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Sand casting
y Sand casting uses ordinary sand as the primary
mould material.
Metal Casting y The sand grains are mixed with small amounts of
other materials, such as clay and water, to improve
By S K Mondal
mouldability and cohesive strength, and are then
Compiled by: S K Mondal Made Easy packed around a pattern that has the shape of the
desired casting.
y The pattern must be removed before pouring, the
mold is usually made in two or more pieces.
y An opening called a sprue hole is cut from the top of
the mold through the sand and connected to a
system of channels called runners.Compiled by: S K Mondal Made Easy Contd….
y The molten metal is poured into the sprue hole, flows
through the runners, and enters the mold cavity
through an opening called a gate.
y Gravity flow is the most common means of
introducing the metal into the mold.
y After solidification, the mold is broken and the
finished casting is removed.
y The casting is then “fettled” by cutting off the ingate
and the feeder head.
y Because the mold is destroyed, a new mold must be
made for each casting.
Compiled by: S K Mondal Made Easy Contd… Compiled by: S K Mondal Made Easy
Sequential steps in making a sand casting y The mold is opened, the pattern board is drawn
(removed), and the runner and gate are cut into the
y A pattern board is placed between the bottom (drag) surface of the sand.
and top (cope) halves of a f lask, with the bottom side up.
y The mold is reassembled with the pattern board
y Sand is then packed into the drag half of the mold. removed, and molten metal is poured through the
sprue.
y A bottom board is positioned on top of the packed sand,
and the mold is turned over, showing the top (cope) half y The contents are shaken from the flask and the metal
of pattern with sprue and riser pins in place. segment is separated from the sand, ready for further
processing.
y The cope half of the mold is then packed with sand.
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Compiled by: S K Mondal Made Easy Compiled by: S K Mondal Made Easy
Casting Terms y Pattern: Pattern is a replica of the final object to be
made with some modifications.
y Flask: A moulding flask is one which holds the sand
mould intact. It is made up of wood for temporary y Parting line: This is the dividing line between the two
applications or metal for long‐term use. moulding flasks that makes up the sand mould.
y Drag: Lower moulding flask. y Bottom board: This is a board normally made of wood,
which is used at the start of the mould making.
y Cope: Upper moulding flask.
y Cheek: Intermediate moulding flask used in three‐
piece moulding.
Compiled by: S K Mondal Made Easy Contd… Compiled by: S K Mondal Made Easy Contd…
y Moulding sand: The freshly prepared refractory y Pouring basin: A small funnel‐shaped cavity at the top
material used for making the mould cavity. It is a of the mould into which the molten metal is poured.
mixture of silica, clay and moisture in appropriate
proportions. y Sprue: The passage through which the molten metal
from the pouring basin reaches the mould cavity.
y Backing sand: This is made up of used and burnt
sand. y Runner: The passage ways in the parting plane through
which molten metal flow is regulated before they reach
y Core: Used for making hollow cavities in castings. the mould cavity.
Compiled by: S K Mondal Made Easy y Gate: The actual entry point through which molten
metal enters the mould cavity in a controlledCompiled by: S K Mondal Made Easy rate. Contd…
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y Chaplet: Chaplets are used to support cores inside the Padding
mould cavity. y Tapering of thinner section towards thicker section
is known as 'padding'.
y Chill: Chills are metallic objects, which are placed in
y This will require extra material.
the mould to increase the cooling rate of castings. y If padding is not provided, centre line shrinkage or
y Riser: It is a reservoir of molten metal provided in the porosity will result in the thinner section.
casting so that hot metal can flow back into the mould Compiled by: S K Mondal Made Easy
cavity when there is a reduction in volume of metal due
to solidification
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IES‐2001 IES‐1996
The main purpose of chaplets is Which of the following methods are used for
(a) To ensure directional solidification obtaining directional solidification for riser design
(b) To provide efficient venting 1. Suitable placement of chills
(c) For aligning the mold boxes 2. Suitable placement of chaplets
(d) To support the cores 3. Employing padding
Ans. (d) Select the correct answer.
(a) 1 and 2 (b) 1 and 3 (c) 2 and 3 (d) 1, 2 and 3
Compiled by: S K Mondal Made Easy Ans. (b)
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IES 2007 GATE‐2009
Which one of the following is the correct Match the items in Column I and Column II.
statement?
Gate is provided in moulds to Column I Column II
(a) Feed the casting at a constant rate
(b) Give passage to gases P. Metallic Chills 1. Support for the core
(c) Compensate for shrinkage
(d) Avoid cavities Q. Metallic Chaplets 2. Reservoir of the molten metal
Ans. (a)
R. Riser 3. Control cooling of critical
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S. 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‐1992 GATE 2011
In a green‐sand moulding process, uniform Green sand mould indicates that
ramming leads to (a) polymeric mould has been cured
(b) mould has been totally dried
(a) Less chance of gas porosity (c) mould is green in colour
(d) mould contains moisture
(b) Uniform flow of molten metal into the mould
cavity Ans. (d)
(c) Greater dimensional stability of the casting Compiled by: S K Mondal Made Easy
(d) Less sand expansion type of casting defect
Ans. (c)
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Pattern Pattern Allowances
A pattern is a replica of the object to be made by the 1. Shrinkage or contraction allowance
casting process, with some modifications. 2. Draft or taper allowance
The main modifications are 3. Machining or finish allowance
y The addition of pattern allowances, 4. Distortion or camber allowance
y The provision of core prints, and 5. Rapping allowance
y Elimination of fine details, which cannot be obtained
by casting and hence are to be obtained by further Compiled by: S K Mondal Made Easy
processing
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Shrinkage allowance Liquid shrinkage and solid shrinkage
y All metals shrink when cooling except perhaps y Liquid shrinkage refers to the reduction in
bismuth. volume when the metal changes from liquid to
solid state at the solidus temperature. To account
y This is because of the inter‐atomic vibrations which for this, risers are provided in the moulds.
are amplified by an increase in temperature.
y Solid shrinkage is the reduction in volume
y The shrinkage allowance is always to be added to the caused, when a metal loses temperature in the
linear dimensions. Even in case of internal dimensions. solid state. The shrinkage allowance is provided to
take care of this reduction.
Compiled by: S K Mondal Made Easy Contd…
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y Pattern Allowances IES‐1995
Cast Iron 10 mm/m Which one of the following materials will require
the largest size of riser for the same size of casting?
Brass, Copper, Aluminium 15 mm/m
Steel 20 mm/m
Zinc, Lead 25 mm/m (a) Aluminium
y In grey cast iron and spheroidal graphite iron, the (b) Cast iron
amount of graphitization controls the actual
shrinkage. When graphitization is more, the (c) Steel
shrinkage would be less and vice versa.
(d) Copper
Ans. (c)
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GATE‐1999 IES‐1999
Which of the following materials requires the In solidification of metal during casting,
largest shrinkage allowance, while making a
pattern for casting? compensation for solid contraction is
(a) Aluminium
(b) Brass (a) Provided by the oversize pattern
(c) Cast Iron
(d) Plain Carbon Steel (b) Achieved by properly placed risers
Ans. (d)
(c) Obtained by promoting directional
Compiled by: S K Mondal Made Easy solidification
(d) Made by providing chills
Ans. (a) Compiled by: S K Mondal Made Easy
GATE‐2001 GATE‐2004
Shrinkage allowance on pattern is provided to Gray cast iron blocks 200 x 100 x 10 mm are to be
compensate for shrinkage when cast in sand moulds. Shrinkage allowance for
pattern making is 1%. The ratio of the volume of
(a) The temperature of liquid metal drops from pattern to that of the casting will be
pouring to freezing temperature (a) 0.97 (b) 0.99 (c) 1.01 (d) 1.03
Ans. (d)
(b) The metal changes from liquid to solid state at
freezing temperature Compiled by: S K Mondal Made Easy
(c) The temperature of solid phase drops from 5
freezing to room temperature
(d) The temperature of metal drops from pouring
to room temperature
Ans. (c) Compiled by: S K Mondal Made Easy
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GATE‐2008 GATE 2011
While cooling, a cubical casting of side 40 mm A cubic casting of 50 mm side undergoes volumetric
undergoes 3%, 4% and 5% volume shrinkage solidification shrinkage and volumetric solid
during the liquid state, phase transition and solid contraction of 4% and 6% respectively. No riser is
state, respectively. The volume of metal used. Assume uniform cooling in all directions. The
compensated from the riser is side of the cube after solidification and contraction is
(a) 2% (b) 7% (c) 8% (d) 9% (a) 48.32 mm
Ans. (b) (b) 49.90 mm
(c) 49.94 mm
Compiled by: S K Mondal Made Easy (d) 49.96 mm
Ans. (a)
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IAS‐1995 IAS‐2003
Assertion (A): A pattern is made exactly similar to the Match List I (Material to be cast) with List II
part to be cast. (Shrinkage Allowance in mm/m) and select the
Reason (R): Pattern is used to make the mould cavity correct answer using the codes given below the lists:
for pouring in molten for casting.
