (d)


IES‐1999In solidification of metal during casting,

compensation for solid contraction is

(a) Provided by the oversize pattern

(b) Achieved by properly placed risers

(c) Obtained by promoting directional

solidification

(d) Made by providing chills

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

GATE‐2001Shrinkage allowance on pattern is provided tocompensate for shrinkage when(a) The temperature of liquid metal drops from

pouring to freezing temperaturepouring to freezing temperature(b) The metal changes from liquid to solid state at

freezing temperature(c) The temperature of solid phase drops from

freezing to room temperature(d) The temperature of metal drops from pouring

to room temperatureAns. (c) Compiled by: S K Mondal Made Easy

GATE‐2004

Gray cast iron blocks 200 x 100 x 10 mm are to becast in sand moulds. Shrinkage allowance forpattern making is 1%. The ratio of the volume of

tt t th t f th ti ill bpattern to that of the casting will be(a) 0.97 (b) 0.99 (c) 1.01 (d) 1.03

Ans. (d)


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GATE‐2008

While cooling, a cubical casting of side 40 mmundergoes 3%, 4% and 5% volume shrinkageduring the liquid state, phase transition and solidt t ti l Th l f t lstate, respectively. The volume of metalcompensated from the riser is(a) 2% (b) 7% (c) 8% (d) 9%

Ans. (b)


GATE 2011A cubic casting of 50 mm side undergoes volumetricsolidification shrinkage and volumetric solidcontraction of 4% and 6% respectively. No riser isused. Assume uniform cooling in all directions. Theside of the cube after solidification and contraction isside of the cube after solidification and contraction is(a) 48.32 mm(b) 49.90 mm(c) 49.94 mm(d) 49.96 mm

Ans. (a)


IAS‐1995Assertion (A): A pattern is made exactly similar to thepart to be cast.Reason (R): Pattern is used to make the mould cavityfor pouring in molten for casting.(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 correctexplanation of A(b) Both A and R are individually true but R is not thecorrect explanation of A(c) A is true but R is false(d) A is false but R is true

Ans. (d)


IAS‐2003Match List I (Material to be cast) with List II(Shrinkage Allowance in mm/m) and select thecorrect answer using the codes given below the lists:List‐I List‐II(Material to Cast) (Shrinkage Allowance in mm/m)(Material to Cast) (Shrinkage Allowance in mm/m)(A) Grey cast iron 1. 7 ‐ 10(B) Brass 2. 15(C) Steel 3. 20(D) Zinc 4. 24 [Ans. (c)]

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


DraftTo reduce the chances of the damage of the mould

cavity at the time of pattern removal, the vertical faces

of the pattern are always tapered from the parting line.

This provision is called draft allowance.

Inner surfaces of the pattern require higher draft than

outer surfaces.

Draft is always provided as an extra metal.

Compiled by: S K Mondal Made Easy DRAFT ALLOWANCECompiled by: S K Mondal Made Easy

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Shake Allowance

At the time of pattern removal, the pattern is rapped

all around the vertical faces to enlarge the mould

cavity slightly to facilitates its removalcavity slightly to facilitates its removal.

It is a negative allowance and is to be applied only to

those dimensions, which are parallel to the parting

plane.


Distortion Allowance A metal when it has just solidified is very weak andtherefore is likely to be distortion prone.

This is particularly so for weaker sections such as longThis is particularly so for weaker sections such as longflat portions, V, U sections or in a complicated castingwhich may have thin and long sections which areconnected to thick sections.

The foundry practice should be to make extramaterial provision for reducing the distortion.


Pattern MaterialsWood patterns are relatively easy to make. Wood is notvery dimensionally stable. Commonly used teak, whitepine and mahogany wood.Metal patterns are more expensive but are moredimensionally stable and more durable Commonly useddimensionally stable and more durable. Commonly usedCI, Brass, aluminium and white metal.Hard plastics, such as urethanes, and are often preferredwith processes that use strong, organically bonded sandsthat tend to stick to other pattern materials.In the full‐mold process, expanded polystyrene (EPS) isused.Investment casting useswax patterns.


The pattern material should beEasily worked, shaped and joined

Light in weight

Strong, hard and durable

Resistant to wear and abrasion

Resistant to corrosion, and to chemical reactions

Dimensionally stable and unaffected by variations in

temperature and humidity.

Available at low cost.Compiled by: S K Mondal Made Easy

IES‐1994Which of the following materials can be used for

making patterns?

1. Aluminium 2. Wax 3. Mercury 4. Lead3 y 4

Select the correct answer using the codes given below:

Codes:

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

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

GATE‐2000

Disposable patterns are made of

(a) Wood

(b) Rubber

(c) Metal

(d) Polystyrene

Ans. (d)


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Types of PatternSingle Piece Pattern

These are inexpensive and the simplest type ofpatterns. As the name indicates, they are made of asingle piece.

Gated PatternGating and runner system are integral with thepattern. This would eliminate the hand cutting ofthe runners and gates and help in improving theproductivity of a moulding.


Types of PatternSplit Pattern or Two Piece PatternThis is the most widely used type of pattern for intricatecastings. When the contour of the casting makes itswithdrawal from the mould difficult, or when the depthof the casting is too high then the pattern is split into twoof the casting is too high, then the pattern is split into twoparts so that one part is in the drag and the other in thecope.


Types of PatternCope and Drag Pattern

These are similar to split patterns. In addition tosplitting the pattern, the cope and drag halves ofthe pattern along with the gating and riser systemsp g g g yare attached separately to the metal or woodenplates along with the alignment pins. They arecalled the cope and drag patterns.


Types of Pattern

Match Plate PatternThe cope and drag patterns along with thegating and the risering are mounted on a singlematching metal or wooden plate on either side.


Types of PatternLoose Piece Pattern

This type of pattern is also used when thecontour of the part is such that withdrawing thepattern from the mould is not possiblepattern from the mould is not possible.


Types of PatternFollow Board Pattern

This type of pattern is adopted for thosecastings where there are some portions, whichare structurally weak and if not supportedproperly are likely to break under the force ofproperly are likely to break under the force oframming.


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IES‐2008

The pattern adopted for those castings where thereare some portions which are structurally weak andare likely to break by the force of ramming arell dcalled:

(a) Loose piece pattern(b) Follow board pattern(c) Skelton pattern(d) Single piece pattern


Types of PatternSweep Pattern

It is used to sweep the complete casting by meansof a plane sweep. These are used for generatinglarge shapes, which are axi‐symmetrical ori ti i t h b ll h dprismatic in nature such as bell‐shaped or

cylindrical.


Types of PatternSkeleton Pattern

A skeleton of the pattern made of strips of woodis used for building the final pattern by packingsand around the skeleton. After packing thesand the desired form is obtained with the helpsand, the desired form is obtained with the helpof a strickle. This type of pattern is usefulgenerally for very large castings, required insmall quantities where large expense oncomplete wooden pattern is not justified.


Cooling Curve


FluidityThe ability of a metal to flow and fill a mold is knownas fluidity.

Pouring TemperatureThe most important controlling factor of fluidity is thepouring temperature or the amount of superheat.p g p pHigher the pouring temperature, the higher the fluidity.Excessive temperatures should be avoided, however. Athigh pouring temperatures, metal‐mold reactions areaccelerated and the fluidity may be so great as to permitpenetration.Penetration is a defect where the metal not only fills themold cavity but also fills the small voids between the sandparticles in a sand mold.


CoreUsed for making cavities and hollow projections.

All sides of core are surrounded by the molten metaland are therefore subjected to much more severeand are therefore subjected to much more severethermal and mechanical conditions and as a result thecore sand should be of higher strength than themoulding sand.


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Desired characteristics of a core

Green Strength: A core made of green sand shouldbe strong enough to retain the shape till it goes forbaking.

h h ld h d d hDry Strength: It should have adequate dry strengthso that when the core is placed in the mould, itshould be able to resist the metal pressure acting onit.Refractoriness: Since in most cases, the core issurrounded all around it is desirable that the corematerial should have higher refractoriness.


