1. INDUSTRIAL TRAINING REPORT
IN
PORWAL AUTO COMPONENTSLTD. PITHMPUR M.P.
IN
MAY-JUNE 2014
AMAN SHRIMAL
111101108
MATERIAL SCIENCE AND METALLURGICAL ENGINEERING
MAULANA AZAD NATIONAL INSTITUTE OF TECHNOLOGY,
BHOPAL (MP)

2. ACKNOWLEDGEMENT
I have taken efforts in this project. However, it would not have been possible without the kind
support and help of many individuals and organizations. I would like to extend my sincere thanks
to all of them.
I am highly indebted to Mr. Atin Jain, Mr. RK Sahu (HR), Mr. Sunil (Production in-charge) and
rest of the members of PORWAL AUTO COMPONENTS LTD. for their guidance and constant
supervision as well as for providing necessary information regarding the project & also for their
support in completing the project.
I would like to express my gratitude towards my parents and sister for their kind co-operation
and encouragement which help me in completion of this project.
I would like to express my special gratitude and thanks to industry persons for giving me such
attention and time.
My thanks and appreciations also go to my colleague in developing the project and people who
have willingly helped me out with their abilities.

3. CONTENTS
1. Company profile
2. Product manufactured
3. Facilities
4. Founding and casting
5. Foundry industry
5.1. Employment
5.2. Production
5.3. Investment
5.4. Raw material
5.5. Technology
6. Flow chart of process
7. Process
7.1. Mold making
7.2. Pattern making
7.3. Design
7.4. Material used
7.5. Sand casting
8. Melting
9. Cold box method
10. Sand
11. CO2 process
12. No bake
13. Mold material
14. Sand reclamation
15. Cast iron
15.1 Grey iron
15.2 Ductile iron
16. Leeb test
17. Brinell test
18. Vicker test
19. Sand test

4. Company Profile
Porwal Auto Components Ltd. (PACL) is involved in the manufacture of a variety of Ductile
Iron, Grey Cast Iron Steel and Steel Alloy Casting Components and Subassemblies. PACL caters
to the various sectors including Automobile, Engineering, Pumps and Valves, Agriculture and
Tractor Equipments, Construction Equipments, Machine Tools, Railways etc.
Porwal Auto Components Ltd. was incorporated in the year 1992 as an ancillary to M/s. Eicher
Motors Limited now VE Commercial Vehicles Ltd. (A Volvo Group and Eicher Motors joint
venture). PACL has registered impressive growth and has established itself as a trusted supplier
of Quality Castings and gained recognition from its customers for Outstanding Contribution to
Parts Development and Supply Chain Management.

5. Products being manufactured
1) Automotive parts
a) AXLE PARTS
i) DRUM BRAKE (FG-30)
ii) REAR WHEEL HUB (SG-500/7)
iii) BRAKE SHOE MACHINING (SG-400/12)
iv) FRONT WHEEL FLANGE (SG-500/7)
b) ENGINE PARTS
i) EXHAUST MANIFOLD (SG-400/12)
ii) EXHAUST BEND 4 Cyl.(SG-400/12)
iii) EXHAUST MANIFOLD 6 Cyl. (SG-400/12)
c) CHASSIS PARTS
i) BRACKET FOR AXEL ROD (SG-400/12)
ii) LEVER FOR ENGINE CONTROL( SG-400/12)
iii) FRONT SPRING REAR BKT( SG-400/12)
iv) LEVER ANCHOR (SG-500/7)
v) REAR SPRING BKT REAR ( SG-400/12)
vi) BRACKET ( SG-400/12)
vii) BELL CRANK LEVER ( SG-400/12)
viii) FRONT SPRING BKT FRONT( SG-400/12)
ix) BRACKET ( SG-400/12)
x) BRACKET FOR AXEL ROD ( SG-400/12)
xi) REAR SPRING MTG BKT FRONT ( SG-400/12)
xii) H SHACKLE FRONT( SG-400/12)
d) Transmission parts
i) HOUSING SPINDLE (SG450/10)
ii) COVER REAR (FC-25)
iii) NPUT COVER (FC-25)
iv) CASE TIMING GEAR (FC-25)
v) HOUSING G-1 (FC-25)
vi) CASE TRANSMISSION (FC-25)
e) Differential parts
i) DIFF CARRIER G ( SG-400/12 )
ii) THROUGH DRIVE HOUSING ( SG-400/12 )
iii) DIFF CASE . STRD. MTD.( SG-400/12 )
iv) FRONT WHEEL FLANGE ( SG-400/12 )
v) BEARING RETAINER (SG-500/7)
vi) DIFF CARRIER STRD. MTD. ( SG-400/12 )
2) Earthmoving
a) LINK LOADER (SG-500/7)
b) HOUSING (FC - 25)
c) BACK PLATE LUB. OIL PUMP (FC-25)
d) HOUSING 550 (FC - 25)
3) Locomotive
4) Heavy Engg. M/c parts
a) CASTING GEAR (FC-25)
b) HOUSING-450-(-FC-25-)

6. Facilities: Manufacturing
Casting
MELTING & CUPOLA
 1500 KW / 300 Hz VIP Dual track coreless Induction Furnace with 2 nos. 2000 Kg
Crucibles of Inductotherm Make.
 650 KW /500 Hz dual track core-less induction furnace with 1000 kg crucibles of
Inductotherm make.
POURING SYSTEM
 Pouring lines with bi-rail handling system.
 Pusher & pullers on track for handling mould box make Fonundarc.
MACHINE MOULDING
 Air Impulse High Pressure Molding Machine – FONDARC (French Design).
Rated Production Capacity 90 moulds per hour Box Size 700 X 700 X 300 / 300 mm
 2 Pairs DARPA -450 Molding Machines. Molding Box Size 500 X 500 X 175 / 250 mm,
650 X 600 X 175 / 250 mm
HEAVY MOULDING
 Dimension Maximum (In mm): 2000 x 2000 x 1000, Weight: 100 kg to 2000 kg
COLD BOX
 Fully automatic cold box sand preparation & distribution system. Capacity: 2 Ton/ Hrs.
Fully automatic residual gas scrubber for cold box Process. Capacity : 10000 CFM
 Fully Automatic Amine cold box machine with complete Hydraulic operation – 2 nos.
Parting: Vertical
Shot Capacity: 3 kg
Tooling Size: 400 X 250 X 250
Tooling Size: 500 X 250 X 300
 Fully Automatic Universal Amine cold box machine & operation Hydraulic.
Shot Capacity: 7.5 Kg
Parting: Vertical
Tooling Size: 500 X 250 X 300
 Fully Automatic Universal Amine cold box machine & operation Hydraulic.
Shot Capacity: 60Kg
Parting: Vertical: 700 X 400 X 500
Parting Horizontal: 700 X 500 X 500

7. SAND PLANT
SAND PLANT OF FONDARC MAKE (French Design) Capacity: 80 MT/ Hr with online sand
testing, online sand cooling & with fully automated, PLC controlled operations.
KNOCKOUT & DECORING
 Decoring cutter
 Tumbling barrel, make - jadav industry.
 Knock out 2000, make - sunny precision,
 Chipping hammer, make- Chicago pneumatic
FETTLING - FINISHING & PAINTING
 Cutter grinder, make- Chicago Pneumatic.
 Swing frame grinder.
 Pedestal grinder.
 Pneumatic hand grinder, Chicago Pneumatic.
 Pneumatic cutter, Chicago Pneumatic
 Heat treatment, make Dhan Prakash.
 Shot blasting m/c make Meera.
 Conveyorised hanger type shot blasting machines - 2Nos
 Conveyorized, forced air drying painting booth.
MATERIAL HANDLING
 E.O.T. crane f/c tapping 3 ton, make- Meeka Industries.
 Pouring hoist & ladle (1000kg & 500kg) make- Dhanprakash,
 Electric & power stacker, make- Godrej.
 Bundling machine, make-Sona Industries.
 Fork lift trucks make Godrej.
CORE SHOP
 Shell core shooter.
 Electric oven.
 Sand drier, make - Rhino Machinery.
 Core sand mixer make- J K Foundry.
PATTERN SHOP
 Methoding and simulation Through SOFTCAST. Pattern and Core Boxes are made on
CNC.
Maintenance of the tooling of the Tooling done in-house.
 Lathe machine, make-Kirlosker.
 Milling machine, make- Looper Engg.
 Drilling Machine.