(a) Both A and R are individually true and R is the correct List‐I List‐II
explanation of A
(b) Both A and R are individually true but R is not the (Material to Cast) (Shrinkage Allowance in mm/m)
correct explanation of A
(c) A is true but R is false (A) Grey cast iron 1. 7 ‐ 10
(d) A is false but R is true
Ans. (d) (B) Brass 2. 15
Compiled by: S K Mondal Made Easy (C) Steel 3. 20
(D) Zinc 4. 24 [Ans. (c)]
Codes:A B C D ABCD
(a) 1 2 3 4 (b) 3 4 1 2
(c) 1 4 3 2 (d) 3 2 1 4
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Draft Compiled by: S DK MRoAndFalT A L L O MWadAe ENasCy E
y To 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.
y Inner surfaces of the pattern require higher draft than
outer surfaces.
y Draft is always provided as an extra metal.
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Shake Allowance Distortion Allowance
y At the time of pattern removal, the pattern is rapped y A metal when it has just solidified is very weak and
all around the vertical faces to enlarge the mould therefore is likely to be distortion prone.
cavity slightly to facilitates its removal.
y This is particularly so for weaker sections such as long
y It is a negative allowance and is to be applied only to flat portions, V, U sections or in a complicated casting
those dimensions, which are parallel to the parting which may have thin and long sections which are
plane. connected to thick sections.
Compiled by: S K Mondal Made Easy y The foundry practice should be to make extra
material provision for reducing the distortion.
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Pattern Materials The pattern material should be
y Wood patterns are relatively easy to make. Wood is not y Easily worked, shaped and joined
very dimensionally stable. Commonly used teak, white y Light in weight
pine and mahogany wood. y Strong, hard and durable
y Resistant to wear and abrasion
y Metal patterns are more expensive but are more y Resistant to corrosion, and to chemical reactions
dimensionally stable and more durable. Commonly used y Dimensionally stable and unaffected by variations in
CI, Brass, aluminium and white metal.
temperature and humidity.
y Hard plastics, such as urethanes, and are often preferred y Available at low cost.
with processes that use strong, organically bonded sands
that tend to stick to other pattern materials. Compiled by: S K Mondal Made Easy
y In the full‐mold process, expanded polystyrene (EPS) is
used.
y Investment casting uses wax patterns.
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IES‐1994 GATE‐2000
Which of the following materials can be used for Disposable patterns are made of
making patterns? (a) Wood
(b) Rubber
1. Aluminium 2. Wax 3. Mercury 4. Lead (c) Metal
(d) Polystyrene
Select the correct answer using the codes given below: Ans. (d)
Codes: Compiled by: S K Mondal Made Easy
(a) 1,3 and 4 (b) 2,3 and 4 (c) 1, 2 and 4 (d) 1, 2 and 3
Ans. (d)
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Types of Pattern Types of Pattern
Single Piece Pattern Split Pattern or Two Piece Pattern
These are inexpensive and the simplest type of This is the most widely used type of pattern for intricate
patterns. As the name indicates, they are made of a castings. When the contour of the casting makes its
single piece. withdrawal from the mould difficult, or when the depth
of the casting is too high, then the pattern is split into two
Gated Pattern parts so that one part is in the drag and the other in the
Gating and runner system are integral with the cope.
pattern. This would eliminate the hand cutting of
the runners and gates and help in improving the Compiled by: S K Mondal Made Easy
productivity of a moulding.
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Types of Pattern Types of Pattern
y Cope and Drag Pattern y Match Plate Pattern
These are similar to split patterns. In addition to The cope and drag patterns along with the
splitting the pattern, the cope and drag halves of gating and the risering are mounted on a single
the pattern along with the gating and riser systems
are attached separately to the metal or wooden matching metal or wooden plate on either side.
plates along with the alignment pins. They are
called the cope and drag patterns. Compiled by: S K Mondal Made Easy
Compiled by: S K Mondal Made Easy
Types of Pattern Types of Pattern
y Loose Piece Pattern y Follow Board Pattern
This type of pattern is also used when the
contour of the part is such that withdrawing the This type of pattern is adopted for those
pattern from the mould is not possible. castings where there are some portions, which
are structurally weak and if not supported
properly are likely to break under the force of
ramming.
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IES‐2008 Types of Pattern
The pattern adopted for those castings where there y Sweep Pattern
are some portions which are structurally weak and It is used to sweep the complete casting by means
are likely to break by the force of ramming are of a plane sweep. These are used for generating
called: large shapes, which are axi‐symmetrical or
(a) Loose piece pattern prismatic in nature such as bell‐shaped or
(b) Follow board pattern cylindrical.
(c) Skelton pattern
(d) Single piece pattern Compiled by: S K Mondal Made Easy
Ans. (b)
Compiled by: S K Mondal Made Easy
Types of Pattern Cooling Curve
y Skeleton Pattern Compiled by: S K Mondal Made Easy
A skeleton of the pattern made of strips of wood
is used for building the final pattern by packing
sand around the skeleton. After packing the
sand, the desired form is obtained with the help
of a strickle. This type of pattern is useful
generally for very large castings, required in
small quantities where large expense on
complete wooden pattern is not justified.
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Fluidity Core
The ability of a metal to flow and fill a mold is known y Used for making cavities and hollow projections.
as fluidity.
y All sides of core are surrounded by the molten metal
Pouring Temperature and are therefore subjected to much more severe
thermal and mechanical conditions and as a result the
y The most important controlling factor of fluidity is the core sand should be of higher strength than the
pouring temperature or the amount of superheat. moulding sand.
y Higher the pouring temperature, the higher the fluidity. Compiled by: S K Mondal Made Easy
y Excessive temperatures should be avoided, however. At
high pouring temperatures, metal‐mold reactions are
accelerated and the fluidity may be so great as to permit
penetration.
y Penetration is a defect where the metal not only fills the
mold cavity but also fills the small voids between the sand
particles in a sand mold.
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Desired characteristics of a core y Permeability: Gases evolving from the molten metal
and generated from the mould may have to go
y Green Strength: A core made of green sand should through the core to escape out of the mould. Hence
be strong enough to retain the shape till it goes for
baking. cores are required to have higher permeability.
y Dry Strength: It should have adequate dry strength y Permeability Number: The rate of flow of air passing
so that when the core is placed in the mould, it through a standard specimen under a standard pressure is
should be able to resist the metal pressure acting on termed as permeability number.
it.
y The standard permeability test is to measure time
y Refractoriness: Since in most cases, the core is taken by a 2000 cu cm of air at a pressure typically of
surrounded all around it is desirable that the core 980 Pa (10 g/cm2), to pass through a standard sand
material should have higher refractoriness.
specimen confined in a specimen tube. The standard
specimen size is 50.8 mm in diameter and a length of
Compiled by: S K Mondal Made Easy Contd… 50.8 mm. Compiled by: S K Mondal Made Easy
y Then, the permeability number, R is obtained by y Calculate the permeability number of sand if it takes 1 min
R = VH 25 s to pass 2000 cm3 of air at a pressure of5 g/cm2 through
pAT the standard sample.
p = 5.0 g / cm2
Where V= volume of air = 2000 cm3 T = 1min 25 s = 1.417 min
H = height of the sand specimen = 5.08 cm R = 501.28 = 70.75
p = air pressure, g/cm2 5 ×1.417
A = cross sectional area of sand specimen = 20.268 cm2
T = time in minutes for the complete air to pass through Compiled by: S K Mondal Made Easy
Inserting the above standard values into the
expression, we get
R = 501.28
p.T
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y Collapsibility: At the time of cooling, casting shrinks, Core Sands
and unless the core has good collapsibility (ability to
decrease in size) it is likely to provide resistance against y Used clay free silica sand.
shrinkage and thus can cause hot tears. y Binders used are linseed oil, core oil, resins, dextrin,
y Friability: The ability to crumble should be a very molasses, etc.
important consideration at the time of removal. y Core oils are mixtures of linseed, soy, fish and
y Smoothness: Surface of the core should be smooth for petroleum oils and coal tar.
good finish to the casting. y The general composition of a core sand mixture could
y Low Gas Emission be core oil (1%) and water (2.5 to 6%).
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Carbon Dioxide Moulding y The compressive strength of the bond increases with
standing time due to dehydration.
y Sodium silicate (water glass, SiO2:Na2O) is used as a binder.
This is essentially a quick process of core or mould y Because of the high strength of the bond, the core need not
be provided with any other reinforcements.
preparation.
y It does not involve any distortions due to baking and also
y The mould is prepared with a mixture of sodium silicate and better dimensional accuracies are achieved.
sand and then treated with carbon dioxide for two to three
minutes such that a dry compressive strength of over 1.4 y The sand mixture does not have good shelf life and
MPa is arrived. therefore should be used immediately after preparation.
y The carbon dioxide is expected to form a weak acid, which Compiled by: S K Mondal Made Easy
hydrolyses the sodium silicate resulting in amorphous silica,
which forms the bond.
y The introduction of CO2 gas starts the reaction by forming
hydrated sodium carbonate (Na2CO3 + H2O).