Permeability: Gases evolving from the molten metaland generated from the mould may have to gothrough the core to escape out of the mould. Hencecores are required to have higher permeability.

Permeability Number: The rate of flow of air passingth h t d d i d t d d ithrough a standard specimen under a standard pressure istermed as permeability number.The standard permeability test is to measure timetaken by a 2000 cu cm of air at a pressure typically of980 Pa (10 g/cm2), to pass through a standard sandspecimen confined in a specimen tube. The standardspecimen size is 50.8 mm in diameter and a length of50.8 mm. Compiled by: S K Mondal Made Easy

Then, the permeability number, R is obtained by

Where V= volume of air = 2000 cm3

H = height of the sand specimen = 5.08 cmp = air pressure, g/cm2

VHRpAT

=

p p , g/A = cross sectional area of sand specimen = 20.268 cm2

T = time in minutes for the complete air to pass through

Inserting the above standard values into the expression, we get

501.28.

Rp T

=Compiled by: S K Mondal Made Easy

Calculate the permeability number of sand if it takes 1 min 25 s to pass 2000 cm3 of air at a pressure of5 g/cm2 through the standard sample.

25.0 /1min 25 1 417 min

p g cmT s== =1min 25 1.417 min

501.28 70.755 1.417

T s

R

= =

= =×


Collapsibility: At the time of cooling, casting shrinks,

and unless the core has good collapsibility (ability to

decrease in size) it is likely to provide resistance against

shrinkage and thus can cause hot tears.

Friability: The ability to crumble should be a very

important consideration at the time of removal.

Smoothness: Surface of the core should be smooth for

good finish to the casting.

Low Gas EmissionCompiled by: S K Mondal Made Easy

Core SandsUsed clay free silica sand.

Binders used are linseed oil, core oil, resins, dextrin,

molasses, etc.

Core oils are mixtures of linseed, soy, fish and

petroleum oils and coal tar.

The general composition of a core sand mixture could

be core oil (1%) and water (2.5 to 6%).


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Carbon Dioxide MouldingSodium silicate (water glass, SiO2:Na2O) is used as a binder.This is essentially a quick process of core or mouldpreparation.The mould is prepared with a mixture of sodium silicate andsand and then treated with carbon dioxide for two to threeminutes such that a dry compressive strength of over 1.4MPa is arrived.The carbon dioxide is expected to form a weak acid, whichhydrolyses the sodium silicate resulting in amorphous silica,which forms the bond.The introduction of CO2 gas starts the reaction by forminghydrated sodium carbonate (Na2CO3 + H2O).


The compressive strength of the bond increases with

standing time due to dehydration.

Because of the high strength of the bond, the core need not

be provided with any other reinforcements.p y

It does not involve any distortions due to baking and also

better dimensional accuracies are achieved.

The sand mixture does not have good shelf life and

therefore should be used immediately after preparation.


IES‐2002Assertion (A): In CO2 casting process, the mould orcore attains maximum strength.Reason (R): The optimum gassing time of CO2through the mould or core forms Silica Gel whichimparts sufficient strength to the mould or coreimparts sufficient strength to the mould or core.(a) Both A and R are individually true and R is thecorrect explanation of A(b) Both A and R are individually true but R is not thecorrect explanation of A(c) A is true but R is false(d) A is false but R is true

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

Moulding Sand CompositionSand: Ordinary silica Sand (SiO2), zircon, or olivine

sands.

Clay: Acts ss binding agents mixed to the moulding

sands

Kaolinite or fire clay (Al2O3 2SiO2 2H2O), and

Bentonite (Al2O3 4SiO2 H2O nH2O).

Water: Clay is activated by water.


Other AdditivesCereal binder up to 2% increases the strength.

Pitch if used up to 3% would improve the hot

strength.g

Saw dust up to 2% may improve the collapsibility by

slowly burning, and increase the permeability.

Other materials: sea coal, asphalt, fuel oil, graphite,

molasses, iron oxide, etc.Compiled by: S K Mondal Made Easy

Moulding Sand PropertiesPorosity or Permeability: Permeability or porosity ofthe moulding sand is the measure of its ability topermit air to flow through it.Strength: It is defined as the property of holdingt th f d i A ldi d h ld htogether of sand grains. A moulding sand should haveample strength so that the mould does not collapse orget partially destroyed during conveying, turning overor closing.Refractoriness: It is the ability of the moulding sandmixture to withstand the heat of melt without showingany signs of softening or fusion.


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Plasticity: It is the measure of the moulding sand to flow around and over a pattern during ramming and to uniformly fill the flask. Collapsibility: This is the ability of the moulding sand to decrease in volume to some extent under the compressive forces developed by the shrinkage of metal during freezing p y g g gand subsequent cooling. Adhesiveness: This is the property of sand mixture to adhere to another body (here, the moulding flasks). The moulding sand should cling to the sides of the moulding boxes so that it does not fall out when the flasks are lifted and turned over. This property depends on the type and amount of binder used in the sand mix.


Other SandsFacing sand: The small amount of carbonaceousmaterial sprinkled on the inner surface of the moldcavity to give a better surface finish to the castings.Backing sand: It is what constitutes most of therefractory material found in the mould This is maderefractory material found in the mould. This is madeup of used and burnt sand.Green Sand: The molding sand that containsmoisture is termed as green sand. The green sandshould have enough strength so that the constructedmould retains its shape.Dry sand: When the moisture in the moulding sand iscompletely expelled, it is called dry sand.Compiled by: S K Mondal Made Easy

IES‐2008

Small amount of carbonaceous material sprinkledon the inner surface of mould cavity is called(a) Backing sand(b) Facing sand(c) Green sand(d) Dry sand

Ans. (b)


Grain size numberASTM (American Society for Testing and Materials)grain size number, defined as

NWhere N is the number of grains per square inch

-n12Where N is the number of grains per square inchvisible in a prepared specimen at 100X and n is theASTM grain‐size number. Low ASTM numbers mean afew massive grains; high numbers refer to many smallgrains.


IES‐2002

In the grain ‐size determination using standard charts, the relation between the given size number n and the average number of grains 'N' per square inch at a magnification of 100 X isper square inch at a magnification of 100 X is(a) N = 2n

(b) N = 2n‐l

(c) N = 2n + 1

(d) N = 2n + 1Ans. (b)


Casting YieldThe casting yield is the proportion of the actualcasting mass, w, to the mass of metal poured into themould, W, expressed as a percentage.

= ×Casting yield 100wW


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Gating System


Gating SystemPouring basin: A small funnel shaped cavity at thetop of the mould into which the molten metal ispoured.

S Th th h hi h th lt t lSprue: The passage through which the molten metal,from the pouring basin, reaches the mould cavity. Inmany cases it controls the flow of metal into themould.

Runner: The channel through which the moltenmetal is carried from the sprue to the gate.


Ingate: A channel through which the molten metal enters the mould cavity. Vent: Small opening in the mould to facilitate escape of air and gases.


Types of Gate or In‐gateTop gate: Causes turbulence in the mould 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,

higher pouring time, Causes unfavourable temperature

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.Compiled by: S K Mondal Made Easy

IES 2011In light metal casting, runner should be so designed that:

1. It avoids aspiration2. It avoids turbulence3. The path of runner is reduced in area so that

unequal volume of flow through each gateunequal volume of flow through each gatetakes place

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

Ans. (a)


IES 2011Match List –I with List –II and select the correct answer usingthe code given below the lists :

List –I List –II

A. Top gate 1. Heavy and large castings

B. Bottom gate 2. Most widely used and economical

Codes [Ans. (a)]A B C D A B C D

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

g y

C. Parting gate 3. Turbulence

D. Step gate 4. Unfavourable temperature gradient


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IES‐1998A sand casting mouldassembly is shown inthe above figure. Theelements marked Aand B are respectivelyand B are respectively(a) Sprue and riser(b) Ingate and riser(c) Drag and runner(d) Riser and runnerAns. (a)


GATE‐2002The primary purpose of a sprue in a castingmould is to(a)Feed the casting at a rate consistent with the rateof solidificationof solidification

(b)Act as a reservoir for molten metal(c)Feed molten metal from the pouring basin to thegate

(d)Help feed the casting until all solidification takesplace


The goals for the gating system To minimize turbulence to avoid trapping gasses intothe moldTo get enough metal into the mold cavity before themetal starts to solidifyTo avoid shrinkageEstablish the best possible temperature gradient in thesolidifying casting so that the shrinkage if occurs mustbe in the gating system not in the required cast part.Incorporates a system for trapping the non‐metallicinclusions.