8. TESTING
METALLURGICAL TESTING
 Microscope with Image Analyzer with magnification of 100 times
 Brinell hardness Tester
 Vickers hardness Tester
 Portable Leeb Hardness Tester
 Universal Testing Machine.
 Impact Testing machine ASTM.
CHEMICAL TESTING
 Spectrometer F20 Foundry Analyzer
 Metal Lab of GNR Italy for chemical composition
 C.E. apparatus with recorder
 Carbon Sulphur analyzer
 Other relevant wet analysis facilities
SAND TESTING
 Sieve Shaker
 Universal Sand Testing Machine
 Mould Hardness Tester
 Permeability Meter
 Moisture Tester.
METROLOGICAL TESTING
 Surface Finish Tester
 Slip Gauge
 Surface plate
 Conventional facilities for measurement.
 Inspection through CMM
NON DESTRUCTIVE TESTING
 Ultrasonic Flow Detector
 Dye Penetrant
 Magnetic flaw detector

9. Founding and Casting
The process of pouring molten metal into a cavity that has been molded according to a pattern of
the desired shape. When the metal solidifies, the result is a casting—a metal object conforming
to that shape. A great variety of metal objects are so molded at some point during their
manufacture.
The most common type of mold is made of sand and clay; ceramics, sand with cement, metals,
and other materials are also used for molds. These materials are packed over the face of the
pattern (usually made of wood, metal, or resin) that forms the cavity into which the molten metal
is to be poured. The pattern is removed from the mold when its shape is able to be retained by
the mold material. Molds are usually constructed in two halves, and the two halves are joined
together once the pattern has been removed from them. Pins and bushings permit precise joining
of the two halves, which together are enclosed in a mold box. The metal is then poured into the
mold through special gates and is distributed by runners to different areas of the casting. The
mold must be strong enough to resist the pressure of the molten metal and sufficiently permeable
to permit the escape of air and other gases from the mold cavity; otherwise, they would remain as
holes in the casting. The mold material must also resist fusion with the molten metal, and the
sand at the mold surface must be closely packed to give a smooth casting surface.
The making of patterns for foundries requires care and skill. Patterns are uniformly larger than
the desired casting in order to compensate for shrinkage during drops of temperature and the
liquid-to-solid phase change. Polystyrene foam patterns remain in the mold and evaporate upon
contact with the poured metal; wax patterns are melted out of the mold prior to the pouring of the
molten metal. Metal molds are used in that type of founding known as die-casting. Often a
hollow space is desired within the casting; in this case a core of fine sand is placed in one of the
mold halves. Core boxes made of wood, metal, or resin are also used in this regard.
Modern foundries capable of large-scale production are characterized by a high degree of
mechanization, automation, and robotics, and microprocessors allow for the accurate control of
automated systems. Advances in chemical binders have resulted in stronger molds and cores and
more accurate castings. Accuracy and purity are increased in vacuum conditions, and further
advances are expected from zero-gravity casting in space.
Foundry Industry
A foundry is a factory that produces metal castings. Metals are cast into shapes by melting them
into a liquid, pouring the metal in a mold, and removing the mold material or casting after the
metal has solidified as it cools. The most common metals processed are aluminium and cast iron.
However, other metals, such as bronze, brass, steel, magnesium, and zinc, are also used to
produce castings in foundries. In this process, parts of desired shapes and sizes can be formed.

10. According to the recent World Census of Castings by Modern Castings, USA India Ranks as 2nd
largest casting producer producing estimated 7.44 Million MT of various grades of Castings as
per international standards.
The various types of castings which are produced are ferrous, non ferrous, Aluminium Alloy,
graded cast iron, ductile iron, Steel etc. for application in Automobiles, Railways, Pumps
Compressors & Valves, Diesel Engines, Cement/Electrical/Textile Machinery, Aero & Sanitary
pipes & Fittings etc & Castings for special applications. However, Grey iron castings are the
major share approx 70 % of total castings produced.
There are approx 4500 units out of which 80% can be classified as Small Scale units & 10% each
as Medium & Large Scale units Approx 500 units are having International Quality Accreditation.
The large foundries are modern & globally competitive & are working at nearly full capacity.
Most foundries use cupolas using LAM Coke. There is growing awareness about environment &
many foundries are switching over to induction furnaces & some units in Agra are changing over
to coke less cupolas.
Employment
The industry directly employs about 5, 00,000 people & indirectly about 1, 50,000 people & is
labor intensive. The small units are mainly dependant on manual labor However, the medium &
large units are semi/ largely mechanized & some of the large units are world class.
Product-Mix
Grey iron is the major component of production followed by steel, ductile iron & non ferrous as
shown below.

11. Investments
India would need approx. $ 3 Billion in investment to meet the demand of growing domestic
industry and strong export drive. Following the economic reforms the Govt. of India has reduced
tariffs on imported capital goods as a result the annual average amount of FDI is reported to have
increased but is still one tenth of the annual FDI in China. The reforms also encourage the
privatization of industry enabling foreign companies to invest or enter into joint ventures with
Indian Foundries. FDI projects are permitted an automatic approval process. Several
International corporate from USA, EU and East Asian Countries have increased overseas
foundry operations in India. i.e. VOLVO foundries in Chennai and Suzuki in Haryana. Sundaram
Clayton has joined hands with Cummins. Hyundai Motors,
Delphi. Ford India, Tata-Cummins, GM and Ford have contracts of foundry products for export
with a value of $ 40 Million.

12. Raw material & Energy
Since 2003 the steep increase in cost of raw materials and energy have resulted in the closure of
approx. 500 units, Overall India is exporter of Pig Iron but must import Scrap metals and Coke
etc. Cost recovery for material and energy is very difficult as most contracts are long term
contracts without any clause for price adjustment. India has to import coke & scrap.Moulding
sand is locally available & India has an advantage on this account.
Energy cost typically vary between 12-15%
Labor
India has major competitive advantage over the foundry industries in the developed countries.
The total labor cost account for 12-15%
Technology
Govt. of India (GOI) has encouraged technology transfer through JV with foreign Companies
and GOI has cooperated with UNIDO with many foundry clusters. Indian foundry industry has
an edge over China for producing complex machined and precision castings as per international
quality standards. The GOI also helps upgrade foundry clusters. The clusters in Belgaum,
Coimbatore and Howrah are undergoing modernization under the industrial infrastructure up
gradation scheme. More of such clusters are likely to follow
The Institute of Indian Foundry men has plans to strengthen and develop various foundry
clusters.