Compiled by: S K Mondal Made Easy Contd…
IES‐2002 Moulding Sand Composition
Assertion (A): In CO2 casting process, the mould or y Sand: Ordinary silica Sand (SiO2), zircon, or olivine
core attains maximum strength. sands.
Reason (R): The optimum gassing time of CO2 y Clay: Acts ss binding agents mixed to the moulding
through the mould or core forms Silica Gel which sands
Kaolinite or fire clay (Al2O3 2SiO2 2H2O), and
imparts sufficient strength to the mould or core. Bentonite (Al2O3 4SiO2 H2O nH2O).
(a) Both A and R are individually true and R is the y Water: Clay is activated by water.
correct explanation of A
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(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) Compiled by: S K Mondal Made Easy
Other Additives Moulding Sand Properties
y Cereal binder up to 2% increases the strength. y Porosity or Permeability: Permeability or porosity of
y Pitch if used up to 3% would improve the hot the moulding sand is the measure of its ability to
permit air to flow through it.
strength.
y Saw dust up to 2% may improve the collapsibility by y Strength: It is defined as the property of holding
together of sand grains. A moulding sand should have
slowly burning, and increase the permeability. ample strength so that the mould does not collapse or
y Other materials: sea coal, asphalt, fuel oil, graphite, get partially destroyed during conveying, turning over
or closing.
molasses, iron oxide, etc.
y Refractoriness: It is the ability of the moulding sand
Compiled by: S K Mondal Made Easy mixture to withstand the heat of melt without showing
any signs of softening or fusion.
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y Plasticity: It is the measure of the moulding sand to flow Other Sands
around and over a pattern during ramming and to uniformly
fill the f lask. y Facing sand: The small amount of carbonaceous
material sprinkled on the inner surface of the mold
y Collapsibility: This is the ability of the moulding sand to cavity to give a better surface finish to the castings.
decrease in volume to some extent under the compressive
forces developed by the shrinkage of metal during freezing y Backing sand: It is what constitutes most of the
and subsequent cooling. refractory material found in the mould. This is made
up of used and burnt sand.
y Adhesiveness: This is the property of sand mixture to
adhere to another body (here, the moulding f lasks). The y Green Sand: The molding sand that contains
moulding sand should cling to the sides of the moulding moisture is termed as green sand. The green sand
boxes so that it does not fall out when the f lasks are lifted should have enough strength so that the constructed
and turned over. This property depends on the type and mould retains its shape.
amount of binder used in the sand mix.
y Dry sand: When the moisture in the moulding sand is
Compiled by: S K Mondal Made Easy completely expelled, it is called dryCompiled by: S K Mondal Made Easy sand.
IES‐2008 Grain size number
Small amount of carbonaceous material sprinkled y ASTM (American Society for Testing and Materials)
on the inner surface of mould cavity is called grain size number, defined as
(a) Backing sand N 2n-1
(b) Facing sand
(c) Green sand y Where N is the number of grains per square inch
(d) Dry sand visible in a prepared specimen at 100X and n is the
Ans. (b) ASTM grain‐size number. Low ASTM numbers mean a
few massive grains; high numbers refer to many small
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IES‐2002 Casting Yield
In the grain ‐size determination using standard The casting yield is the proportion of the actual
charts, the relation between the given size casting mass, w, to the mass of metal poured into the
number n and the average number of grains 'N' mould, W, expressed as a percentage.
per square inch at a magnification of 100 X is
(a) N = 2n Casting yield = w ×100
(b) N = 2n‐l W
(c) N = 2n + 1
(d) N = 2n + 1 Compiled by: S K Mondal Made Easy
Ans. (b)
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Gating System Gating System
y Pouring basin: A small funnel shaped cavity at the
top of the mould into which the molten metal is
poured.
y Sprue: The passage through which the molten metal,
from the pouring basin, reaches the mould cavity. In
many cases it controls the flow of metal into the
mould.
y Runner: The channel through which the molten
metal is carried from the sprue to the gate.
Compiled by: S K Mondal Made Easy Contd… Compiled by: S K Mondal Made Easy Contd…
y Ingate: A channel through which the molten metal Types of Gate or In‐gate
enters the mould cavity.
Top gate: Causes turbulence in the mould cavity, it is prone
y Vent: Small opening in the mould to facilitate escape
of air and gases. to form dross, favourable temperature gradient towards the
Compiled by: S K Mondal Made Easy 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 most
economical in preparation.
Step Gate: Used for heavy and large castings, size of ingates
are normally increased from top to bottom.Compiled by: S K Mondal Made Easy
IES 2011 IES 2011
In light metal casting, runner should be so designed that: Match List –I with List –II and select the correct answer using
1. It avoids aspiration the code given below the lists :
2. It avoids turbulence
3. The path of runner is reduced in area so that List –I List –II
unequal volume of flow through each gate
takes place A. Top gate 1. Heavy and large castings
(a) 1 and 2 only B. Bottom gate 2. Most widely used and economical
(b) 1 and 3 only
(c) 2 and 3 only C. Parting gate 3. Turbulence
(d) 1, 2 and 3
Ans. (a) D. Step gate 4. Unfavourable temperature gradient
Compiled by: S K Mondal Made Easy Codes [Ans. (a)]
A
B CD ABCD
(a) 3 4
(c) 3 2 2 1 (b) 1 4 2 3
4 1 (d) 1 2 4 3Compiled by: S K Mondal Made Easy
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IES‐1998 GATE‐2002
A sand casting mould The primary purpose of a sprue in a casting
assembly is shown in
the above figure. The mould is to
elements marked A
and B are respectively (a)Feed the casting at a rate consistent with the rate
(a) Sprue and riser of solidification
(b) Ingate and riser
(c) Drag and runner (b)Act as a reservoir for molten metal
(d) Riser and runner
Ans. (a) (c)Feed molten metal from the pouring basin to the
gate
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(d)Help feed the casting until all solidification takes
place
Ans. (c)
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The goals for the gating system IES‐1998
y To minimize turbulence to avoid trapping gasses into Which of the following are the requirements of an ideal
the mold gating system?
1. The molten metal should enter the mould cavity with as
y To get enough metal into the mold cavity before the
metal starts to solidify high a velocity as possible.
2. It should facilitate complete filling of the mould cavity.
y To avoid shrinkage 3. It should be able to prevent the absorption of air or gases
y Establish the best possible temperature gradient in the
from the surroundings on the molten metal while
solidifying casting so that the shrinkage if occurs must f lowing through it.
be in the gating system not in the required cast part. Select the correct answer using the codes given below:
y Incorporates a system for trapping the non‐metallic (a) 1, 2 and 3 (b) 1 and 2 (c) 2 and 3 (d) 1 and 3
inclusions.
Ans. (c)
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IES‐2009 Types of Gating Systems
Consider the following statements: The gating systems are of two types:
1.The actual entry point through which the molten y Pressurized gating system
metal enters the mould cavity is called ingate. y Un‐pressurized gating system
2.Bottom gate in case of a mould creates unfavourable
temperature gradient. Compiled by: S K Mondal Made Easy
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
Ans. (d)
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Pressurized Gating System Un‐Pressurized Gating System
y The total cross sectional area decreases towards the y The total cross sectional area increases towards the
mold cavity mold cavity
y Back pressure is maintained by the restrictions in the y Restriction only at the bottom of sprue
metal flow y Flow of liquid (volume) is different from all gates
y Aspiration in the gating system as the system never
y Flow of liquid (volume) is almost equal from all gates
y Back pressure helps in reducing the aspiration as the runs full
y Less turbulence.
sprue always runs full
y Because of the restrictions the metal flows at high Compiled by: S K Mondal Made Easy
velocity leading to more turbulence and chances of
mold erosion.
Compiled by: S K Mondal Made Easy
Sprue Design
y Sprue: Sprue is the channel through which the molten
metal is brought into the parting plane where it enters the
runners and gates to ultimately reach the mould cavity.
y The molten metal when moving from the top of the cope to
the parting plane gains in velocity and some low‐pressure
area would be created around the metal in the sprue.
y Since the sand mould is permeable, atmospheric air would The exact tapering can be obtained by the equation of
continuity. Denoting the top and choke sections of The sprue by
be breathed into this low‐pressure area which would then the subscripts’t’ and 'c' respectively, we get
be carried to the mould cavity.
y To eliminate this problem of air aspiration, the sprue is Vc
Vt
tapered to gradually reduce the cross section as it moves AtVt = AcVc At = Ac
away from the top of the cope as shown in Figure below (b).
Compiled by: S K Mondal Made Easy Contd… Compiled by: S K Mondal Made Easy Contd…
Since the velocities are proportional to the square of GATE‐2001
the potential heads, as can be derived from
Bernoulli's equation, The height of the down‐sprue is 175 mm and its
cross‐sectional area at the base is 200 mm2. The
At = Ac hc cross‐sectional area of the horizontal runner is
ht also 200 mm2. Assuming no losses, indicate the
correct choice for the time (in seconds) required to
fill a mould cavity of volume 106 mm3. (Use g = 10
m/s2).