IES‐1998Which of the following are the requirements of an ideal gating system?

1. The molten metal should enter the mould cavity with as high a velocity as possible.

2 It should facilitate complete filling of the mould cavity2. It should facilitate complete filling of the mould cavity.3. It should be able to prevent the absorption of air or gases

from the surroundings on the molten metal while flowing through it.Select the correct answer using the codes given below:

(a) 1, 2 and 3 (b) 1 and 2 (c) 2 and 3 (d) 1 and 3Ans. (c)


IES‐2009Consider the following statements:1.The actual entry point through which the molten metal enters the mould cavity is called ingate.2.Bottom gate in case of a mould creates unfavourablegtemperature gradient.3.Sprue in case of a mould is made tapered to avoid air inclusion.Which of the above statements is/are correct?(a) 1 only (b) 1 and 2 (c) 2 and 3 (d) 1 and 3


Types of Gating Systems

The gating systems are of two types:

Pressurized gating systemPressurized gating system

Un‐pressurized gating system


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Pressurized Gating SystemThe total cross sectional area decreases towards themold cavityBack pressure is maintained by the restrictions in themetal flowFlow of liquid (volume) is almost equal from all gatesBack pressure helps in reducing the aspiration as thesprue always runs fullBecause of the restrictions the metal flows at highvelocity leading to more turbulence and chances ofmold erosion.


Un‐Pressurized Gating SystemThe total cross sectional area increases towards the

mold cavity

Restriction only at the bottom of spruey p

Flow of liquid (volume) is different from all gates

Aspiration in the gating system as the system never

runs full

Less turbulence.Compiled by: S K Mondal Made Easy

Sprue DesignSprue: Sprue is the channel through which the moltenmetal is brought into the parting plane where it enters therunners and gates to ultimately reach the mould cavity.The molten metal when moving from the top of the cope tothe parting plane gains in velocity and some low‐pressurep g p g y parea would be created around the metal in the sprue.Since the sand mould is permeable, atmospheric air wouldbe breathed into this low‐pressure area which would thenbe carried to the mould cavity.To eliminate this problem of air aspiration, the sprue istapered to gradually reduce the cross section as it movesaway from the top of the cope as shown in Figure below (b).


The exact tapering can be obtained by the equation of continuity. Denoting the top and choke sections of The sprue by the subscripts’t’ and 'c' respectively, we get

t t c cA V A V= = ct c

t

VA AV


Since the velocities are proportional to the square of the potential heads, as can be derived from Bernoulli's equation,

= ct c

t

hA Ah

Where H = actual sprue heightand ht = h + H


GATE‐2001The height of the down‐sprue is 175 mm and itscross‐sectional area at the base is 200 mm2. Thecross‐sectional area of the horizontal runner isl 2 A i l i di t thalso 200 mm2. Assuming no losses, indicate thecorrect choice for the time (in seconds) required tofill a mould cavity of volume 106 mm3. (Use g = 10m/s2).

(a)2.67 (b)8.45 (c)26.72 (d)84.50Ans. (a)


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GATE‐2007A 200 mm long down sprue has an area of crosssection of 650 mm2 where the pouring basin meets thedown sprue (i.e. at the beginning of the down sprue).A constant head of molten metal is maintained by thepouring basin. The Molten metal flow rate is 6.5 × 105p g 5mm3/s. Considering the end of down sprue to be opento atmosphere and an acceleration due to gravity of104mm/s2, the area of the down sprue in mm2 at its end(avoiding aspiration effect) should be

(a)650.0 (b)350.0 (c)290.7 (d)190.0Contd…Compiled by: S K Mondal Made Easy


Gating ratioGating ratio is defined as: Sprue area: Runner area:

Ingate area.

For high quality steel castings, a gating ratio of 1: 2: 2 or

1: 2: 1.5 will produce castings nearly free from erosion,

will minimize oxidation, and will produce uniform

flow.

A gating ratio of 1: 4: 4 might favour the formation of

oxidation defects.Compiled by: S K Mondal Made Easy

IES‐2003A gating ratio of 1: 2: 4 is used to design the gatingsystem for magnesium alloy casting. This gating ratiorefers to the cross∙ section areas of the various gatingelements as given below:1. Down sprue 2. Runner bar 3. IngatesThe correct sequence of the above elements in theratio 1: 2: 4 is(a) 1, 2 and 3(b) 1,3 and 2(c) 2, 3 and 1(d) 3, 1 an 2

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

IES‐2005

The gating ratio 2: 8: 1 for copper in gating systemdesign refers to the ratio of areas of:(a) Sprue: Runner: Ingate(b) Runner: Ingate: Sprue(c) Runner: Sprue: Ingate(d) Ingate: Runner: Sprue

Ans. (a)


GATE‐2010

In a gating system, the ratio 1:2:4 represents

(a) Sprue base area: runner area: ingate area

(b) Pouring basin area : ingate area : runner area

(c) Sprue base area : ingate area : casting area

(d) Runner area : ingate area : casting area

Ans. (a)


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IAS‐1999Assertion (A): The rate of flow of metal through sprueis NOT a function of the cross‐sectional areas ofsprue, runner and gate.Reason (R): If respective cross‐sectional areas ofsprue, runner and gate are in the ratio of 1: 2: 2, thesystem is known as unpressurised gating systemsystem is known as unpressurised gating system.(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 explanation of A(c) A is true but R is false(d) A is false but R is true


Risers and Riser DesignRisers are added reservoirs designed to feed liquidmetal to the solidifying casting as a means ofcompensating for solidification shrinkage.To perform this function, the risers must solidify afterthe castingthe casting.According to Chvorinov's rule, a good shape for a riserwould be one that has a long freezing time (i.e., a smallsurface area per unit volume).Live risers (also known as hot risers) receive the lasthot metal that enters the mold and generally do so at atime when the metal in the mold cavity has alreadybegun to cool and solidify.Compiled by: S K Mondal Made Easy

IES‐1994Assertion (A): In a mould, a riser is designed and placedso that the riser will solidify after the casting has solidified.Reason (R): A riser is a reservoir of molten metal whichwill supply molten metal where a shrinkage cavity wouldhave occurred.( ) B h A d R i di id ll d R i h(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 explanation of A(c) A is true but R is false(d) A is false but R is true


Chvorinov’s ruleTotal solidification time (ts) = B (V/A) n

where n = 1.5 to 2.0[Where, B = mould constant and is a function of (mould material, casting material, and condition of casting]

n = 2 and triser = 1.25 tcasting

⎛ ⎞ ⎛ ⎞=⎜ ⎟ ⎜ ⎟⎝ ⎠ ⎝ ⎠

2 2

riser casting

V V1.25A A

( )= π

π= π +

2

2

V D H / 4DA DH 2 4

For cylinder of diameter D and height H

or


IES 2011The relationship between total freezing time t,volume of the casting V and its surface area A,according to Chvorinov’s rule is :

( ) Va t kA

⎛ ⎞= ⎜ ⎟⎝ ⎠

Where K is a constant [Ans. (d)]

2

2

( )

( )

( )