13. Flow chart of the foundry processes:

14. Process
In metalworking, casting involves pouring liquid metal into a mold, which contains a hollow
cavity of the desired shape, and then allowing it to cool and solidify. The solidified part is also
known as a casting, which is ejected or broken out of the mold to complete the process. Casting
is most often used for making complex shapes that would be difficult or uneconomical to make
by other methods.
Mold making
In the casting process a pattern is made in the shape of the desired part. Simple designs can be
made in a single piece or solid pattern. More complex designs are made in two parts, called split
patterns. A split pattern has a top or upper section, called a cope, and a bottom or lower section
called a drag. Both solid and split patterns can have cores inserted to complete the final part
shape. Cores are used to create hollow areas in the mold that would otherwise be impossible to
achieve. Where the cope and drag separates is called the parting line.
When making a pattern it is best to taper the edges so that the pattern can be removed without
breaking the mold. This is called draft. The opposite of draft is an undercut where there is part of
the pattern under the mold material, making it impossible to remove the pattern without
damaging the mold.
The pattern is made out of wax, wood, plastic or metal. The molds are constructed by several
different processes dependent upon the type of foundry, metal to be poured, quantity of parts to
be produced, size of the casting and complexity of the casting. These mold processes include:
 Sand casting — Green or resin bonded sand mold.
 Lost-foam casting — Polystyrene pattern with a mixture of ceramic and sand mold.
 Investment casting — Wax or similar sacrificial pattern with a ceramic mold.
 Ceramic mold casting — Plaster mold.
 V-process casting — Vacuum is used in conjunction with thermoformed plastic to form sand
molds. No moisture, clay or resin is needed for sand to retain shape.
 Die casting — metal mold.
 Billet (ingot) casting — Simple mold for producing ingots of metal normally for use in other
foundries.

15. Patternmaking
The making of patterns, is a skilled trade that is related to the trades of tool and die
making and mold making, but also often incorporates elements of fine
woodworking. Patternmakers learn their skills through apprenticeships and trade schools over
many years of experience. Although an engineer may help to design the pattern, it is usually a
patternmaker who executes the design.
Design
Sprues, gates, risers, cores, and chills
The patternmaker or foundry engineer decides where the sprues, gating systems, and risers are
placed with respect to the pattern. Where a hole is desired in a casting, a core may be used which
defines a volume or location in a casting where metal will not flow into. Sometimes chills may
be placed on a pattern surface prior to molding, which are then formed into the sand mould.
Chills are heat sinks which enable localized rapid cooling. The rapid cooling may be desired to
refine the grain structure or determine the freezing sequence of the molten metal which is poured
into the mould. Because they are at a much cooler temperature, and often a different metal than
what is being poured, they do not attach to the casting when the casting cools. The chills can then
be reclaimed and reused.
The design of the feeding and gating system is usually referred to as methoding or methods
design. It can be carried out manually, or interactively using general-purpose CAD software, or
semi-automatically using special-purpose software (such as Auto CAST).
Types of Patterns
 Single piece pattern
 Multi-piece pattern
 Gated pattern
 Sweep pattern
 Skeleton pattern
 Shell pattern
 Loose piece pattern
Allowances
To compensate for any dimensional and structural changes which will happen during the casting
or patterning process, allowances are usually made in the pattern.
Contraction allowances / Shrinkage allowance
The pattern needs to incorporate suitable allowances for shrinkage; these are called contraction
allowances, and their exact values depend on the alloy being cast and the exact sand casting
method being used. Some alloys will have overall linear shrinkage of up to 2.5%, whereas other

16. alloys may actually experience no shrinkage or a slight "positive" shrinkage or increase in size in
the casting process (notably type metal and certain cast irons). The shrinkage amount is also
dependent on the sand casting process employed, for example clay-bonded sand, chemical
bonded sands, or other bonding materials used within the sand. This was traditionally accounted
for using a shrink rule, which is an oversized rule.
Shrinkage can again be classified into Liquid shrinkage and solid shrinkage. Liquid shrinkage is
the reduction in volume during the process of solidification, and Solid shrinkage is the reduction
in volume during the cooling of the cast metal.
Generally during shrinkage, all dimensions are going to be altered uniformly, unless there is a
restriction.
Draft allowance
When the pattern is to be removed from the sand mold, there is a possibility that any leading
edges may break off, or get damaged in the process. To avoid this, a taper is provided on the
pattern, so as to facilitate easy removal of the pattern from the mold, and hence reduce damage to
edges. The taper angle provided is called the Draft angle. The value of the draft angle depends
upon the complexity of the pattern, the type of molding (hand molding or machine molding),
height of the surface, etc. Draft provided on the casting 1 to 3 degrees on external surface (5 to 8
internal castings).
Finishing or machining allowance
The surface finish obtained in sand castings is generally poor (dimensionally inaccurate), and
hence in many cases, the cast product is subjected to machining processes like turning
or grinding in order to improve the surface finish. During machining processes, some metal is
removed from the piece. To compensate for this, a machining allowance (additional material)
should be given in the casting.
Shake allowance
Usually during removal of the pattern from the mold cavity, the pattern is rapped all around the
faces, in order to facilitate easy removal. In this process, the final cavity is enlarged. To
compensate for this, the pattern dimensions need to be reduced. There are no standard values for
this allowance, as it is heavily dependent on the personnel. This allowance is a negative
allowance, and a common way of going around this allowance is to increase the draft allowance.
Shaking of pattern causes enlargement of mould cavity and results in a bigger casting.
Distortion allowance

17. During cooling of the mold, stresses developed in the solid metal may induce distortions in the
cast. This is more evident when the mold is thinner in width as compared to its length. This can
be eliminated by initially distorting the pattern in the opposite direction.
Demand
Patterns continue to be needed for sand casting of metals. For the production of gray iron, ductile
iron and steel castings, sand casting remains the most widely used process. For aluminum
castings, sand casting represents about 12% of the total tonnage by weight (surpassed only by die
casting at 57%, and semi-permanent and permanent mold at 19%; based on 2006 shipments).
The exact process and pattern equipment is always determined by the order quantities and the
casting design. Sand casting can produce as little as one part, or as many as a million copies.
Materials used
Typically, materials used for pattern making are wood, metal or plastics.
Wax and Plaster of Paris are also used, but only for specialized applications.
Mahogany is the most commonly used material for patterns, primarily because it is soft, light,
and easy to work. The downside is that it wears out fast, and is prone to moisture attack.
Metal patterns are more long lasting, and do not succumb to moisture, but they are heavier and
difficult to repair once damaged.
Wax patterns are used in a casting process called investment casting. A combination of paraffin
wax, bees wax and carnauba wax is used for this purpose.
Plaster of Paris is usually used in making master dies and molds, as it gains hardness quickly,
with a lot of flexibility when in the setting stage.
Sand casting
Sand casting, also known as sand molded casting, is a metal casting process characterized by
using sand as the mold material. The term "sand casting" can also refer to an object produced via
the sand casting process. Sand castings are produced in specialized factories called foundries.
Over 70% of all metal castings are produced via a sand casting process.
Sand casting is relatively cheap and sufficiently refractory even for steel foundry use. In
addition to the sand, a suitable bonding agent (usually clay) is mixed or occurs with the sand.
The mixture is moistened, typically with water, but sometimes with other substances, to develop
strength and plasticity of the clay and to make the aggregate suitable for molding. The sand is
typically contained in a system of frames or mold boxes known as a flask. The mold
cavities and gate system are created by compacting the sand around models, or patterns, or
carved directly into the sand.