Where H = actual (a)2.67 (b)8.45 (c)26.72 (d)84.50
sprue height Ans. (a)
and ht = h + H Compiled by: S K Mondal Made Easy
Compiled by: S K Mondal Made Easy
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GATE‐2007
A 200 mm long down sprue has an area of cross
section of 650 mm2 where the pouring basin meets the
down sprue (i.e. at the beginning of the down sprue).
A constant head of molten metal is maintained by the
pouring basin. The Molten metal flow rate is 6.5 × 105
mm3/s. Considering the end of down sprue to be open
to atmosphere and an acceleration due to gravity of
104mm/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)190.0 Ans. (c)
Compiled by: S K Mondal Made Easy Contd… Compiled by: S K Mondal Made Easy
Gating ratio IES‐2003
y Gating ratio is defined as: Sprue area: Runner area: A gating ratio of 1: 2: 4 is used to design the gating
Ingate area. system for magnesium alloy casting. This gating ratio
refers to the cross∙ section areas of the various gating
y For high quality steel castings, a gating ratio of 1: 2: 2 or elements as given below:
1: 2: 1.5 will produce castings nearly free from erosion, 1. Down sprue 2. Runner bar 3. Ingates
will minimize oxidation, and will produce uniform The correct sequence of the above elements in the
f low. ratio 1: 2: 4 is
(a) 1, 2 and 3
y A gating ratio of 1: 4: 4 might favour the formation of (b) 1,3 and 2
oxidation defects. (c) 2, 3 and 1
(d) 3, 1 an 2
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Ans. (a)
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IES‐2005 GATE‐2010
The gating ratio 2: 8: 1 for copper in gating system In a gating system, the ratio 1:2:4 represents
design refers to the ratio of areas of: (a) Sprue base area: runner area: ingate area
(a) Sprue: Runner: Ingate (b) Pouring basin area : ingate area : runner area
(b) Runner: Ingate: Sprue (c) Sprue base area : ingate area : casting area
(c) Runner: Sprue: Ingate (d) Runner area : ingate area : casting area
(d) Ingate: Runner: Sprue Ans. (a)
Ans. (a) Compiled by: S K Mondal Made Easy
Compiled by: S K Mondal Made Easy 16
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IAS‐1999 Risers and Riser Design
Assertion (A): The rate of flow of metal through sprue y Risers are added reservoirs designed to feed liquid
is NOT a function of the cross‐sectional areas of metal to the solidifying casting as a means of
sprue, runner and gate. compensating for solidification shrinkage.
Reason (R): If respective cross‐sectional areas of
sprue, runner and gate are in the ratio of 1: 2: 2, the y To perform this function, the risers must solidify after
system is known as unpressurised gating system. the casting.
(a) Both A and R are individually true and R is the correct
explanation of A y According to Chvorinov's rule, a good shape for a riser
(b) Both A and R are individually true but R is not the would be one that has a long freezing time (i.e., a small
correct explanation of A surface area per unit volume).
(c) A is true but R is false
(d) A is false but R is true y Live risers (also known as hot risers) receive the last
Ans. (d) hot metal that enters the mold and generally do so at a
time when the metal in the mold cavity has already
Compiled by: S K Mondal Made Easy begun to cool and solidify.Compiled by: S K Mondal Made Easy
IES‐1994 Chvorinov’s rule
Assertion (A): In a mould, a riser is designed and placed y Total solidification time (ts) = B (V/A) n
so that the riser will solidify after the casting has solidified. where n = 1.5 to 2.0
Reason (R): A riser is a reservoir of molten metal which
will supply molten metal where a shrinkage cavity would [Where, B = mould constant and is a function of (mould
have occurred. material, casting material, and condition of casting]
(a) Both A and R are individually true and R is the correct
explanation of A n = 2 and triser = 1.25 tcasting
(b) Both A and R are individually true but R is not the
correct explanation of A or ⎛ V 2 = 1.25 ⎛ V 2
(c) A is true but R is false A ⎝⎜ A
(d) A is false but R is true ⎝⎜ ⎞ ⎞
⎟⎠riser ⎠⎟casting
Ans. (a)
For cylinder V = πD2H / 4
Compiled by: S K Mondal Made Easy of diameter D
and height H ( )A = πDH + 2 πD2 4
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IES 2011 IES‐1998
The relationship between total freezing time t, A spherical drop of molten metal of radius 2 mm
volume of the casting V and its surface area A, was found to solidify in 10 seconds. A similar drop
according to Chvorinov’s rule is : of radius 4 mm would solidify in
(a) t = k ⎛V ⎞
⎜⎝ A ⎟⎠
(b ) t = k ⎛A ⎞ (a) 14.14 seconds
⎝⎜ V ⎠⎟
(c) t = k ⎛A ⎞2 (b) 20 seconds
⎜⎝ V ⎠⎟
(d ) t = k ⎛V ⎞2 (c) 28.30 seconds
Where K i⎝⎜s Aa c⎠⎟onstant [Ans. (d)] (d) 40 seconds [Ans. (d)]
Compiled by: S K Mondal Made Easy Compiled by: S K Mondal Made Easy
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GATE‐2003 IES‐2006
With a solidification factor of 0.97 x 106 s/m2, the According to Chvorinov's equation, the
solidification time (in seconds) for a spherical solidification time of a casting is proportional to:
casting of 200 mm diameter is
(a) 539 (b) 1078 (c) 4311 (d) 3233 (a) v2
[Ans. (b)] (b) v
Compiled by: S K Mondal Made Easy (c) 1/v
(d) 1/v2
Where, v = volume of casting [Ans. (a)]
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GATE‐2007
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 and of same material. They are being cast. The
ratio of the solidification time of the cube to the same
of the sphere is:
(a) ⎛ 4π 3 ⎛ r 6 (b ) ⎛ 4π ⎞⎛ r 2 (c ) ⎛ 4π 2 ⎛ r 3 (d ) ⎛ 4π 2 ⎛ r 4
⎝⎜ 6 ⎟⎠ ⎜⎝ l ⎜⎝ 6 ⎝⎜ l ⎝⎜ 6 ⎝⎜ l
⎞ ⎞ ⎞ ⎞ ⎞ ⎞ ⎞
⎝⎜ 6 ⎠⎟ ⎜⎝ l ⎠⎟ ⎠⎟ ⎠⎟ ⎟⎠ ⎟⎠ ⎟⎠
Ans. (d) Compiled by: S K Mondal Made Easy
Compiled by: S K Mondal Made Easy
Conventional Question ESE 2003: Modulus Method
Compare the solidification time of two y It has been empirically established that if the modulus
optimum side – risers of the same volume of the riser exceeds the modulus of the casting by a
with one has cylindrical shape and other is factor of 1.2, the feeding during solidification would be
parallopiped. satisfactory.
[30 Marks]
MR = 1.2 Mc
Compiled by: S K Mondal Made Easy y Modulus = volume/Surface area
y In steel castings, it is generally preferable to choose a
riser with a height‐to‐diameter ratio of 1. Contd…
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π D2 +π D2 Conventional Question IES‐2008
4
y Calculate the size of a cylindrical riser (height and diameter
Compiled by: S K Mondal Made Easy equal) necessary to feed a steel slab casting of dimensions
30 x 30 x 6 cm with a side riser, casting poured horizontally
into the mould.
[Use Modulus Method]
[10 ‐ Marks]
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Caine’s Method Table: Constants in Caine’s Method
Freezing ratio = ratio of cooling characteristics of casting to Compiled by: S K Mondal Made Easy
the riser. (( ))x =A V casting
A V riser
The riser should solidify last so x > 1
According to Caine X = Y a b + c
−
Y = V V c a rsi st ei nr g and a, b, c are constant.
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Conventional Question IES‐2007 Chills
y Calculate the size of a cylindrical riser (height and y External chills are masses of high‐heat‐capacity, high‐thermal‐
diameter equal) necessary to feed a steel slab conductivity material that are placed in the mould (adjacent to
casting of dimensions 25 x 25 x 5 cm with a side the casting) to accelerate the cooling of various regions.
riser, casting poured horizontally into the mould.
[Use Caine’s Method] Chills can effectively promote directional solidification or
increase the effective feeding distance of a riser. They can often
Compiled by: S K Mondal Made Easy be used to reduce the number of risers required for a casting.
y Internal chills are pieces of metal that are placed within the
mould cavity to absorb heat and promote more rapid
solidification. Since some of this metal will melt during the
operation, it will absorb not only the heat‐capacity energy, but
also some heat of fusion. Since they ultimately become part of
the final casting, internal chills must be made from the same
alloy as that being cast.