AAb t kV

Ac t kV

Vd t kA

⎜ ⎟⎝ ⎠⎛ ⎞= ⎜ ⎟⎝ ⎠

⎛ ⎞= ⎜ ⎟⎝ ⎠

⎛ ⎞= ⎜ ⎟⎝ ⎠


IES‐1998A spherical drop of molten metal of radius 2 mm

was found to solidify in 10 seconds. A similar drop

of radius 4 mmwould solidify inof radius 4 mmwould solidify in

(a) 14.14 seconds

(b) 20 seconds

(c) 28.30 seconds

(d) 40 seconds [Ans. (d)]Compiled by: S K Mondal Made Easy

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GATE‐2003

With a solidification factor of 0.97 x 106 s/m2, thesolidification time (in seconds) for a sphericalcasting of 200 mm diameter is

(a) 539 (b) 1078 (c) 4311 (d) 3233

[Ans. (b)]


IES‐2006According to Chvorinov's equation, the

solidification time of a casting is proportional to:

(a) v2(a) v

(b) v

(c) 1/v

(d) 1/v2

Where, v = volume of casting [Ans. (a)]Compiled by: S K Mondal Made Easy

GATE‐2007

Volume of a cube of side 'l' and volume of a sphere ofradius ‘r’ are equal. Both the cube and the sphere aresolid and of same material. They are being cast. Theti f th lidifi ti ti f th b t thratio of the solidification time of the cube to the same

of the sphere is:

( ) ( ) ( ) ( )3 6 2 2 3 2 44 r 4 r 4 r 4 ra b c d

6 l 6 l 6 l 6 lπ π π π⎛ ⎞ ⎛ ⎞ ⎛ ⎞⎛ ⎞ ⎛ ⎞ ⎛ ⎞ ⎛ ⎞ ⎛ ⎞

⎜ ⎟ ⎜ ⎟ ⎜ ⎟⎜ ⎟ ⎜ ⎟ ⎜ ⎟ ⎜ ⎟ ⎜ ⎟⎝ ⎠ ⎝ ⎠ ⎝ ⎠⎝ ⎠ ⎝ ⎠ ⎝ ⎠ ⎝ ⎠ ⎝ ⎠

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

Conventional Question ESE 2003:

Compare the solidification time of two optimum side – risers of the same volume i h h li d i l h d h i with one has cylindrical shape and other is

parallopiped. [30 Marks]


Modulus MethodIt has been empirically established that if the modulus

of the riser exceeds the modulus of the casting by a

factor of 1.2, the feeding during solidification would be

satisfactory.

MR = 1.2 Mc

Modulus = volume/Surface area

In steel castings, it is generally preferable to choose a

riser with a height‐to‐diameter ratio of 1.Contd…Compiled by: S K Mondal Made Easy

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22

4D Dπ π+4


Conventional Question IES‐2008Calculate the size of a cylindrical riser (height and diameter

equal) necessary to feed a steel slab casting of dimensions

30 x 30 x 6 cm with a side riser casting poured horizontally30 x 30 x 6 cm with a side riser, casting poured horizontally

into the mould.

[Use Modulus Method]

[10 ‐Marks]


Caine’s MethodFreezing ratio = ratio of cooling characteristics of casting to the riser.

Th i h ld lidif l

( )( )

casting

riser

AVx

AV

=

The riser should solidify last so x > 1

According to Caine X =

Y = and a, b, c are constant.

a cY b

+−

riser

casting

VV


Table: Constants in Caine’s Method


Conventional Question IES‐2007

Calculate the size of a cylindrical riser (height and

diameter equal) necessary to feed a steel slabdiameter equal) necessary to feed a steel slab

casting of dimensions 25 x 25 x 5 cm with a side

riser, casting poured horizontally into the mould.

[Use Caine’s Method]


ChillsExternal chills are masses of high‐heat‐capacity, high‐thermal‐conductivity material that are placed in the mould (adjacent tothe casting) to accelerate the cooling of various regions.Chills can effectively promote directional solidification orincrease the effective feeding distance of a riser. They can oftenb d d h b f i i d f ibe used to reduce the number of risers required for a casting.Internal chills are pieces of metal that are placed within themould cavity to absorb heat and promote more rapidsolidification. Since some of this metal will melt during theoperation, it will absorb not only the heat‐capacity energy, butalso some heat of fusion. Since they ultimately become part ofthe final casting, internal chills must be made from the samealloy as that being cast.


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IES‐1995

Directional solidification in castings can be improved

by using

( ) Chill d h l t(a) Chills and chaplets

(b) Chills and padding

(c) Chaplets and padding

(d) Chills, chaplets and padding

[Ans. (b)]


GATE‐1998,2007

Chills are used in moulds to

(a) Achieve directional solidification

(b) Reduce the possibility of blowholes

(c) Reduce freezing time

(d) Smoothen metal flow for reducing splatter

[Ans. (a)]


IAS 1994Chills are used in casting moulds to(a) Achieve directional solidification(b) Reduce possibility of blow holes(c) Reduce the freezing time(c) Reduce the freezing time(d) Increase the smoothness of cast surface

Ans. (a)


CupolaSteel can be melted in hot blast cupola.

In hot blast cupola, the flue gases are used to preheat

the air blast to the cupola so that the temperature in p p

the furnace is considerably higher than that in a

conventional cupola.

Cupola has been the most widely used furnace for

melting cast iron.


IES‐1997Assertion (A): Steel can be melted in hot blast cupola.Reason (R): In hot blast cupola, the flue gases are used topreheat the air blast to the cupola so that the temperature inthe furnace is considerably higher than that in a

i l lconventional cupola.(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 explanation of A(c) A is true but R is false(d) A is false but R is true [Ans. (a)]


Electric Arc Furnace For heavy steel castings, the open‐hearth type of

furnaces with electric arc or oil fired would be generally

suitable in view of the large heat required for melting.

Electric arc furnaces are more suitable for ferrous

materials and are larger in capacity.


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Crucible FurnaceSmaller foundries generally prefer the crucible furnace.The crucible is generally heated by electric resistanceor gas flame.

Induction FurnaceThe 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.


LadlesTwo types of ladles used in the pouring of castings.


Casting Cleaning (fettling)Impurities in the molten metal are prevented from reaching the mould cavity by providing a (i) Strainer (ii) Button well(iii) Skim bob


GATE‐1996

Light impurities in the molten metal are preventedfrom reaching the mould cavity by providing a(a) Strainer(b) Button well(c) Skim bob(d) All of the above

Ans. (c)


Pouring timeTime taken to fill the mould with top gate

Where A = Area of mould H = Height of mouldAg = Area of Gate

Ag m

A.HtA 2gh

=

Hm = Gate height

Time taken to fill the mould with bottom gate

( )B m mg

2At h h HA 2g

= − −


GATE‐2005

A mould has a downsprue whose length is 20 cmand the cross sectional area at the base of thedownsprue is 1cm2. The downsprue feeds ah i t l l di i t th ld it fhorizontal runner leading into the mould cavity ofvolume 1000 cm3. The time required to fill themould cavity will be(a)4.05 s (b)5.05 s (c)6.05 s (d)7.25 s

Ans. (b)


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GATE‐2006In 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 gateis tA. If the same mould is filled with a bottom gate,then the time taken is tB. Ignore the time required tofill h d f i i l ff Afill the runner and frictional effects. Assumeatmospheric pressure at the top molten metal surfaces.The relation between tA and tB is(A) 2(B) 2

(C)2

(D) 2 2

B A

B A

AB

B A

t tt t

tt

t t

=

=

=

=


Expression for choke area

Where m = mass of the casting, kg

= 2mCA mmcρt 2gH

= Density of metal, kg / m3

t = pouring timec = Efficiency factor and is the function of gate

system used H = Effective head of liquid metal

= h for top gate

ρ


H=h‐ for bottom gate

=h‐ for parting line gate

mh2

2c

m

h2h

top gate parting line gate bottom gate

mh

P i li

mhCh

mh


Casting Defects The following are the major defects, which are likely to

occur in sand castings:

Gas defects

Shrinkage cavities

Molding material defects

Pouring metal defects

Mold shift.Compiled by: S K Mondal Made Easy

Gas DefectsA 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 intog yblowholes and pinhole porosity.Blowholes are spherical or elongated cavities presentin the casting on the surface or inside the casting.Pinhole porosity occurs due to the dissolution ofhydrogen gas, which gets entrapped during heating ofmolten metal.