18. Basic process
There are six steps in this process:
1. Place a pattern in sand to create a mold.
2. Incorporate the pattern and sand in a gating system.
3. Remove the pattern.
4. Fill the mold cavity with molten metal.
5. Allow the metal to cool.
6. Break away the sand mold and remove the casting.
Molding box and materials
A multi-part molding box (known as a casting flask, the top and bottom halves of which are
known respectively as the cope and drag) is prepared to receive the pattern. Molding boxes are
made in segments that may be latched to each other and to end closures. For a simple object—
flat on one side—the lower portion of the box, closed at the bottom, will be filled with molding
sand. The sand is packed in through a vibratory process called ramming, and in this case,
periodically screened level. The surface of the sand may then be stabilized with a sizing
compound. The pattern is placed on the sand and another molding box segment is added.
Additional sand is rammed over and around the pattern. Finally a cover is placed on the box and
it is turned and unlatched, so that the halves of the mold may be parted and the pattern with its
sprue and vent patterns removed. Additional sizing may be added and any defects introduced by
the removal of the pattern are corrected. The box is closed again. This forms a "green" mold
which must be dried to receive the hot metal. If the mold is not sufficiently dried a steam
explosion can occur that can throw molten metal about. In some cases, the sand may be oiled
instead of moistened, which makes possible casting without waiting for the sand to dry. Sand
may also be bonded by chemical binders, such as furane resins or amine-hardened resins.
Chills
To control the solidification structure of the metal, it is possible to place metal plates, chills, in
the mold. The associated rapid local cooling will form a finer-grained structure and may form a
somewhat harder metal at these locations. In ferrous castings, the effect is similar
to quenching metals in forge work. The inner diameter of an engine cylinder is made hard by a
chilling core. In other metals, chills may be used to promote directional solidification of the
casting. In controlling the way a casting freezes, it is possible to prevent internal voids or
porosity inside castings.
Cores
To produce cavities within the casting—such as for liquid cooling in engine blocks and cylinder
heads—negative forms are used to produce cores. Usually sand-molded, cores are inserted into
the casting box after removal of the pattern. Whenever possible, designs are made that avoid the
use of cores, due to the additional set-up time and thus greater cost.
With a completed mold at the appropriate moisture content, the box containing the sand mold is
then positioned for filling with molten metal—
typically iron, steel, bronze, brass, aluminium, magnesium alloys, or various pot metal alloys,

19. which often include lead, tin, and zinc. After filling with liquid metal the box is set aside until
the metal is sufficiently cool to be strong. The sand is then removed revealing a rough casting
that, in the case of iron or steel, may still be glowing red. When casting with metals like iron or
lead, which are significantly heavier than the casting sand, the casting flask is often covered with
a heavy plate to prevent a problem known as floating the mold. Floating the mold occurs when
the pressure of the metal pushes the sand above the mold cavity out of shape, causing the casting
to fail.
After casting, the cores are broken up by rods or shot and removed from the casting. The metal
from the sprue and risers is cut from the rough casting. Various heat treatments may be applied
to relieve stresses from the initial cooling and to add hardness—in the case of steel or iron, by
quenching in water or oil. The casting may be further strengthened by surface compression
treatment—like shot peening—that adds resistance to tensile cracking and smoothes the rough
surface.
Design requirements
The part to be made and its pattern must be designed to accommodate each stage of the process,
as it must be possible to remove the pattern without disturbing the molding sand and to have
proper locations to receive and position the cores. A slight taper, known as draft, must be used on
surfaces perpendicular to the parting line, in order to be able to remove the pattern from the
mold. This requirement also applies to cores, as they must be removed from the core box in
which they are formed. The sprue and risers must be arranged to allow a proper flow of metal
and gasses within the mold in order to avoid an incomplete casting. Should a piece of core or
mold become dislodged it may be embedded in the final casting, forming sand pit, which may
render the casting unusable. Gas pockets can cause internal voids. These may be immediately
visible or may only be revealed after extensive machining has been performed. For critical
applications, or where the cost of wasted effort is a factor, non-destructive testing methods may
be applied before further work is performed.
Mechanized sand molding
The mechanized molding lines consisted of sand slingers and/or jolt-squeeze devices that
compacted the sand in the flasks. Subsequent mold handling was mechanical using cranes, hoists
and straps. After core setting the copes and drags were coupled using guide pins and clamped for
closer accuracy. The molds were manually pushed off on a roller conveyor for casting and
cooling.
Automatic high pressure sand molding lines
Increasing quality requirements made it necessary to increase the mold stability by applying
steadily higher squeeze pressure and modern compaction methods for the sand in the flasks. In
early fifties the high pressure molding was developed and applied in mechanical and later
automatic flask lines. The first lines were using jolting and vibrations to pre-compact the sand in
the flasks and compressed air powered pistons to compact the molds.
Horizontal sand flask molding
In the first automatic horizontal flask lines the sand was shot or slung down on the pattern in a
flask and squeezed with hydraulic pressure of up to 140 bars. The subsequent mold handling
including turn-over, assembling, pushing-out on a conveyor was accomplished either manually
or automatically. In the late fifties hydraulically powered pistons or multi-piston systems were

20. used for the sand compaction in the flasks. This method produced much more stable and accurate
molds than it was possible manually or pneumatically. In the late sixties mold compaction by fast
air pressure or gas pressure drop over the pre-compacted sand mold was developed (sand-
impulse and gas-impact).
The major disadvantages of these systems is high spare parts consumption due to multitude of
movable parts, need of storing, transporting and maintaining the flasks and productivity limited
to approximately 90–120 molds per hour.
Vertical sand flask-less molding
A flask-less molding process by using vertically parted and poured molds. The first line could
produce up to 240 complete sand molds per hour. Molding lines can achieve a molding rate of
550 sand molds per hour and requires only one monitoring operator. Maximum mismatch of two
mold halves is 0.1 mm (0.0039 in). Although very fast, vertically parted molds are not typically
used by jobbing foundries due to the specialized tooling needed to run on these machines. Cores
need to be set with a core mask as opposed to by hand and must hang in the mold as opposed to
being set on parting surface.
Match-plate sand molding
The principle of the matchplate, meaning pattern plates with two patterns on each side of the
same plate, was developed and patented in 1910, fostering the perspectives for future sand
molding improvements. However, first in the early sixties the American company Hunter
Automated Machinery Corporation launched its first automatic flaskless, horizontal molding line
applying the matchplate technology.
The matchplate molding technology is today used widely. Its great advantage is inexpensive
pattern tooling, easiness of changing the molding tooling, thus suitability for manufacturing
castings in short series so typical for the jobbing foundries. Modern matchplate molding machine
is capable of high molding quality, less casting shift due to machine-mold mismatch (in some
cases less than 0.15 mm (0.0059 in)), consistently stable molds for less grinding and improved
parting line definition. In addition, the machines are enclosed for a cleaner, quieter working
environment with reduced operator exposure to safety risks or service-related problems.

21. Melting
Melting metal in a crucible for casting
Melting is performed in a furnace. Virgin material, external scrap, internal scrap, and alloying
elements are used to charge the furnace. Virgin material refers to commercially pure forms of the
primary metal used to form a particular alloy. Alloying elements are either pure forms of an
alloying element, like electrolytic nickel, or alloys of limited composition, such as ferroalloys or
master alloys. External scrap is material from other forming processes such as punching, forging,
or machining. Internal scrap consists of gates, risers, defective castings, and other extraneous
metal oddments produced within the facility.
The process includes melting the charge, refining the melt, adjusting the melt chemistry and
tapping into a transport vessel. Refining is done to remove deleterious gases and elements from
the molten metal to avoid casting defects. Material is added during the melting process to bring
the final chemistry within a specific range specified by industry and/or internal standards.
Certain fluxes may be used to separate the metal from slag and/or dross and degassers are used to
remove dissolved gas from metals that readily dissolve certain gasses. During the tap, final
chemistry adjustments are made.
Furnace
Furnaces are refractory lined vessels that contain the material to be melted and provide the
energy to melt it. Modern furnace types include electric arc furnaces (EAF), induction
furnaces, cupolas, reverberatory, and crucible furnaces. Furnace choice is dependent on the alloy
system quantities produced. For ferrous materials EAFs, cupolas, and induction furnaces are