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IES‐1995 GATE‐1998,2007
Directional solidification in castings can be improved Chills are used in moulds to
by using (a) Achieve directional solidification
(a) Chills and chaplets (b) Reduce the possibility of blowholes
(b) Chills and padding (c) Reduce freezing time
(c) Chaplets and padding (d) Smoothen metal flow for reducing splatter
(d) Chills, chaplets and padding
[Ans. (a)]
[Ans. (b)]
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Compiled by: S K Mondal Made Easy
IAS 1994 Cupola
Chills are used in casting moulds to y Steel can be melted in hot blast cupola.
(a) Achieve directional solidification y In hot blast cupola, the flue gases are used to preheat
(b) Reduce possibility of blow holes
(c) Reduce the freezing time the air blast to the cupola so that the temperature in
(d) Increase the smoothness of cast surface the furnace is considerably higher than that in a
conventional cupola.
Ans. (a) y Cupola has been the most widely used furnace for
melting cast iron.
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Compiled by: S K Mondal Made Easy
IES‐1997 Electric Arc Furnace
Assertion (A): Steel can be melted in hot blast cupola. y For heavy steel castings, the open‐hearth type of
furnaces with electric arc or oil fired would be generally
Reason (R): In hot blast cupola, the flue gases are used to suitable in view of the large heat required for melting.
preheat the air blast to the cupola so that the temperature in
the furnace is considerably higher than that in a y Electric arc furnaces are more suitable for ferrous
conventional cupola. materials and are larger in capacity.
(a) Both A and R are individually true and R is the correct Compiled by: S K Mondal Made Easy
explanation of A
(b) Both A and R are individually true but R is not the
correct explanation of A
(c) A is true but R is false
(d) A is false but R is true [Ans. (a)]
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Crucible Furnace Ladles
y Smaller foundries generally prefer the crucible furnace.
y The crucible is generally heated by electric resistance y Two types of ladles used in the pouring of castings.
or gas flame. Compiled by: S K Mondal Made Easy
Induction Furnace
y The induction furnaces are used for all types of
materials, the chief advantage being that the heat
source is isolated from the charge and the slag and flux
get the necessary heat directly from the charge instead
of the heat source.
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Casting Cleaning (fettling) GATE‐1996
Impurities in the molten metal are prevented from Light impurities in the molten metal are prevented
reaching the mould cavity by providing a from reaching the mould cavity by providing a
(i) Strainer (a) Strainer
(ii) Button well (b) Button well
(iii) Skim bob (c) Skim bob
(d) All of the above
Compiled by: S K Mondal Made Easy Ans. (c)
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Pouring time GATE‐2005
Time taken to fill the mould with top gate A mould has a downsprue whose length is 20 cm
and the cross sectional area at the base of the
tA = A.H Where A = Area of mould downsprue is 1cm2. The downsprue feeds a
Ag 2ghm H = Height of mould horizontal runner leading into the mould cavity of
Ag = Area of Gate volume 1000 cm3. The time required to fill the
Hm = Gate height mould cavity will be
(a)4.05 s (b)5.05 s (c)6.05 s (d)7.25 s
Time taken to fill the mould with bottom gate Ans. (b)
2A Compiled by: S K Mondal Made Easy
Ag 2g
( )tB
= hm − hm − H
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GATE‐2006 Expression for choke area
In a sand casting operation, the total liquid head is
m
maintained constant such that it is equal to the mould CA = 2gH mm2
height. The time taken to fill the mould with a top gate cρt
is tA. If the same mould is filled with a bottom gate, Where m = mass of the casting, kg
then the time taken is tB. Ignore the time required to ρ = Density of metal, kg / m3
fill the runner and frictional effects. Assume t = pouring time
c = Efficiency factor and is the function of gate
atmospheric pressure at the top molten metal surfaces.
system used
The relation between tA and tB is H = Effective head of liquid metal
= h for top gate
(A) tB = 2 tA
(B) tB = 2 tA
(C) tB = tA Ans. (b)
2
(D) t = 2 2 tB ComApiled by: S K Mondal Made Easy Compiled by: S K Mondal Made Easy Contd…
H=h‐ hm for bottom gate Casting Defects
2
The following are the major defects, which are likely to
=h‐ hc2 for parting line gate occur in sand castings:
2hm y Gas defects
y Shrinkage cavities
hC hm hm y Molding material defects
hm y Pouring metal defects
y Mold shift.
P i li
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top gate parting line gate bottom gate
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Gas Defects Shrinkage Cavities
y A condition existing in a casting caused by the y These are caused by liquid shrinkage occurring during the
trapping of gas in the molten metal or by mold gases solidification of the casting.
evolved during the pouring of the casting.
y To compensate for this, proper feeding of liquid metal is
y The defects in this category can be classified into required. For this reason risers are placed at the
blowholes and pinhole porosity. appropriate places in the mold.
y Blowholes are spherical or elongated cavities present y Sprues may be too thin, too long or not attached in the
in the casting on the surface or inside the casting. proper location, causing shrinkage cavities.
y Pinhole porosity occurs due to the dissolution of y It is recommended to use thick sprues to avoid shrinkage
hydrogen gas, which gets entrapped during heating of cavities.
molten metal.
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Compiled by: S K Mondal Made Easy
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Molding Material Defects Cut and washes
y Cuts and washes, y These appear as rough spots and areas of excess metal, and
y Scab are caused by erosion of molding sand by the flowing
y Metal penetration, metal.
y Fusion, and
y Swell y This is caused by the molding sand not having enough
strength and the molten metal flowing at high velocity.
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y The former can be taken care of by the proper choice of
molding sand and the latter can be overcome by the
proper design of the gating system.
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Scab Metal penetration
y This defect occurs when a portion of the face of a mould y When molten metal enters into the gaps between sand
lifts or breaks down and the recess thus made is filled by grains, the result is a rough casting surface.
metal.
y This occurs because the sand is coarse or no mold wash was
y When the metal is poured into the cavity, gas may be applied on the surface of the mold. The coarser the sand
disengaged with such violence as to break up the sand, grains more the metal penetration.
which is then washed away and the resulting cavity filled
with metal. Compiled by: S K Mondal Made Easy
y The reasons can be: ‐ too fine sand, low permeability of
sand, high moisture content of sand and uneven mould
ramming.
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Fusion Swell
y This is caused by the fusion of the sand grains with Under the influence of metallostatic forces, the mold
the molten metal, giving a brittle, glassy appearance wall may move back causing a swell in the dimension
on the casting surface. of the casting. A proper ramming of the mold will
correct this defect.
y The main reason for this is that the clay or the sand
particles are of lower refractoriness or that the Inclusions
pouring temperature is too high.
Particles of slag, refractory materials sand or
Compiled by: S K Mondal Made Easy deoxidation products are trapped in the casting during
pouring solidification. The provision of choke in the
gating system and the pouring basin at the top of the
mold can prevent this defect
Compiled by: S K Mondal Made Easy
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Pouring Metal Defects y The mis‐run and cold shut defects are caused either by
a lower fluidity of the mold or when the section
The likely defects in this category are thickness of the casting is very small. Fluidity can be
y Mis‐runs and improved by changing the composition of the metal
y Cold shuts and by increasing the pouring temperature of the
metal.
y A mis‐run is caused when the metal is unable to fill
the mold cavity completely and thus leaves unfilled Compiled by: S K Mondal Made Easy
cavities.
y A cold shut is caused when two streams while meeting
in the mold cavity, do not fuse together properly thus
forming a discontinuity in the casting.
Compiled by: S K Mondal Made Easy Contd…
GATE‐2004 GATE‐2009
Misrun is a casting defect which occurs due to Two streams of liquid metal which are not hot
(a) Very high pouring temperature of the metal enough to fuse properly result into a casting defect
(b) Insufficient fluidity of the molten metal known as
(c) Absorption of gases by the liquid metal
(d) Improper alignment of the mould flasks (a) Cold shut
Ans. (b)
(b) Swell
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(c) Sand wash
(d) Scab [Ans. (a)]
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Mold Shift IES‐2001
The mold shift defect occurs when cope and drag Scab is a
or molding boxes have not been properly aligned. (a) Sand casting defect
(b) Machining defect
Compiled by: S K Mondal Made Easy (c) Welding defect
(d) Forging defect
Ans. (a)
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IAS‐2004 GATE‐2003
Match List‐I (Casting Defects) with List‐II (Explanation) and select the correct Hardness of green sand mould increases with
answer using the codes given below the lists: (a) Increase in moisture content beyond 6 percent
(b) Increase in permeability
List‐I List‐II (c) Decrease in permeability
(d) Increase in both moisture content and
(Casting Defects) (Explanation) permeability
A. Metallic projections 1. Consist of rounded or rough internal or exposed cavities Ans. (c)
including blow holes and pin holes
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B. Cavities 2. Formed during melting, solidification and moulding.
C. Inclusions 3. Includes single folds, laps, scars adhering sand layers and
oxide scale
D. Discontinuities 4. Include cracks, cold or hot tearing and cold shuts
5.Consist of fins, f lash 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)
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IES‐1998 IES‐2005
Assertion (A): Stiffening members, such as webs In gating system design, which one of the
and ribs, used on a casting should be liberally following is the correct sequence in which choke
provided. area, pouring time, pouring basin and sprue sizes
are calculated?