Shrinkage CavitiesThese are caused by liquid shrinkage occurring during thesolidification of the casting.To compensate for this, proper feeding of liquid metal isrequired. For this reason risers are placed at theappropriate places in the mold.Sprues may be too thin, too long or not attached in theproper location, causing shrinkage cavities.It is recommended to use thick sprues to avoid shrinkagecavities.


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Molding Material Defects

Cuts and washes,

Scab

Metal penetration,

Fusion, and

Swell


Cut and washesThese appear as rough spots and areas of excess metal, andare caused by erosion of molding sand by the flowingmetal.This is caused by the molding sand not having enoughstrength and the molten metal flowing at high velocitystrength and the molten metal flowing at high velocity.The former can be taken care of by the proper choice ofmolding sand and the latter can be overcome by theproper design of the gating system.


ScabThis defect occurs when a portion of the face of a mouldlifts or breaks down and the recess thus made is filled bymetal.When the metal is poured into the cavity, gas may bedisengaged with such violence as to break up the sand,hi h i h h d d h l i i fill dwhich is then washed away and the resulting cavity filled

with metal.The reasons can be: ‐ too fine sand, low permeability ofsand, high moisture content of sand and uneven mouldramming.


Metal penetrationWhen molten metal enters into the gaps between sandgrains, the result is a rough casting surface.This occurs because the sand is coarse or no mold wash wasapplied on the surface of the mold. The coarser the sandgrains more the metal penetration.g p


FusionThis is caused by the fusion of the sand grains with

the molten metal, giving a brittle, glassy appearance

on the casting surface.g

The main reason for this is that the clay or the sand

particles are of lower refractoriness or that the

pouring temperature is too high.


SwellUnder the influence of metallostatic forces, the moldwall may move back causing a swell in the dimensionof the casting. A proper ramming of the mold willcorrect this defect.

InclusionsParticles of slag, refractory materials sand ordeoxidation products are trapped in the casting duringpouring solidification. The provision of choke in thegating system and the pouring basin at the top of themold can prevent this defect


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Pouring Metal DefectsThe likely defects in this category are

Mis‐runs andCold shuts

A mis‐run is caused when the metal is unable to fillthe mold cavity completely and thus leaves unfilledcavities.A cold shut is caused when two streams while meetingin the mold cavity, do not fuse together properly thusforming a discontinuity in the casting.


The mis‐run and cold shut defects are caused either bya lower fluidity of the mold or when the sectionthickness of the casting is very small. Fluidity can beimproved by changing the composition of the metaland by increasing the pouring temperature of themetalmetal.


GATE‐2004

Misrun is a casting defect which occurs due to

(a) Very high pouring temperature of the metal

(b) Insufficient fluidity of the molten metal

(c) Absorption of gases by the liquid metal

(d) Improper alignment of the mould flasks

Ans. (b)


GATE‐2009Two streams of liquid metal which are not hot

enough to fuse properly result into a casting defect

known as

(a) Cold shut

(b) Swell

(c) Sand wash

(d) Scab [Ans. (a)]Compiled by: S K Mondal Made Easy

Mold ShiftThe mold shift defect occurs when cope and drag

or molding boxes have not been properly aligned.


IES‐2001

Scab is a

(a) Sand casting defect

(b) Machining defect

(c) Welding defect

(d) Forging defect

Ans. (a)


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IAS‐2004Match List‐I (Casting Defects) with List‐II (Explanation) and select the correct answer using the codes given below the lists:List‐I List‐II(Casting Defects) (Explanation)A. Metallic projections 1. Consist of rounded or rough internal or exposed cavities

including blow holes and pin holesB. Cavities 2. Formed during melting, solidification and moulding.C. Inclusions 3. Includes single folds, laps, scars adhering sand layers and

oxide scaleD. Discontinuities 4. Include cracks, cold or hot tearing and cold shuts

5.Consist of fins, flash or massive projections and rough surfaces

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

Ans. (d)


GATE‐2003Hardness of green sand mould increases with(a) Increase in moisture content beyond 6 percent(b) Increase in permeability(c) Decrease in permeability(c) Decrease in permeability(d) Increase in both moisture content and permeability

Ans. (c)


IES‐1998Assertion (A): Stiffening members, such as webs and ribs, used on a casting should be liberally provided. Reason (R): They will provide additional strength to a cast memberto a cast member.(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)]


IES‐2005In gating system design, which one of thefollowing is the correct sequence in which chokearea, pouring time, pouring basin and sprue sizesare calculated?(a) Choke area ‐ Pouring time ‐ Pouring basin – Sprue(b) Pouring basin ‐ Sprue ‐ Choke area ‐ Pouring time(c) Choke area ‐ Sprue ‐ Pouring basin ‐ Pouring time(d) Pouring basin ‐ Pouring time ‐ Choke area ‐ Sprue


IES‐1997If the melting ratio of a cupola is 10: 1, then the coke requirement for one ton melt will be(a) 0.1 ton(b) 10 tons(b) 10 tons(c) 1 ton(d) 11 tons

Ans. (a)


IES‐2009In which one of the following furnaces most of the non‐ferrous alloys are melted?(a) Reverberatory furnace(b) Induction furnace(b) Induction furnace(c) Crucible furnace(d) Pot furnace

Ans. (d)


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IAS‐2001Which of the following pattern‐materials are used in Precision Casting?1. Plaster of Paris2. Plastics2. Plastics3. Anodized Aluminium Alloy 4. Frozen MercurySelect the correct answer using the codes given below:(a) 1 and 2 (b) 2 and 4 (c)3 and 4 (d) 1 and 3

Ans. (b)


IAS‐2004Which one of the following gating systems is bestsuited to obtain directional solidification?(a) Top grating(b) Part‐line grating(b) Part line grating(c) Bottom grating(d) Stepped grating

Ans. (d)


Cast Aluminium CodeFour digit identification systemFirst digit indicates alloy group1 – Aluminium, 99% or more2 – copper3 Silicon with copper and/or magnesium3 – Silicon, with copper and/or magnesium4 – silicon5 – magnesium6 – not used7 – zinc8 – tin9 – other elementsCompiled by: S K Mondal Made Easy

Cast Aluminium Code Contd..Second two digits identify the aluminium alloy orindicate the aluminium purity.The last digit is separating from the other three by adecimal point and indicates the product form; that is,castings or ingotscastings or ingotsA modification of the original alloy is indicated by aserial letter before the numerical designation.Alloy A514.0 indicates an aluminium alloy casting withmagnesium as the principal alloy. One modification tothe original alloy has made, as indicated by the letter A.


IES 2011In the designation of Aluminium casting A514.0indicates :(a) Aluminium purity(b) Aluminium content(c) Percentage of alloy element(d) Magnesium Content

Ans. (d)

Compiled by: S K Mondal Made Easy Compiled by: S K Mondal Made Easy

10/9/2011

1

Special CastingSpecial Casting

By S K Mondal

Shell MouldingThe sand is mixed with a thermosetting resin isallowed to come in contact with a heated metal pattern(2000C).A ki ( h ll) f b f d d l iA skin (shell) of about 3.5 mm of sand and plasticmixture 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.

A good surface finish and good size tolerance

reduce the need for machining.g

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

Shell moulding process

Molding Sand in Shell MoldingThe molding sand is a mixture of fine grained quartz sand

and powdered bakelite.

Cold coating and Hot coating methods are used forCold coating and Hot coating methods are used for

coating the sand grains with bakelite.

Cold coating: quartz sand is poured into the mixer and

then the solution of powdered bakelite in acetone and

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

soluble phenol formaldehyde resin is added. The mixer is

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

properties to the mixtures than cold method.

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2

AdvantagesDimensional accuracy.

Smoother surface finish. (Due to finer size grain used)

Very thin sections can be cast.y

Very small amount of sand is needed.

LimitationsExpensive pattern

Small size casting only.

Highly complicated shapes cannot be obtained.