22. commonly used. Reverberatory and crucible furnaces are common for producing aluminium,
bronze, and brass castings.
The design can be optimized based on multiple factors. Furnaces in foundries can be any size,
ranging from small ones used to melt precious metals to furnaces weighing several tons,
designed to melt hundreds of pounds of scrap at one time. They are designed according to the
type of metals that are to be melted. Furnaces must also be designed based on the fuel being used
to produce the desired temperature. For low temperature melting point alloys, such as zinc or tin,
melting furnaces may reach around 500° C. Electricity, propane, or natural gas is usually used to
achieve these temperatures. For high melting point alloys such as steel or nickel based alloys, the
furnace must be designed for temperatures over 1600° C. The fuel used to reach these high
temperatures can be electricity (as employed in electric arc furnaces) or coke.
The majority of foundries specializes in a particular metal and has furnaces dedicated to these
metals. For example, an iron foundry (for cast iron) may use a cupola, induction furnace, or
EAF, while a steel foundry will use an EAF or induction furnace. Bronze or brass foundries use
crucible furnaces or induction furnaces. Most aluminium foundries use either electric resistance
or gas heated crucible furnaces or reverberatory furnaces.
Melting furnaces used in the foundry industry are of diverse configurations. The selection of the
melting unit is one of the most important decisions foundries must make with due consideration
to several important factors including:
1. The temperature required to melt the alloy
2. The melting rate and quantity of molten metal required
3. The economy of installation and operation
4. Environmental and waste disposal requirements
Induction Furnaces
The principle of induction melting is that a high voltage electrical source from a primary coil
induces a low voltage, high current in the metal or secondary coil. Induction heating is simply a
method of transferring heat energy.
Induction furnaces are ideal for melting and alloying a wide variety of metals with minimum
melt losses, however, little refining of the metal is possible. There are two main types of
induction furnace: coreless and channel.
The heart of the coreless induction furnace is the coil, which consists of a hollow section of
heavy duty, high conductivity copper tubing which is wound into a helical coil. Coil shape is
contained within a steel shell and magnetic shielding is used to prevent heating of the supporting
shell. To protect it from overheating, the coil is water-cooled, the water being re-circulated and

23. cooled in a cooling tower. The shell is supported on trunnions on which the furnace tills to
facilitate pouring.
The crucible is formed by ramming a granular refractory between the coil and a hollow internal
former which is melted away with the first heat leaving a sintered lining.
The power cubicle converts the voltage and frequency of main supply, to that required for
electrical melting. Frequencies used in induction melting vary from 50 cycles per second (mains
frequency) to 10,000 cycles per second (high frequency). The higher the operating frequency, the
greater the maximum amount of power that can be applied to a furnace of given capacity and the
lower the amount of turbulence induced.
When the charge material is molten, the interaction of the magnetic field and the electrical
currents flowing in the induction coil produce a stirring action within the molten metal. This
stirring action forces the molten metal to rise upwards in the centre causing the characteristic
meniscus on the surface of the metal. The degree of stirring action is influenced by the power
and frequency applied as well as the size and shape of the coil and the density and viscosity of
the molten metal. The stirring action within the bath is important as it helps with mixing of alloys
and melting of turnings as well as homogenizing of temperature throughout the furnace.
Excessive stirring can increase gas pick up, lining wear and oxidation of alloys.
In all coreless induction furnaces, there is an “ideal” refractory wall thickness, carefully
calculated by the manufacturers to offer the optimum melting performance. Designed into this
calculation are
1. Safety considerations
2. Electrical characteristics of the coil
3. Metallic charge electrical conductivity
4. Structural and refractory considerations
5. Operational constraints
6. Production needs.
When the furnace melt diameter is reduced by buildup, the melting process becomes
compromised. Traditionally, to remove the buildup, furnace operators must mechanically scrape
the lining that may also damage the refractory face. During this process, the power is generally
reduced for safety reasons. The result is a reduction in the percent power utilization that causes
the energy consumption to increase, which is graphically shown below:
.

24. Furnace operators often scrape slag buildup from the lining, which may damage the
refractory face. During this process, power is generally reduced for safety
considerations. The result is a reduction in thepercent power utilization that causes
the energy consumption to increase.
Slag formation is inevitable during melting. In a coreless induction furnace, slag residuals
normally deposit along the refractory walls and within the active power coil. The composition of
slag varies with the type of metal being melted in a coreless furnace. The cleanliness of the
metallic charge, (consisting of sand-encrusted gates and risers, or rust- and dirt-encrusted scrap)
significantly affects the type of slag formed during the melting operation. Because these oxides
and non-metallic’s are not soluble in the molten metal, they float in the liquid metal as an
emulsion. This emulsion of slag particles remains stable if the molten metal is continuously
agitated, the result of the magnetic stirring inherent in coreless induction melting. Until the
particle size of the nonmetallic increases to the point where buoyancy effects countervail the
stirring action, the particle will remain suspended. When flotation effects become great enough,
non-metallic’s rise to the surface of the molten metal and agglomerate as slag. Once the
nonmetallics coalesce into a floating mass on the liquid metal they can be removed. The use of
fluxes accelerates these processes.

25. Fluxes will help to maintain slags at a melting point below the coldest temperature
in the system; to prevent slags and other insolubles from freezing on cooler
refractory surfaces; to encourage flotation of the emulsified oxides; and to reduce
the melting point of the slag below the lowest temperature in the furnace and liquid
metal handling system.
When slag makes contact with the hot face of the refractory wall that is colder than the melting
point of the slag, the cooling slag will adhere to the lining. This adhering material is called
buildup. High-melting point slags are especially prone to promoting buildup. If not prevented
from forming or not removed as it forms, buildup will reduce the overall efficiency.
Controlling buildup allows for continuous furnace operation. Buildup can be controlled or
eliminated with the addition of fluxes. It should be noted that in the past ferrous foundries have
been discouraged from using fluxes by refractory companies. However, new developments in
flux chemistry (Redux U.S. Patent 7, 68,473) allow fluxes to be used in furnaces lined with even
silica refractory, without refractory attack. Generally, adding fluxes ensures that slags have a
melting point below the coldest temperature in the system. Fluxes can help prevent slags and
other insolubles from freezing on the cooler refractory surfaces. Using a flux allows for the
flotation of the emulsified oxides; it also reduces the melting point of the slag to below the
lowest temperature encountered in the melting furnace and associated liquid metal handling
system.

26. Improper use of fluxes can rapidly erode refractory furnace linings, especially if potent fluorspar-
based fluxes are used. However, if a flux is carefully engineered for specific applications and
used properly, refractory life may actually increase. Some foundries using specialty fluxes have
reported increased refractory life. One large foundry significantly increased lining life from 11
months to 26 months just by incorporating Redux in their operation. Refractory life also can be
extended by reduced damage due to mechanical chipping required to remove tenacious slag
deposits. Elimination of buildup optimizes power utilization, thereby reducing energy
consumption.
Foundry G is a medium-sized manufacturer of gray iron castings. It has historically experienced
extensive slag buildup on the upper sidewalls of its four 3-ton medium-frequency coreless
induction furnaces in a semi-batch melting operation. Foundry G’s charge consists of 100%
metallic fines. Each coreless furnace is lined with a silica dry vibratable refractory. During
melting, slag generation and accompanying buildup immediately reduced furnace capacity and
contributed to increased power consumption. After 48 hours of operation, three inches of buildup
occurred along the entire sidewall. Foundry G initially incorporated 2 lb of Redux EF40L flux
per ton of charge, added to each back-charge to determine its effect on buildup. EF40L was
placed in the furnace before back charging on top of existing molten metal to ensure excellent
mixing (a minimum 50% molten metal bath). Immediate improvements were observed and
buildup along the sidewalls was essentially eliminated. Foundry G observed the following
benefits by using Redux on a continuous basis:
1. Using Redux EF40 reduced “bridging” tendencies due to cleaner refractory walls
2. Reduced power consumption during each melt
3. Hourly maintenance from scraping was greatly reduced
4. Consistent furnace capacities, with less interruption for charging delays
5. Improved “electrical coupling” was observed with improved temperature control
6. No adverse effects on the dry vibratable silica refractory linings.
Foundry D operates two, 12-metric ton, 9,000-kW, 180-Hz medium frequency coreless furnaces
batch melting ductile-base iron. Each 12-metric ton charge consists of 15% ductile pig iron,
followed by the addition of 35% carbon steel clips and 50% ductile returns. Tap temperatures
average 2,775°F. Current batch melt time (from charging to completely molten) is typically 40-
50 minutes per heat. The furnace is lined with a dry-vibratable silica lining. Without fluxing,
buildup would occur along the sidewalls of the furnace, including in the active power coil. This
caused delays in charging, reduced furnace capacity, and longer downtime for scraping the
lining, adding an additional 5 to 15 minutes per heat. Buildup above the molten metal line (top
cap area) caused additional production delays. By adding 6 lbs of Redux EF40 flux with each
charge, slag buildup is eliminated. Refractory lining life increased from 4,500 tons throughput to
7,500 tons per lining installation. Foundry D continues to realize the following benefits from
fluxing:

27. 1. Furnace volume remains constant at 12 metric tons
2. Consistent melting cycles of 40-50 minutes for each charge
3. Less frequent top cap cleaning
4. Delays at the mold line for molten iron was reduced by 50%
5. Reduced mechanical damage to the refractory by eliminating scraping.
Insoluble buildup and slag related problems have become serious issues for foundries. These
problems will likely increase as the quality of scrap continues to deteriorate. Using fluxes
properly can alleviate these challenges while increasing melting efficiency and saving foundries
time and electricity, and most important, improving profitability.
Heat recovery can provide significant energy and cost savings as well as environmental benefits.
Today, as energy costs escalate, heat recovery efforts may lead to an attractive payback and help
many foundries reduce their carbon footprints, as well as contribute to a more sustainable
society.
To remove the heat generated by the induction coil, as well as the thermal loss from the
refractory system in the induction furnace, water cooling is commonly used. This heated fluid is
typically pumped to an exterior mounted cooling tower. In the induction melt shop, the high
efficiency power supply powering the furnace typically has a low water temperature rise on the
electrical/ electronic components. Thus, heat recovery for the power supply system is typically
not economical. However, in some cases, this temperature rise is fed to a water-to-water heat
exchanger feeding the furnace and raising the inlet temperature, thus enhancing overall recovery.
While almost all the heat is produced in the melting furnace and, in most cases under full power,
an expected 40°F+ temperature rise is common. This temperature level is lower than the drain
temperature sensor range/furnace safety cutout. Typical furnace drain water runs in the 140°F
temperature range. Some applications may be in the 150°F range or higher, based on the
application and type of system.
While today’s furnaces offer high electrical efficiency, a sizable amount (20-30%) of the rated
power can be recovered from the furnace coil water temperature generated by the I2R losses
(current on the coil), as well as thermal refractory loss in the furnace. To recover the heat in the
cooling water based on geographical location, a number of options exist. Each location, as well
as the cooling system type, must be considered for a cost-effective air handler and cooling
system selection.
A heat recovery system should always be

28. considered as a secondary selection after choosing the highest efficiency melt system that offers
the lowest energy consumption per ton of melted metal.
As noted, today’s melt shops need to look at the long term and always keep in mind the “life
cycle cost,” supplementing cost reductions with secondary selections, such as heat recovery, zero
discharge water cooling systems, charging systems or, the most recent addition, the Automated
Robotic Melt Shop System. All secondary selections carry a relatively small cost added up front
with sizable benefits realized during the years of operation.
Metal and pouring sections of the foundry should be provided with hard hats, tinted eye
protection and face shields, aluminized clothing such as aprons, gaiters or spats (lower-leg and
foot coverings) and boots. Use of protective equipment should be mandatory, and there should be
adequate instruction in its use and maintenance. High standards of housekeeping and exclusion
of water to the highest degree possible are needed in all areas where molten metal is being
manipulated.
Where large ladles are slung from cranes or overhead conveyors, positive ladle-control devices
should be employed to ensure that spillage of metal cannot occur if the operator releases his or
her hold. Hooks holding molten metal ladles must be periodically tested for metal fatigue to
prevent failure.
The pouring station is provided with a compensating hood with a direct air supply. The poured
mould proceeds along the conveyor through an exhausted cooling tunnel until shakeout. In case
moulds may be poured on a foundry floor and allowed to burn off there. In this situation, the
ladle should be equipped with a mobile exhaust hood.
Tapping and transport of molten iron and charging of electric furnaces creates exposure to iron
oxide and other metal oxide fumes. Pouring into the mould ignites and pyrolyses organic
materials, generating large amounts of carbon monoxide, smoke, carcinogenic polynuclear
aromatic hydrocarbons (PAHs) and pyrolysis products from core materials which may be
carcinogenic and also respiratory sensitizers. Moulds containing large polyurethane bound cold
box cores release a dense, irritating smoke containing isocyanates and amines. The primary
hazard control for mould burn off is a locally exhausted pouring station and cooling tunnel.
In foundries with roof fans for exhausting pouring operations, high metal fume concentrations
may be found in the upper regions where crane cabs are located. If the cabs have an operator, the
cabs should be enclosed and provided with filtered, conditioned air.

29. Cold box
Use organic and inorganic binders that strengthen the mold by chemically adhering to the sand.
This type of mold gets its name from not being baked in an oven like other sand mold types. This
type of mold is more accurate dimensionally than green-sand molds but is more expensive. Thus
it is used only in applications that necessitate it.
Cold Box Process As the name already indicates, the cold box process is based on the reaction
of two components with polyurethane. A poly addition of the part 1 component, the phenol-
formaldehyde resin, and the part 2 components, the isocyanate, is initiated through basic
catalysis, usually by means of gassing with a tertiary amine.
The hardening reaction is very fast, which makes the cold box process attractive for the highly
productive production of series components in particular. The high strength level enables fast
and automated core production with process reliability. The cores can be cast just a short time
after production and feature high thermal stability, which also allows the dimensionally accurate
production of water jackets or oil duct cores. Due to their almost pH-neutral properties, high
proportions of mechanically or thermally treated used sands from cold box production can be
reused.
Properties and advantages
 Rapid model change possible (cold core boxes)
 Excellent thermal stability
 Short cycle times and high productivity thanks to rapid hardening
 Secure core extraction, low core fracture thanks to high initial strength
 High dimensional accuracy
 Smooth core surfaces
 Low tooling and energy costs
The main reason why the cold box process is so successful is that it makes it possible to achieve
complicated core geometries with high dimensional accuracy and high productivity. When
looking at the overall process of core production, the cold box process is distinguished by the
fact that the cores that were shot can be mounted to core packages and coated directly after
production, i.e. short cycle times are possible from the shot to the core that is ready to use.
Excellent disintegration after casting and various possibilities of regeneration with very high
reuse rates round off the picture.