Reason (R): They will provide additional strength
to a cast member. (a) Choke area ‐ Pouring time ‐ Pouring basin – Sprue
(a) Both A and R are individually true and R is the (b) Pouring basin ‐ Sprue ‐ Choke area ‐ Pouring time
correct explanation of A
(c) Choke area ‐ Sprue ‐ Pouring basin ‐ Pouring time
(b) Both A and R are individually true but R is not the
correct explanation of A (d) Pouring basin ‐ Pouring time ‐ Choke area ‐ Sprue
(c) A is true but R is false
(d) A is false but R is true [Ans. (a)] Ans. (a)
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IES‐1997 IES‐2009
If the melting ratio of a cupola is 10: 1, then the In which one of the following furnaces most of the
coke requirement for one ton melt will be non‐ferrous alloys are melted?
(a) 0.1 ton (a) Reverberatory furnace
(b) 10 tons (b) Induction furnace
(c) 1 ton (c) Crucible furnace
(d) 11 tons (d) Pot furnace
Ans. (a) Ans. (d)
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IAS‐2001 IAS‐2004
Which of the following pattern‐materials are used Which one of the following gating systems is best
in Precision Casting? suited to obtain directional solidification?
1. Plaster of Paris (a) Top grating
2. Plastics (b) Part‐line grating
3. Anodized Aluminium Alloy (c) Bottom grating
4. Frozen Mercury (d) Stepped grating
Select 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. (d)
Ans. (b)
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Compiled by: S K Mondal Made Easy
Cast Aluminium Code Cast Aluminium Code Contd..
y Four digit identification system y Second two digits identify the aluminium alloy or
y First digit indicates alloy group indicate the aluminium purity.
1 – Aluminium, 99% or more y The last digit is separating from the other three by a
2 – copper decimal point and indicates the product form; that is,
3 – Silicon, with copper and/or magnesium castings or ingots
4 – silicon
5 – magnesium y A modification of the original alloy is indicated by a
6 – not used serial letter before the numerical designation.
7 – zinc
8 – tin y Alloy A514.0 indicates an aluminium alloy casting with
9 – other elementsCompiled by: S K Mondal Made Easy magnesium as the principal alloy. One modification to
the original alloy has made, as indicated by the letter A.
Compiled by: S K Mondal Made Easy
IES 2011 casting A514.0
In the designation of Aluminium
indicates :
(a) Aluminium purity
(b) Aluminium content
(c) Percentage of alloy element
(d) Magnesium Content
Ans. (d)
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Special Casting Shell Moulding
By S K Mondal y The sand is mixed with a thermosetting resin is
allowed to come in contact with a heated metal pattern
(2000C).
y A skin (shell) of about 3.5 mm of sand and plastic
mixture adhere to the pattern.
y Then the shell is removed from the pattern.
y The cope and drag shells are kept in a flask with
necessary backup material and the molten metal is
poured into the mold.
y Can produce complex parts.
y A good surface finish and good size tolerance
reduce the need for machining.
y Materials can be cast: CI, Al and Cu alloys.
Shell moulding process
Molding Sand in Shell Molding y Hot coating: the mixture is heated to 150oC– 180oC prior
to loading the sand. In the course of sand mixing, the
y The molding sand is a mixture of fine grained quartz sand soluble phenol formaldehyde resin is added. The mixer is
allowed to cool up to 80 – 90o C. Hot coting gives better
and powdered bakelite. properties to the mixtures than cold method.
y Cold coating and Hot coating methods are used for
coating the sand grains with bakelite.
y 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…
1
10/9/2011
Advantages Limitations
y Dimensional accuracy. y Expensive pattern
y Smoother surface finish. (Due to finer size grain used) y Small size casting only.
y Very thin sections can be cast. y Highly complicated shapes cannot be obtained.
y Very small amount of sand is needed. y More sophisticated equipment is needed for handling
the shell moldings.
Applications IES 2010
y Cylinders and cylinder heads for air‐ cooled IC Consider the following advantages of shell
engines mould casting:
1. Close dimensional tolerance.
y Automobile transmission parts. 2. Good surface finish.
y Piston rings 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‐1996 IES‐2005
Consider the following ingredients used in In shell moulding, how can the shell thickness
moulding: be accurately maintained?
1. Dry silica sand (a) By controlling the time during which the pattern
is in contact with mould
2.Clay
(b) By controlling the time during which the pattern
3.Phenol formaldehyde is heated
4.Sodium silicate (c) By maintaining the temperature of the pattern in
the range of 175oC – 380oC
Those used for shell mould casting include
(d) By the type of binder used
(a) 1, 2 and 4 (b) 2, 3 and 4
(c) 1and 3 (d) 1, 2, 3 and 4
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IES‐2006 IES 2007
Shell moulding can be used for: Which of the following are employed in shell
(a) Producing milling cutters moulding?
(b) Making gold ornaments
(c) Producing heavy and thick walled casting 1. Resin binder 2. Metal pattern 3. Heating coils
(d) Producing thin casting
Select the correct answer using the code given
below:
(a) 1 and 2 only (b) 1 and 3 only
(c) 2 and 3 only (d) 1, 2 and 3
IAS‐2007 IAS‐1999
The mould in shell moulding process is made up Match List I (Moulding Process) with List II (Binding
of which of the following? Agent) and select the correct answer using the codes
(a) Gypsum + setting agents given below the lists:
(b) Green sand + clay
(c) Sodium silicate + dried sand List I List II
(d) Dried silica + phenolic resin
A. Green sand 1. Silicate
B. Core sand 2. Organic
C. Shell moulding 3. Clay
D. CO2 process 4. Plaster of Paris
5. Plastic
Codes:A B C D A BC D
(a) 3 2 5 1 (b) 3 2 4 1
(c) 2 3 5 4 (d) 2 3 4 5
Investment Casting
Investment casting process or lost wax process
Basic steps:
1. Produce expendable wax, plastic, or polystyrene patterns.
2. Assemble these patterns onto a gating system
3. Investing or covering the pattern assembly with refractory
slurry
4. Melting the pattern assembly to remove the pattern material
5. Firing the mould to remove the last traces of the pattern
material
6. Pouring molten metal
7. Knockout, cutoff and finishing.
Fig. Investment f lask‐casting procedure
3
10/9/2011
Ceramic Shell Investment Casting
y In ceramic shell investment casting a ceramic shell is
built around a tree assembly by repeatedly dipping a
pattern into a slurry (refractory material such as
zircon with binder).
y After each dipping and stuccoing is completed, the
assembly is allowed to thoroughly dry before the next
coating is applied.
IES 2009
y 2 marks
Advantages Limitations
y Tight dimensional tolerances y Costly patterns and moulds
y Excellent surface finish (1.2 to 3.0 μm ) y Labour costs can be high
y Machining can be reduced or completely y Limited size
eliminated
y High melting point alloy can be cast, almost any
metal can be cast
y Almost unlimited intricacy
4
Applications 10/9/2011
y Aerospace and rocket components. IES 2011
y Vanes and blades for gas turbines.
y Surgical instruments The proper sequence of investment casting steps is :
(a) Slurry coating – pattern melt out‐Shakeout – Stucco
GATE‐2006 coating
(b) Stucco coating – Slurry coating – Shakeout – Pattern
An expendable pattern is used in melt out
(a) Slush casting (c) Slurry coating – Stucco coating – Pattern melt out –
(b) Squeeze casting Shakeout
(c) Centrifugal casting (d) Stucco coating – Shakeout – Slurry coating – Pattern
(d) Investment casting melt out
IES‐1992
The most preferred process for casting gas turbine
blades is:
(a) Die moulding
(b) Shell moulding
(c) Investment moulding
(d) Sand casting
JWM 2010 IES 2010
Consider the following materials : Assertion (A): These investment casting is used for
precision parts such as turbine plates, sewing
1. Wax machines etc.
2. Wood Reason (R): The investment castings have a good
surface finish and are exact reproductions of the
3. Plastic master pattern.
Which of these materials can be used as pattern in (a) Both A and R are individually true and R is the
investment casting process ? correct explanation of A
(a) 1, 2 and 3 (b) 1 and 2 only (b) Both A and R are individually true but R is NOT the
correct explanation of A
(c) 2 and 3 only (d) 1 and 3 only
(c) A is true but R is false
(d) A is false but R is true
5
10/9/2011
IES 2007 IES‐2006
Consider the following statements in respect of Which of the following materials are used for
investment castings: making patterns in investment casting method?
1. The pattern or patterns is/are not joined to a stalk or 1. Wax 2. Rubber 3. Wood 4. Plastic
sprue also of wax to form a tree of patterns.
2.The prepared moulds are placed in an oven and heated Select the correct answer using the codes given below:
gently to dry off the invest and melt out the bulk of wax.
(a) Only 1 and 3 (b) Only 2 and 3
3.The moulds are usually poured by placing the moulds in
a vacuum chamber. Which of the statements given above (c) Only 1, 2 and 4 (d) Only 2, 3 and 4
are correct?