More sophisticated equipment is needed for handling

the shell moldings.

ApplicationsCylinders and cylinder heads for air‐ cooled IC

engines

Automobile transmission parts.

Piston rings

IES 2010Consider the following advantages of shell mould casting:

1. Close dimensional tolerance.2. Good surface finish.3. Low cost.4. Easier.Which of these are correct?(a) 1, 2 and 3 only (b) 2, 3 and 4 only(c) 1, 2 and 4 only (d) 1, 2, 3 and 4

IES‐1996Consider the following ingredients used inmoulding:

1. Dry silica sand2.Clay2.Clay3.Phenol formaldehyde4.Sodium silicateThose used for shell mould casting include(a) 1, 2 and 4 (b) 2, 3 and 4(c) 1and 3 (d) 1, 2, 3 and 4

IES‐2005In shell moulding, how can the shell thickness be accurately maintained?

(a) By controlling the time during which the pattern is in contact with mould

(b) By controlling the time during which the pattern is heated

(c) By maintaining the temperature of the pattern in the range of 175oC – 380oC

(d) By the type of binder used

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3

IES‐2006Shell moulding can be used for:(a) Producing milling cutters(b) Making gold ornaments(c) Producing heavy and thick walled casting(c) Producing heavy and thick walled casting(d) Producing thin casting

IES 2007

Which of the following are employed in shellmoulding?1. Resin binder 2. Metal pattern 3. Heating coilsSelect the correct answer using the code givenbelow:(a) 1 and 2 only (b) 1 and 3 only(c) 2 and 3 only (d) 1, 2 and 3

IAS‐2007The mould in shell moulding process is made up

of which of the following?

(a) Gypsum + setting agents(a) Gypsum + setting agents

(b) Green sand + clay

(c) Sodium silicate + dried sand

(d) Dried silica + phenolic resin

IAS‐1999Match List I (Moulding Process) with List II (BindingAgent) and select the correct answer using the codesgiven below the lists:

List I List IIA. Green sand 1. SilicateB. Core sand 2. OrganicC. Shell moulding 3. ClayD. CO2 process 4. Plaster of Paris

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

Investment CastingInvestment casting process or lost wax processBasic steps:1. Produce expendable wax, plastic, or polystyrene patterns.2. Assemble these patterns onto a gating system3 Investing or covering the pattern assembly with refractory3. Investing or covering the pattern assembly with refractoryslurry

4.Melting the pattern assembly to remove the pattern material5. Firing the mould to remove the last traces of the patternmaterial

6.Pouring molten metal7. Knockout, cutoff and finishing.

Fig. Investment flask‐casting procedure

10/9/2011

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Ceramic Shell Investment CastingIn ceramic shell investment casting a ceramic shell is

built around a tree assembly by repeatedly dipping a

pattern into a slurry (refractory material such aspattern into a slurry (refractory material such as

zircon with binder).

After each dipping and stuccoing is completed, the

assembly is allowed to thoroughly dry before the next

coating is applied.

IES 20092 marks

AdvantagesTight dimensional tolerances

Excellent surface finish (1.2 to 3.0 μm )

Machining can be reduced or completelyg p y

eliminated

High melting point alloy can be cast, almost any

metal can be cast

Almost unlimited intricacy

Limitations

Costly patterns and moulds

Labour costs can be high

Limited size

10/9/2011

5

Applications

Aerospace and rocket components.

Vanes and blades for gas turbines.

Surgical instruments

IES 2011The proper sequence of investment casting steps is :(a) Slurry coating – pattern melt out‐Shakeout – Stuccocoating(b) Stucco coating – Slurry coating – Shakeout – Patternmelt out(c) Slurry coating – Stucco coating – Pattern melt out –Shakeout(d) Stucco coating – Shakeout – Slurry coating – Patternmelt out

GATE‐2006

An expendable pattern is used in(a) Slush casting(b) Squeeze casting(c) Centrifugal casting(d) Investment casting

IES‐1992The most preferred process for casting gas turbine blades is:(a) Die moulding(b) Shell moulding(b) Shell moulding(c) Investment moulding(d) Sand casting

JWM 2010Consider the following materials :1. Wax 2. Wood3. PlasticWhich of these materials can be used as pattern in investment casting process ?(a) 1, 2 and 3 (b) 1 and 2 only(c) 2 and 3 only (d) 1 and 3 only

IES 2010Assertion (A): These investment casting is used forprecision parts such as turbine plates, sewingmachines etc.Reason (R): The investment castings have a goodsurface finish and are exact reproductions of thesurface finish and are exact reproductions of themaster pattern.(a) Both A and R are individually true and R is thecorrect explanation of A(b) Both A and R are individually true but R is NOT thecorrect explanation of A(c) A is true but R is false(d) A is false but R is true

10/9/2011

6

IES 2007Consider the following statements in respect ofinvestment castings:1. The pattern or patterns is/are not joined to a stalk orsprue also of wax to form a tree of patterns.2.The prepared moulds are placed in an oven and heatedgently to dry off the invest and melt out the bulk of wax.3.The moulds are usually poured by placing the moulds ina vacuum chamber. Which of the statements given aboveare correct?(a) 1 and 2 only (b) 1 and 3 only(c)2 and 3 only (d) 1, 2 and 3

IES‐2006Which of the following materials are used formaking patterns in investment casting method?1. Wax 2. Rubber 3. Wood 4. PlasticSelect the correct answer using the codes given below:Select the correct answer using the codes given below:(a) Only 1 and 3 (b) Only 2 and 3(c) Only 1, 2 and 4 (d) Only 2, 3 and 4

IAS‐1996Light and intricate parts with close dimensionaltolerances of the order of ± 0.005 mm areproduced by(a) Investment castingg(b) Die casting(c) Centrifugal casting(d) Shell mould casting

Permanent Mould CastingThe process in which we use a die to make thecastings is called permanent mold casting or gravitydie casting, since the metal enters the mold undergravitygravity.Some time in die‐casting we inject the molten metalwith a high pressure. When we apply pressure ininjecting the metal it is called pressure die castingprocess.Grey cast iron is used for mould material.

AdvantagesGood surface finish and dimensional accuracyMetal mold gives rapid cooling and fine‐grainstructureMultiple‐use molds.

DisadvantagesHigh initial mold costShape, size, and complexity are limitedMold life is very limited with high‐melting‐pointmetals such an steelmetals such an steel.Low melting point metals can be cast‐ Aluminum‐ Zinc‐ Magnesium alloys‐ Brass‐ Cast iron

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Applications

Pistons/cylinders/rods

Gears

Kitchenware

Die CastingMolten metal is injected into closed metal dies under

pressures ranging from 100 to 150 MPa.

Pressure is maintained during solidificationPressure is maintained during solidification

After which the dies separate and the casting is ejected

along with its attached sprues and runners.

Cores must be simple and retractable and take the

form of moving metal segments

Video

Die casting machines can be

Hot chamber

Cold chamber

Hot chamber machines areGood for low temperature (approx. 400°C)Faster than cold chamber machinesCycle times must be short to minimize metalcontaminationMetal starts in a heated cylinderA piston forces metal into the dieThe piston retracts, and draws metal inMetal: Lead, Tin, Zinc

Hot Chamber

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Cold chamber machines

Casts high melting point metals ( > 600°C)

High pressures used

l h d blMetal is heated in a separate crucible

Metal is ladled into a cold chamber

The metal is rapidly forced into the mold before it

cools

Copper, Brass and Aluminium can cast.