30. Fundamentals of the process, the components, phenol-formaldehyde resin and isocyanate, are
mixed with the mold material, compressed in a core box and hardened with a catalyst. The
addition rates can vary depending on the application and mold material; in relation to the mold
material, they are usually between 0.4% and 1.2% per part. The binder bridges that develop
during the reaction (see SEM photo) ensure that the molding material compound is stable. After
casting, the casting heat has weakened the binder bridges to the extent that the sand can be
removed from the cast part by means of mechanical input.
SEM photo of binder bridges
Advantage:
Economic and automatic core production and excellent possibilities for “online production.” The
cores are inserted into the ingot or green sand mold as soon as possible after production and then
cast.
Requirements for cold box
The most important prerequisite for standing one’s ground in the international competition is to
produce high quality cast parts with intricate geometry at a reasonable price. The most important
market requirements for the cold box resin are:
 High reactivity
 Reduced emission and odor pollution or a low concentration of monomers (free phenol
and free formaldehyde)
 Reduction of amine consumption
 Long processing time (bench life) of the sand mixture
 High core box cleanliness
 High strength level
 High thermal resistance (thermal stability)
 High stability with respect to water-based coatings (hydro-stability)

31. In general, we can distinguish between two methods of sand casting; the first one using green
sand and the second being the air set method.
Green sand
These expendable molds are made of wet sands that are used to make the mold's shape. The
name comes from the fact that wet sands are used in the molding process. Green sand is not
green in color, but "green" in the sense that it is used in a wet state (akin to green wood). Unlike
the name suggests, "Green sand" is not a type of sand on its own, but is rather a mixture of:
 Silica sand (SiO2), or chromite sand (FeCr2O), or zircon sand (ZrSiO4), 75 to 85%,
or olivine, or staurolite, or graphite.
 bentonite (clay), 5 to 11%
 water, 2 to 4%
 inert sludge 3 to 5%
 Anthracite (0 to 1%)
There are many recipes for the proportion of clay, but they all strike different balances between
mold ability, surface finish, and ability of the hot molten metal to degas. The coal typically
referred to in foundries as sea-coal, which is present at a ratio of less than 5%, partially combusts
in the presence of the molten metal leading to off gassing of organic vapors. Green Sand for non-
ferrous metals do not use coal additives since the CO created is not effective to prevent
oxidation. Green Sand for aluminum typically uses olivine sand (a mixture of the
minerals forsterite and fayalite which are made by crushing dunite rock). The choice of sand has
a lot to do with the temperature that the metal is poured. At the temperatures that copper and iron
are poured, the clay gets inactivated by the heat in that the montmorillonite is converted to illite,
which is non-expanding clay. Most foundries do not have the very expensive equipment to
remove the burned out clay and substitute new clay; so instead, those that pour iron typically
work with silica sand that is inexpensive compared to the other sands. As the clay is burned out,
newly mixed sand is added and some of the old sand is discarded or recycled into other uses.
Silica is the least desirable of the sands since metamorphic grains of silica sand have a tendency
to explode to form sub-micron sized particles when thermally shocked during pouring of the
molds. These particles enter the air of the work area and can lead to silicosis in the workers. Iron
foundries spend a considerable effort on aggressive dust collection to capture this fine silica. The
sand also has the dimensional instability associated with the conversion of quartz from alpha
quartz to beta quartz at 1250 degrees F. Often additives such as wood flour are added to create a
space for the grains to expand without deforming the mold. Olivine, Chromites, etc. are used
because they do not have a phase conversion that causes rapid expansion of the grains, as well as
offering greater density, which cools the metal faster and produces finer grain structures in the
metal. Since they are not metamorphic, they do not have the polycrystals found in silica, and
subsequently do not form hazardous sub-micron sized particles.
The "air set" method
The air set method uses dry sand bonded with materials other than clay, using a fast
curing adhesive. The latter may also be referred to as no bake mold casting. When these are used,
they are collectively called "air set" sand castings to distinguish them from "green sand" castings.
Two types of molding sand are natural bonded (bank sand) and synthetic (lake sand); the latter is
generally preferred due to its more consistent composition.

32. With both methods, the sand mixture is packed around a pattern, forming a mold cavity. If
necessary, a temporary plug is placed in the sand and touching the pattern in order to later form a
channel into which the casting fluid can be poured. Air-set molds are often formed with the help
of a casting flask having a top and bottom part, termed the cope and drag. The sand mixture is
tamped down as it is added around the pattern, and the final mold assembly is sometimes
vibrated to compact the sand and fill any unwanted voids in the mold. Then the pattern is
removed along with the channel plug, leaving the mold cavity. The casting liquid (typically
molten metal) is then poured into the mold cavity. After the metal has solidified and cooled, the
casting is separated from the sand mold. There is typically no mold release agent, and the mold is
generally destroyed in the removal process.
The accuracy of the casting is limited by the type of sand and the molding process. Sand
castings made from coarse green sand impart a rough texture to the surface, and this makes them
easy to identify. Castings made from fine green sand can shine as cast but are limited by the
depth to width ratio of pockets in the pattern. Air-set molds can produce castings with smoother
surfaces than coarse green sand but this method is primarily chosen when deep narrow pockets in
the pattern are necessary, due to the expense of the plastic used in the process. Air-set castings
can typically be easily identified by the burnt color on the surface. The castings are typically shot
blasted to remove that burnt color. Surfaces can also be later ground and polished, for example
when making a large bell. After molding, the casting is covered with a residue of oxides, silicates
and other compounds. This residue can be removed by various means, such as grinding, or shot
blasting.
During casting, some of the components of the sand mixture are lost in the thermal casting
process. Green sand can be reused after adjusting its composition to replenish the lost moisture
and additives. The pattern itself can be reused indefinitely to produce new sand molds. The sand
molding process has been used for many centuries to produce castings manually. Since 1950,
partially automated casting processes have been developed for production lines.
Sodium Silicate/CO2Coremaking
One of the easiest modern core making processes for instructional and small foundries to use is
the sodium silicate/ CO2process. In this process, liquid sodium silicate is mixed with the sand.
The sand is rammed into a core box and cured by passing CO2 through the core. Sodium silicate
cores are very strong. The bond is so strong that hot tearing and collapsibility can be an issue.
Cores made from this process produce less gas than other processes. Cleanup is also easy since
water can dissolve the sodium silicate. The environmental friendliness, ease of cleanup, and
simplicity makes the process very simple to conduct in the teaching foundry.
The sodium silicate/CO2process hardens through the following reaction:
Na2Si2O5.H2O (l) +CO2 (g) = SiO2 (gel) +Na2CO3.H2O (glass)
The silica gel that is formed binds individual sand grains together. Sand temperature is critical in
this process. The core should be between 25ºC to 30ºC (75ºF to 85ºF). Below 15ºC (60ºF) the
reaction proceeds very slowly, and more CO2 or gassing time is required to fully cure the core.
Above 30ºC, excessive amounts of moisture evaporate during the curing process, resulting in a