(a) 1 and 2 only (b) 1 and 3 only
(c)2 and 3 only (d) 1, 2 and 3
IAS‐1996 Permanent Mould Casting
Light and intricate parts with close dimensional y The process in which we use a die to make the
tolerances of the order of ± 0.005 mm are castings is called permanent mold casting or gravity
produced by die casting, since the metal enters the mold under
(a) Investment casting gravity.
(b) Die casting
(c) Centrifugal casting y Some time in die‐casting we inject the molten metal
(d) Shell mould casting with a high pressure. When we apply pressure in
injecting the metal it is called pressure die casting
process.
y Grey cast iron is used for mould material.
Advantages Disadvantages
y Good surface finish and dimensional accuracy y High initial mold cost
y Metal mold gives rapid cooling and fine‐grain y Shape, size, and complexity are limited
y Mold life is very limited with high‐melting‐point
structure
y Multiple‐use molds. metals such an steel.
y Low melting point metals can be cast
‐ Aluminum
‐ Zinc
‐ Magnesium alloys
‐ Brass
‐ Cast iron
6
Applications 10/9/2011
y Pistons/cylinders/rods Die Casting
y Gears
y Kitchenware y Molten metal is injected into closed metal dies under
pressures ranging from 100 to 150 MPa.
Video
y Pressure is maintained during solidification
y After which the dies separate and the casting is ejected
along with its attached sprues and runners.
y Cores must be simple and retractable and take the
form of moving metal segments
Die casting machines can be
y Hot chamber
y Cold chamber
Hot chamber machines are
y Good for low temperature (approx. 400°C)
y Faster than cold chamber machines
y Cycle times must be short to minimize metal
contamination
y Metal starts in a heated cylinder
y A piston forces metal into the die
y The piston retracts, and draws metal in
y Metal: Lead, Tin, Zinc
Hot Chamber
7
10/9/2011
Cold chamber machines
y Casts high melting point metals ( > 600°C)
y High pressures used
y Metal is heated in a separate crucible
y Metal is ladled into a cold chamber
y The metal is rapidly forced into the mold before it
cools
y Copper, Brass and Aluminium can cast.
Advantages
y Extremely smooth surfaces (1 µm)
y Excellent dimensional accuracy
y Rapid production rate
y Better mechanical properties compared to sand
casting
y Intricate parts possible
y Minimum finishing operations
y Thin sections possible
Limitations ¾Applications
y Carburettors
y High initial die cost y Automotive parts
y Limited to high‐fluidity nonferrous metals y Bathroom fixtures
y Part size is limited y Toys
y Porosity may be a problem
y Some scrap in sprues, runners, and flash, but this can ¾Common metals
y Alloys of aluminum, zinc, magnesium, and lead
be directly recycled y Also possible with alloys of copper and tin
8
10/9/2011
IES 2011 IES‐2009
Consider the following advantages of die casting over Which of the following are the most suitable
sand casting : materials for die casting?
1. Rapidity of the process (a) Zinc and its alloys
2. Smooth surface (b) Copper and its alloys
3. Strong dense metal structure (c) Aluminium and its alloys
Which of these advantages are correct ? (d) Lead and its alloys
(a) 1, 2 and 3
(b) 1 and 2 only
(c) 2 and 3 only
(d) 1 and 3 only
JWM 2010 IES‐2005
Assertion (A) : In die casting method, small Which one of the following processes produces a
thickness can be filled with liquid metal. casting when pressure forces the molten metal
into the mould cavity?
Reason (R) : The air in die cavity trapped inside the
casting causes problems. (a) Shell moulding (b) Investment casting
(a) Both A and R are individually true and R is the (c) Die casting (d) Continuous casting
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‐2006 IES‐1995
In which of the following are metal moulds used? Assertion (A): An aluminium alloy with 11 % silicon is
(a) Greensand mould used for making engine pistons by die casting
(b) Dry sand mould technique.
(c) Die casting process
(d) Loam moulding Reason (R): Aluminium has low density and addition
of silicon improves its fluidity and therefore its
castability.
(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
9
10/9/2011
IES‐1995 IAS‐2007
Match List I with List II and select the correct answer taking the help Consider the following statements:
of codes given below the lists: 1. Zinc die castings have low strength.
2. In the die casting process, very thin sections or
List I List II complex shapes can be obtained easily.
Which of the statements given above is/are correct?
(Products) (Process of manufacture) (a) 1 only
(b) 2 only
A. Automobile piston in aluminium alloy 1. Pressure die‐casting (c) Both 1 and 2
(d) Neither 1 nor 2
B. Engine crankshaft in spheroidal
graphite iron 2. Gravity die‐casting
C. Carburettor housing in aluminium alloy 3. Sand casting
D. Cast titanium blades 4. Precision investment
casting
5. Shell moulding
Code: A B C D ABCD
(a) 2 3 1 5 (b) 3 2 1 5
(c) 2 1 3 4 (d) 4 1 23
IAS‐1996 IES 2011
Assertion (A): Die casting yields a product of good Consider the following statements :
accuracy and finish.
1. Hot chamber machine is used for casting zinc, tin and
Reason (R): Low melting alloys used in die other low melting alloys.
casting.
2. Cold chamber machine is used for die casting of
(a) Both A and R are individually true and R is the ferrous alloys
correct explanation of A
3. Rapid cooling rate in die casting produces high
(b) Both A and R are individually true but R is not the strength and quality in many alloys.
correct explanation of A
Which of these statements are correct?
(c) A is true but R is false
(a) 1, 2 and 3 (b) 1 and 2 only
(d) A is false but R is true
(c) 2 and 3 only (d) 1 and 3 only
GATE‐2007 IES‐1995
Which of the following engineering materials is Assertion (A): Aluminium alloys are cast in hot
the most suitable candidate for hot chamber die chamber die casting machine.
casting? Reason (R): Aluminium alloys require high melting
(a) Low carbon steel when compared to zinc alloys.
(b) Titanium (a) Both A and R are individually true and R is the correct
(c) Copper explanation of A
(d) Tin (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
10
10/9/2011
Centrifugal Casting Fig. True centrifugal casting
y Process: 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
y A mold is set up and rotated along a vertical (rpm is
reasonable), or horizontal (200‐1000 rpm is reasonable)
axis.
y The mold is coated with a refractory coating.
y During cooling lower density impurities will tend to rise
towards the center of rotation.
Properties
y The mechanical properties of centrifugally cast jobs are
better compared to other processes, because the inclusions
such as slag and oxides get segregated towards the centre
and can be easily removed by machining. Also, the
pressure acting on the metal throughout the solidification
causes the porosity to be eliminated giving rise to dense
metal.
y No cores are required for making concentric holes in the
case of true centrifugal casting.
Advantages Limitations
y Fine grained structure at the outer surface of the y More segregation of alloy component during pouring under
casting free of gas and shrinkage cavities and the forces of rotation
porosity
y Contamination of internal surface of castings with non‐
y Formation of hollow interiors in cylinders without metallic inclusions
cores
y Inaccurate internal diameter
y Can produce a wide range of cylindrical parts, y Shape is limited.
including ones of large size. y Spinning equipment can be expensive
y Poor machinability
y Good dimensional accuracy, soundness, and
cleanliness
y There is no need for gates and runners, which
increases the casting yield, reaching almost 100 %.
11
Common metals 10/9/2011
y Iron GATE‐2002
y steel
y stainless steel In centrifugal casting, the impurities are
y alloys of aluminium, copper, and nickel (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‐1993 IES‐2008
Centrifugally cast products have Which of the following casting processes does not
(a) Large grain structure with high porosity /do not require central core for producing pipe?
(b) Fine grain structure with high density 1. Sand casting process
(c) Fine grain structure with low density 2. Die casting process
(d) Segregation of slug towards the outer skin of the 3. Centrifugal casting process
casting Select the correct answer using the code given below:
(a) 1 and 2
(b) 2 only
(c) 2 and 3
(d) 3 only
IES‐2009 IES 2007
Which one of the following casting processes is Which one of the following is the correct
best suited to make bigger size hollow statement?
symmetrical pipes? In a centrifugal casting method
(a) Die casting (a) No core is used
(b) Investment casting (b) Core may be made of any metal
(c) Shell moulding (c) Core is made of sand
(d) Centrifugal casting (d) Core is made of ferrous metal
12
10/9/2011
IES‐1998 IES‐2009
Poor machinability of centrifugally cast iron pipe Which of the following are the most likely
is due to characteristics in centrifugal casting?