AdvantagesExtremely smooth surfaces (1 µm)

Excellent dimensional accuracy

Rapid production rate

Better mechanical properties compared to sand

casting

Intricate parts possible

Minimum finishing operations

Thin sections possible

LimitationsHigh initial die cost

Limited to high‐fluidity nonferrous metals

Part size is limited

Porosity may be a problem

Some scrap in sprues, runners, and flash, but this can

be directly recycled

ApplicationsCarburettorsAutomotive partsBathroom fixturesToys

CommonmetalsAlloys of aluminum, zinc, magnesium, and leadAlso possible with alloys of copper and tin

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IES 2011Consider the following advantages of die casting oversand casting :1. Rapidity of the process2. Smooth surface3 Strong dense metal structure3. Strong dense metal structureWhich of these advantages are correct ?(a) 1, 2 and 3(b) 1 and 2 only(c) 2 and 3 only(d) 1 and 3 only

IES‐2009Which of the following are the most suitablematerials for die casting?(a) Zinc and its alloys(b) Copper and its alloys(b) Copper and its alloys(c) Aluminium and its alloys(d) Lead and its alloys

JWM 2010Assertion (A) : In die casting method, smallthickness can be filled with liquid metal.Reason (R) : The air in die cavity trapped inside thecasting causes problems.(a) Both A and R are individually true and R is the (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

IES‐2005Which one of the following processes produces acasting when pressure forces the molten metalinto themould cavity?(a) Shell moulding (b) Investment castingg g(c) Die casting (d) Continuous casting

IES‐2006In which of the following aremetal moulds used?(a) Greensand mould(b) Dry sand mould(c) Die casting process(c) Die casting process(d) Loammoulding

IES‐1995Assertion (A): An aluminium alloy with 11 % silicon isused for making engine pistons by die castingtechnique.Reason (R): Aluminium has low density and additionof silicon improves its fluidity and therefore itsp ycastability.(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 explanation of A(c) A is true but R is false(d) A is false but R is true

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IES‐1995Match List I with List II and select the correct answer taking the help of codes given below the lists:List I List II (Products) (Process of manufacture)A. Automobile piston in aluminium alloy 1. Pressure die‐castingB. Engine crankshaft in spheroidal

hi i G i di igraphite iron 2. Gravity die‐castingC. Carburettor housing in aluminium alloy 3. Sand castingD. Cast titanium blades 4. Precision investment

casting5. Shell moulding

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

IAS‐2007Consider the following statements:1. Zinc die castings have low strength.2. In the die casting process, very thin sections or complex shapes can be obtained easily.complex shapes can be obtained easily.Which of the statements given above is/are correct?(a) 1 only(b) 2 only(c) Both 1 and 2(d) Neither 1 nor 2

IAS‐1996Assertion (A): Die casting yields a product of goodaccuracy and finish.Reason (R): Low melting alloys used in diecasting.( ) B h A d R i di id ll d R i h(a) Both A and R are individually true and R is thecorrect explanation of A(b) Both A and R are individually true but R is not thecorrect explanation of A(c) A is true but R is false(d) A is false but R is true

IES 2011Consider the following statements :1. Hot chamber machine is used for casting zinc, tin andother low melting alloys.2. Cold chamber machine is used for die casting offerrous alloys3. Rapid cooling rate in die casting produces highstrength and quality in many alloys.Which of these statements are correct?(a) 1, 2 and 3 (b) 1 and 2 only(c) 2 and 3 only (d) 1 and 3 only

GATE‐2007Which of the following engineering materials isthe most suitable candidate for hot chamber diecasting?

( ) b l(a) Low carbon steel(b) Titanium(c) Copper(d) Tin

IES‐1995Assertion (A): Aluminium alloys are cast in hotchamberdie casting machine.Reason (R): Aluminium alloys require high meltingwhen compared to zinc alloys.(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 correctexplanation of A(b) Both A and R are individually true but R is not thecorrect explanation of A(c) A is true but R is false

(d) A is false but R is true

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Centrifugal CastingProcess: Molten metal is introduced into a rotating sand,

metal, or graphite mould, and held against the mould

wall by centrifugal force until it is solidified

A mold is set up and rotated along a vertical (rpm isA mold is set up and rotated along a vertical (rpm is

reasonable), or horizontal (200‐1000 rpm is reasonable)

axis.

The mold is coated with a refractory coating.

During cooling lower density impurities will tend to rise

towards the center of rotation.Fig. True centrifugal casting

PropertiesThe mechanical properties of centrifugally cast jobs arebetter compared to other processes, because the inclusionssuch as slag and oxides get segregated towards the centreand can be easily removed by machining. Also, thepressure acting on the metal throughout the solidificationp g gcauses the porosity to be eliminated giving rise to densemetal.No cores are required for making concentric holes in thecase of true centrifugal casting.

AdvantagesFine grained structure at the outer surface of thecasting free of gas and shrinkage cavities andporosityFormation of hollow interiors in cylinders withoutcoresCan produce a wide range of cylindrical parts,including ones of large size.Good dimensional accuracy, soundness, andcleanlinessThere is no need for gates and runners, whichincreases the casting yield, reaching almost 100 %.

LimitationsMore segregation of alloy component during pouring under

the forces of rotation

Contamination of internal surface of castings with non‐

lli i l imetallic inclusions

Inaccurate internal diameter

Shape is limited.

Spinning equipment can be expensive

Poor machinability

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Common metalsIronsteelstainless steelalloys of aluminium, copper, and nickel

GATE‐2002In centrifugal casting, the impurities are

(a) Uniformly distributed(b) Forced towards the outer surface(c) Trapped near the mean radius of the casting(d) Collected at the centre of the casting

GATE‐1993Centrifugally cast products have(a) Large grain structure with high porosity(b) Fine grain structure with high density(c) Fine grain structure with low density(c) Fine grain structure with low density(d) Segregation of slug towards the outer skin of thecasting

IES‐2008Which of the following casting processes does not/do not require central core for producing pipe?1. Sand casting process2. Die casting process3 Centrifugal casting process3. Centrifugal casting processSelect the correct answer using the code given below:(a) 1 and 2(b) 2 only(c) 2 and 3(d) 3 only

IES‐2009Which one of the following casting processes is

best suited to make bigger size hollow

symmetrical pipes?y p p

(a) Die casting

(b) Investment casting

(c) Shell moulding

(d) Centrifugal casting

IES 2007Which one of the following is the correctstatement?In a centrifugal casting method(a) No core is used(a) No core is used(b) Core may be made of any metal(c) Core is made of sand(d) Core is made of ferrous metal

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IES‐1998Poor machinability of centrifugally cast iron pipe is due to(a) Chilling(b) Segregation(b) Segregation(c) Dense structure(d) High mould rotation speed

IES‐2009Which of the following are the most likelycharacteristics in centrifugal casting?(a) Fine grain size and high porosity(b) Coarse grain size and high porosity(b) Coarse grain size and high porosity(c) Fine grain size and high density(d) Coarse grain size and high density

IES 2007Match List I with List II and select the correct answer using the code given below the Lists:List I List II(Casting Process) (Principle)A. Die casting 1.The metal solidifies in a rotating mouldB. Investment casting 2.The pattern cluster is repeatedly dipped

into a ceramic slurry and dusted with frefractory

C. Shell moulding 3. Molten metal is forced by pressure into a metallic mould

D. Centrifugal casting 4. After cooling, the invest is removed from the Casting by pressure jetting or vibratory cleaning

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

IES‐2000Match List I (Process) with List II (Products/materials) and select the correct answer using the codes given below the Lists:List I List IIA. Die casting 1. Phenol formaldehydeB. Shell molding 2. C.I. pipesC. CO2 molding 3. Non‐ferrous alloysD. Centrifugal casting 4. Sodium silicate


IAS‐2004Match List‐I (Name of the Process) with List‐II (Advantage) and select the correct answer using the codes given below the lists:List‐I List‐II(Name of the Process) (Advantage)A. Sand Casting 1. Large cylindrical parts with good qualityB C i ld i E ll di i l d fB. Ceramic mold casting 2.Excellent dimensional accuracy and surface

finishC. Die casting 3. Intricate shapes and close tolerance partsD. Centrifugal casting 4. Almost any metal is cast and there if no limit to

size, shape and weight5. Good dimensional accuracy, finish and lowporosity

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

(c) 2 1 5 3 (d) 4 3 2 1

Semi‐centrifugal CastingCentrifugal force assists the flow of metal from a

central reservoir to the extremities of a rotating

symmetrical mold, which may be either expendable ory , y p

multiple‐use

Rotational speeds are lower than for true centrifugal

casting

Cores can be used to increase the complexity of the

product.

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Fig. Semi‐centrifugal casting

IAS‐2003Assertion (A): Semi‐centrifugal casting process issimilar to true centrifugal casting except that thecentral core is used in it to form inner surface.Reason (R): In semi‐centrifugal casting process theaxis of spin is always verticalp y(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 explanation of A(c) A is true but R is false(d) A is false but R is true

CentrifugingUses centrifuging action to force the metal from a central

pouring reservoir into separate mold cavities that are

offset from the axis of rotation.

Low speed

May used to assist in the pouring of investment casting

trees.

Fig. Method of casting by the centrifuging process

IES‐2000Match List I (Type of casting) with List II (Working principles) and select the correct answer using the codes given below the Lists:List I List IIA. Die casting 1. Molten metal is forced into the die

under pressureB. Centrifugal casting 2. Axis of rotation does not coincide with

axis of mouldC. Centrifuging 3. Metal solidifies when mould is rotatingD. Continuous casting 4. Continuously pouring molten metal

into mouldCodes:A B C D A B C D

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

Dry Sand MoldingTo reduce gas forming materials air dried mould used.

Types:

1 Skin drying and1.Skin drying and

2.Complete mold drying

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Slush CastingSlush casting is a variation of the permanent mold processin which the metal is permitted to remain in the mold onlyuntil a shell of the desired thickness has formed.The mold is then inverted and the remaining liquid ispoured out.When the mold halves are separated, the resulting castingis a hollow shape with good surface detail but variable wallthickness.Frequently used to cast low‐melting‐temperature metalsinto ornamental objects such as candlesticks, lamp bases,and statuary.

IAS‐2004Which of the following are produced by slushcasting?(a) Hollow castings with thick walls(b) Hollow castings with thin walls(b) Hollow castings with thin walls(c) Thin castings(d) Thick castings

IES 2011The method of casting for producing ornamental piecesare:(a) Slush and gravity casting(b) Pressed and slush casting(c) Gravity and semi permanent mould casting(d) Semi permanent mould and pressed casting

Squeeze CastingProcess:1. Molten metal is poured into an open face die.2. A punch is advanced into the die, and to the metal.3 Pressure (less than forging) is applied to the punch3.Pressure (less than forging) is applied to the punchand die while the part solidifies.

4.The punch is retracted, and the part is knocked outwith an ejector pin.Overcomes problems with feeding the die, andproduces near net, highly detailed parts.

IAS‐2002Match List I (Casting Process) with List II (Applications) and select the correct answer using the codes given below the Lists:List I List II(Casting Process) (Applications)A. Centrifugal casting 1. CarburetorB. Squeeze casting 2. PipesC. Die Casting 3. Wheels for

automobiles4. Gear housings

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

Single Crystal CastingThe process is effectively:1. Prepare a mold so that one end is a heated oven, and

the other end chilled. The part should be oriented so that the cooling happens over the longest distance.C t t l i t th ld2. Cast metal into the mold

3. Solidification will begin at the chill plate. These dendrites will grow towards the heated end of the part as long dendritic crystals. The part is slowly pulled out of the oven, past the chill plate.

4. Remove the solidified part.

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Creep and thermal shock resistance properties.

IES 2009

2 marks

Plaster CastingProcess: A slurry of plaster, water, and various additives isadditives is pouted over a pattern and allowed to set. Thepattern is removed and the mould is baked to removeexcess water. After pouring and solidification, the mould isbroken and the casting is removed.gAdvantage: High dimensional accuracy and smoothsurface finish, thin sections and intricate detail canproduce.Limitations: Lower‐temperature nonferrous metals only:Commonmetals: Primarily aluminium and copper

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

IES‐1996Which of the following pairs are correctly matched?1. Pit moulding ..................For large jobs.2. Investment moulding ... Lost wax process.3 Plaster moulding Mould prepared in 3. Plaster moulding ……… Mould prepared in gypsum.(a) 1, 2 and 3 (b) 1 and 2(c) 1 and 3 (d) 2 and 3

Loam Moulding

Moulding loam is generally artificially composed of

common brick‐clay, and sharp sand.

Loammeans mud.

LoamMoulding is restricted to forms which cannot be

cast conveniently in any other process.

It is costly.

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IES‐1997Which one of the following pairs is not correctlymatched?(a) Aluminium alloy piston …………Pressure die casting(b) Jewellery……………………….. Lost wax process(b) Jewellery……………………….. Lost wax process(c) Large pipes ……………………..Centrifugal casting(d) Large bells ………………………Loam moulding

GATE‐1998List I List II (A) Sand casting (1) Symmetrical and circular shapes only(B) Plaster mould casting (2) Parts have hardened skins and soft interior(C) Shell mould casting (3) Minimum post‐casting processing(D) Investment casting (4) Parts have a tendency

to warp(5) Parts have soft skin

and hard interior(6) Suitable only for non‐

ferrous metals

GATE‐1992Match the following moulding/casting processes with the product:Moulding/Casting processes Product(A) Slush casting (P) Turbine blade(B) Shell moulding (Q) Machine tool bed(B) Shell moulding (Q) Machine tool bed(C) Dry sand moulding (R) Cylinder block(D) Centrifugal casting (S) Hollow castings

like lamp shades(T) Rain water pipe(U) Cast iron shoe brake

GATE‐1996List I List II(A) Rivets for aircraft body 1. Forging(B) Carburettor body 2. Cold heading(C) Crankshafts 3 Aluminium‐based (C) Crankshafts 3. Aluminium‐based

alloy(D) Nails 4. Pressure die casting

5. Investment casting

IES‐2003Match List I (Products) with List II (Casting Process) and select the correct answer using the codes given below the Lists:List I List II(Products) (Casting Process)A. Hollow statues 1. Centrifugal CastingB Dentures 2 Investment CastingB. Dentures 2. Investment CastingC. Aluminium alloy pistons 3. Slush CastingD. Rocker arms 4. Shell Moulding

5. Gravity Die CastingCodes:A B C D A B C D

(a) 3 2 4 5 (b) 1 3 4 5(c) 1 2 3 4 (d) 3 2 5 4

IES‐1993Match the items of List I (Equipment) with the items of List II (Process) and select the correct answer using the given codes.List I (Equipment) List II (Process)P ‐ Hot Chamber Machine 1 CleaningP ‐ Hot Chamber Machine 1. CleaningQ ‐Muller 2. Core makingR ‐ Dielectric Baker 3. Die castingS ‐ Sand Blaster 4. Annealing

5. Sand mixing(a) P‐2, Q‐1, R‐4, S‐5 (b) P‐4, Q‐2, R‐3, S‐5(c) P‐4, Q‐5, R‐1, S‐2 (d) P‐3, Q‐5, R‐2, S‐1

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IAS‐2004Match List‐I (Name of the Casting Process) with List‐II (Process Definition) and select the correct answer using the codes given below the lists:List‐I List‐II (Name of the Casting Process) (Process Definition)A. Die casting 1.This process involves use of a mould made of

Dried silica sand and phenolic resin mixtureB El l i I hi l l i f d bB. Electroslag casting 2. In this process, molten metal is forced by

Pressure into a metal mouldC. Centrifugal casting 3. This process employs a consumable electrodeD. Precision casting 4. This process involves rotating a mould while the

metal solidifies5. This process produces very smooth, highlyAccurate castings from both ferrous and nonferrous alloys


Q. No Option

1 A2 A3 C4 A5 D

Q. No Option

13 C14 D15 D16 B17 B

Conventional Casting Process Ch‐21

6 A7 D8 C9 B10 D11 A12 B

18 B19 D20 A21 A

Q. No Option

1 D2 C3 C4 B

Q. No Option

11 A12 A13 D14 A

Special Casting Process Ch‐22

5 C6 A7 D8 C9 B10 D

14 A15 A16 B17 A

Documents

Metal Casting Complete PPT With Question Ans 2