(a) Chilling (a) Fine grain size and high porosity
(b) Segregation (b) Coarse grain size and high porosity
(c) Dense structure (c) Fine grain size and high density
(d) High mould rotation speed (d) Coarse grain size and high density
IES 2007 IES‐2000
Match List I with List II and select the correct answer using the code given Match List I (Process) with List II (Products/materials)
below the Lists: and select the correct answer using the codes given
below the Lists:
List I List II
(Casting Process) (Principle)
A. Die casting 1.The metal solidifies in a rotating mould List I List II
B. Investment casting 2.The pattern cluster is repeatedly dipped A. Die casting 1. Phenol formaldehyde
into a ceramic slurry and dusted with
refractory B. Shell molding 2. C.I. pipes
C. Shell moulding 3. Molten metal is forced by pressure into C. CO2 molding 3. Non‐ferrous alloys
a metallic mould D. Centrifugal casting 4. Sodium silicate
D. Centrifugal casting 4. After cooling, the invest is removed
from the Casting by pressure jetting or
vibratory cleaning Codes:A B C D A B C D
Code: A B C D ABCD (a) 1 3 4 2 (b) 3 1 4 2
(a) 2 1 3 4 (b) 3 4 2 1
(c) 2 4 3 1 (c) 3 1 24 (c) 3 1 2 4 (d) 1 3 2 4
IAS‐2004 Semi‐centrifugal Casting
Match List‐I (Name of the Process) with List‐II (Advantage) and select the correct y Centrifugal force assists the flow of metal from a
answer using the codes given below the lists: central reservoir to the extremities of a rotating
symmetrical mold, which may be either expendable or
List‐I List‐II multiple‐use
(Name of the Process) (Advantage) y Rotational speeds are lower than for true centrifugal
casting
A. Sand Casting 1. Large cylindrical parts with good quality
y Cores can be used to increase the complexity of the
B. Ceramic mold casting 2.Excellent dimensional accuracy and surface product.
finish
C. Die casting 3. Intricate shapes and close tolerance parts
D. Centrifugal casting 4. Almost any metal is cast and there if no limit to
size, shape and weight
5. Good dimensional accuracy, finish and low
porosity
Codes:A B C D A B C D
3
(a) 2 3 5 1 (b) 4 1 2
(c) 2 1 5 3 (d) 4 3 2 1
13
10/9/2011
IAS‐2003
Assertion (A): Semi‐centrifugal casting process is
similar to true centrifugal casting except that the
central core is used in it to form inner surface.
Reason (R): In semi‐centrifugal casting process the
axis of spin is always vertical
(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
Fig. Semi‐centrifugal casting
Centrifuging
y Uses centrifuging action to force the metal from a central
pouring reservoir into separate mold cavities that are
offset from the axis of rotation.
y Low speed
y May used to assist in the pouring of investment casting
trees.
Fig. Method of casting by the centrifuging process
IES‐2000 Dry Sand Molding
Match List I (Type of casting) with List II (Working principles) y To reduce gas forming materials air dried mould used.
and select the correct answer using the codes given below the Types:
Lists:
1.Skin drying and
List I List II 2.Complete mold drying
A. Die casting 1. Molten metal is forced into the die
under pressure
B. Centrifugal casting 2. Axis of rotation does not coincide with
axis of mould
C. Centrifuging 3. Metal solidifies when mould is rotating
D. Continuous casting 4. Continuously pouring molten metal
into mould
Codes: 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
14
10/9/2011
Slush Casting IAS‐2004
y Slush casting is a variation of the permanent mold process Which of the following are produced by slush
in which the metal is permitted to remain in the mold only casting?
until a shell of the desired thickness has formed. (a) Hollow castings with thick walls
(b) Hollow castings with thin walls
y The mold is then inverted and the remaining liquid is (c) Thin castings
poured out. (d) Thick castings
y When the mold halves are separated, the resulting casting
is a hollow shape with good surface detail but variable wall
thickness.
y Frequently used to cast low‐melting‐temperature metals
into ornamental objects such as candlesticks, lamp bases,
and statuary.
IES 2011 Squeeze Casting
The method of casting for producing ornamental pieces Process:
are: 1. Molten metal is poured into an open face die.
2. A punch is advanced into the die, and to the metal.
(a) Slush and gravity casting 3.Pressure (less than forging) is applied to the punch
(b) Pressed and slush casting and die while the part solidifies.
4.The punch is retracted, and the part is knocked out
(c) Gravity and semi permanent mould casting
with an ejector pin.
(d) Semi permanent mould and pressed casting y Overcomes problems with feeding the die, and
produces near net, highly detailed parts.
IAS‐2002 Single Crystal Casting
Match List I (Casting Process) with List II The process is effectively:
(Applications) and select the correct answer using the
codes given below the Lists: 1. Prepare a mold so that one end is a heated oven, and
the other end chilled. The part should be oriented so
List I List II that the cooling happens over the longest distance.
(Casting Process) (Applications) 2. Cast metal into the mold
A. Centrifugal casting 1. Carburetor 3. Solidification will begin at the chill plate. These
dendrites will grow towards the heated end of the
B. Squeeze casting 2. Pipes part as long dendritic crystals. The part is slowly
pulled out of the oven, past the chill plate.
C. Die Casting 3. Wheels for
automobiles 4. Remove the solidified part.
4. Gear housings
Codes: A B C ABC
(a) 2 3 1 (b) 4 1 3
(c) 2 1 3 (d) 4 3 1
15
10/9/2011
IES 2009
y Creep and thermal shock resistance properties.
2 marks
Plaster Casting Pit Moulding
y Process: A slurry of plaster, water, and various additives is y This method is used for very large castings and is done on
additives is pouted over a pattern and allowed to set. The the foundry floor.
pattern is removed and the mould is baked to remove
excess water. After pouring and solidification, the mould is
broken and the casting is removed.
y Advantage: High dimensional accuracy and smooth
surface finish, thin sections and intricate detail can
produce.
y Limitations: Lower‐temperature nonferrous metals only:
y Common metals: Primarily aluminium and copper
IES‐1996 Loam Moulding
Which of the following pairs are correctly matched? y Moulding loam is generally artificially composed of
1. Pit moulding ..................For large jobs. common brick‐clay, and sharp sand.
2. Investment moulding ... Lost wax process.
3. Plaster moulding ……… Mould prepared in y Loam means mud.
gypsum. y Loam Moulding is restricted to forms which cannot be
(a) 1, 2 and 3 (b) 1 and 2
(c) 1 and 3 (d) 2 and 3 cast conveniently in any other process.
y It is costly.
16
10/9/2011
IES‐1997 GATE‐1998
Which one of the following pairs is not correctly List I List II
matched? (A) Sand casting (1) Symmetrical and
(a) Aluminium alloy piston …………Pressure die casting circular shapes only
(b) Jewellery……………………….. Lost wax process (B) Plaster mould casting (2) Parts have hardened
(c) Large pipes ……………………..Centrifugal casting skins and soft interior
(d) Large bells ………………………Loam moulding (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‐1992 GATE‐1996
Match the following moulding/casting processes with List I List II
the product:
(A) Rivets for aircraft body 1. Forging
Moulding/Casting processes Product
(B) Carburettor body 2. Cold heading
(A) Slush casting (P) Turbine blade
(B) Shell moulding (Q) Machine tool bed (C) Crankshafts 3. Aluminium‐based
alloy
(C) Dry sand moulding (R) Cylinder block
(D) Centrifugal casting (S) Hollow castings (D) Nails 4. Pressure die casting
like lamp shades
5. Investment casting
(T) Rain water pipe
(U) Cast iron shoe
brake
IES‐2003 IES‐1993
Match List I (Products) with List II (Casting Process) and select Match the items of List I (Equipment) with the items
the correct answer using the codes given below the Lists: of List II (Process) and select the correct answer using
the given codes.
List I List II
(Products) (Casting Process) List I (Equipment) List II (Process)
A. Hollow statues 1. Centrifugal Casting
B. Dentures 2. Investment Casting P ‐ Hot Chamber Machine 1. Cleaning
C. Aluminium alloy pistons 3. Slush Casting Q ‐ Muller 2. Core making
D. Rocker arms 4. Shell Moulding R ‐ Dielectric Baker 3. Die casting
5. Gravity Die Casting
Codes: A B C D A B C D S ‐ Sand Blaster 4. Annealing
(a) 3 2 4 5 (b) 1 3 4 5 5. Sand mixing
(c) 1 2 3 4 (d) 3 2 5 4 (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
17
10/9/2011
IAS‐2004
Match 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 mixture
B. Electroslag casting 2. In this process, molten metal is forced by
Pressure into a metal mould
C. Centrifugal casting 3. This process employs a consumable electrode
D. Precision casting 4. This process involves rotating a mould while the
metal solidifies
5. This process produces very smooth, highly
Accurate castings from both ferrous and non
ferrous alloys
Codes:A B C D A B C D
(a) 5 4 1 2 (b) 2 3 4 5
(c) 5 3 4 2 (d) 2 4 1 5
Conventional Casting Process Ch‐21 Special Casting Process Ch‐22
Q. No Option Q. No Option
1A 13 C Q. No Option Q. No Option
1 D
2A 14 D 2 C 11 A
3 C 12 A
3C 15 D 4 B 13 D
5 C 14 A
4A 16 B 6 A 15 A
7 D 16 B
5D 17 B 8 C 17 A
9 B
6A 18 B 10 D
7D 19 D
8C 20 A
9B 21 A
10 D
11 A
12 B
18
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