33. very weak and brittle bond. It should also be noted that the gel tends to hydrate, which causes a
reduction in binder strength. This limits core shelf life to about one month. Experience at SVSU
has found shelf life can be as long as two months during winter.
There are several things to keep in mind when developing a recipe for cores. Most liquid sodium
silicate has a ratio of 3.22 parts silica to one part sodium oxide. This material is not suitable for
foundry core making. A ratio of 2.4 to 2.6 is appropriate for cores. Schools should contact one of
the many foundry industry suppliers or a local foundry to get the correct material. If you cannot
obtain this, you can dilute the liquid sodium silicate with water to reach the desired ratio.
Typical binder levels are between 2-5% by weight of sand. Collapsibility can be improved by
adding 0.25-0.5% by weight of sand of wheat flour, starch, molasses, or oat meal. Carbon
dioxide gas pressure should be between 5-15 psi. Typical gassing times are 5-20 seconds. Thick
cores may require a series of small holes be created in the sand to distribute the CO2.
Mixing Equipment
Sodium silicate can be mixed using a variety of equipment. Small amounts of core sand can be
prepared using heavy duty kitchen stand mixers. These are very suitable for small teaching
foundries. Mullers, high intensity mixers, and continuous mixers are normally used by industry.
Mixing equipment and core boxes should be cleaned immediately with water. If not cleaned,
then a hard, rock-like deposit forms. The deposit can be removed by soaking it with water.
Gassing Equipment
Gassing equipment is relatively simple. A cylinder of CO2 with a regulator and some type of
diffusing system are all that are needed. A simple diffuser system made from an air gun, PVC
end cap, and rubber pipe reducer. Large core boxes should have a cover with a hole for the
CO2to enter and an open cavity above the core sand.
Procedure
1) Measure out sand, sodium silicate binder, and wheat flour.
2) Place the sand in a mixing bowl and mix for 2 minutes. Use setting 2 on the mixer.
3) Add the sodium silicate binder to the sand and mix for 4 minutes.
4) Add your wheat flour and mix for 2 minutes
5) Remove the sand and ram it into the core box.
6) Using the cake tester place several small holes into the sand. The depth of each hole should
be about three quarters of the core thickness
7) Rap the core box prior to gassing.
8) Making sure the CO2gas pressure is 10psi, gas the core for the specified time.
9) Remove the core and any loose sand in the core box.
No bake molds
No bake molds are expendable sand molds, similar to typical sand molds, except they also
contain a quick-setting liquid resin and catalyst. Rather than being rammed, the molding sand is
poured into the flask and held until the resin solidifies, which occurs at room temperature. This
type of molding also produces a better surface finish than other types of sand molds. Because no
heat is involved it is called a cold-setting process. Common flask materials that are used are

34. wood, metal, and plastic. Common metals cast into no bake molds are brass, iron ferrous, and
aluminum alloys.
No-bake Casting
As the metal casting industry’s second favorite method for producing cast components (green
sand molding is the first), no-bake molding has proven its worth as an efficient means to produce
medium and low volumes of complex castings in both ferrous and nonferrous metals.
In the no-bake process, sand is mixed with a chemical binder/catalyst system and then molded
around the cope and drag halves of the tooling. After a specified period of time (from as little as
10 sec to as long as the foundry requires depending upon mold size), the sand mixture hardens
(resembling a brick in strength) to form the mold halves and the tooling is drawn. Then, a
refractory coating may be applied to both mold halves before they are brought together to form
one complete mold for pouring. (No-bake molded cores also can be produced using a similar
method and assembled into the mold to form more complex shapes.)
No-bake molding, like green sand molding, is known for its versatility. Virtually all metals can
be cast via no-bake molding with component weights ranging from less than a pound to several
hundred thousand pounds. For casting designers, no-bake molding offers:
1. good dimensional tolerances (±0.005-0.015) because the rigidity of the mold withstands
the pressures exerted by the molten metal during casting;
2. Compatibility with most pattern materials, including wood, plastic, metal, fiberglass and
Styrofoam, allowing for inexpensive tooling options for casting runs as low as one. In
addition, no-bake molding imparts minimal tooling wear;
3. Design flexibility for intricate casting shapes. The rigidity and tensile strength of no-bake
molds allows for thin sections of 0.1-in. to be routinely produced. In addition, mold
strength allows for minimal draft and radii requirements in casting design.
4. reduced opportunity for gas-related defects as the nitrogen content of most binder
systems used for no-bake molding minimize susceptibility to gas porosity;
5. Fine surface finishes that can be upgraded further with the mold and core coatings to
support special finishing on the cast components such as paint or dressing. In addition,
no-bake casters can alter their molding media make-up from basic silica sand to higher-
end media such as chromite or zircon sand for applications requiring X-ray quality and
extreme pressure tightness;
6. Ability to work well with unique metal casting quality enhancement tools such as metal
filters, ceramic runner systems and exothermic risers to improve casting properties.
7. Low to medium volume production capability with runs from 1-5000 parts/yr.
The key, as with any casting process, is to ensure the casting design is optimized to take
advantage of the benefits afforded by no-bake molding.
No-bake molding typically is an option for production runs from 1-5000 castings/yr . Due to the
curing time required for the chemicals to harden the mold as well as the methods to distribute the
molding media on the pattern, the high productions achievable with green sand, permanent mold

35. or die-casting aren’t possible with nobake. No-bake molding prefers cast components with
higher complexities in low to medium volume runs.
Anything that can be cast in a green sand mold can be cast in a nobake mold, but the reverse isn’t
true. Besides the number of castings that need to be produced, the decision between green sand
and nobake comes down to the complexity of the casting design. Since unfinished nobake
molded castings (without machining) typically cost 20-30% higher than green sand, designers
and purchasers sourcing to nobake molding must offset this price difference by taking advantage
of what the process offers. Significant reductions in machining costs can be achieved through the
process’ tight tolerances and minimal dimensional variability and by designing in complex
shapes and geometries, thin walls, and reduced draft, radii and machine stock.
Tooling cost also plays a factor in this comparison. Green sand molds require compaction force
during the molding process, which means that the tooling must be able to withstand this force.
No-bake tooling doesn’t have to withstand a strong compaction force (often only light
vibrations), allowing wood and plastic to be viable tooling materials. In addition, the lack of
compaction force in molding also allows nobake molders to use loose pattern pieces and other
innovative tooling options to increase casting complexity and add design features to the
components.
Pattern materials for nobake molding include wood, plastic, fiberglass, metal and Styrofoam.
This allows the tooling cost to be minimized as much as if not more than any other production
casting process. In addition, with the Styrofoam option for the Full Mold process hard tooling
doesn’t even have to be created for small production runs.
Designing castings for traditional nobake molding follows many of the same principles used in
all other casting processes. Draft is required so patterns can be drawn, sharp corners and angles
should be minimized and uniform section thicknesses (especially in the same plane) should be
employed as much as possible. However, the process does allow for more daring designs.

36. Mold materials
There are four main components for making a sand casting mold:
1) Base sand 2) A binder 3) Additives 4) A parting compound.
Molding sands
Molding sands, also known as foundry sands, are defined by eight characteristics: 1)
refractoriness 2) chemical inertness 3) permeability, 3) surface finish, 4) cohesiveness, 5)
flowability, 6) collapsibility, 7) availability/cost.
Refractoriness — this refers to the sand's ability to withstand the temperature of the liquid
metal being cast without breaking down. For example some sands only need to withstand 650 °C
(1,202 °F) if casting aluminum alloys, whereas steel needs sand that will withstand 1,500 °C
(2,730 °F). Sand with too low a refractoriness will melt and fuse to the casting.
Chemical inertness — the sand must not react with the metal being cast. This is especially
important with highly reactive metals, such as magnesium and titanium.
Permeability — this refers to the sand's ability to exhaust gases. This is important because
during the pouring process many gases are produced, such as hydrogen, nitrogen, carbon,
and steam, which must leave the mold otherwise casting defects, such as blow holes and gas
holes, occur in the casting. Note that for each cubic centimeter (cc) of water added to the mold
16,000 cc of steam is produced.
Surface finish — the size and shape of the sand particles defines the best surface finish
achievable, with finer particles producing a better finish. However, as the particles become finer
(and surface finish improves) the permeability becomes worse.
Cohesiveness (or bond) — this is the ability of the sand to retain a given shape after the pattern
is removed.
Flowability – The ability for the sand to flow into intricate details and tight corners without
special processes or equipment.
Collapsibility — this is the ability of the sand to be easily stripped off the casting after it has
solidified. Sands with poor collapsibility will adhere strongly to the casting. When casting metals
that contract a lot during cooling or with long freezing temperature ranges sand with poor
collapsibility will cause cracking and hot tears in the casting. Special additives can be used to
improve collapsibility.
Availability/cost — the availability and cost of the sand is very important because for every ton
of metal poured, three to six tons of sand is required. Although sand can be screened and reused,
the particles eventually become too fine and require periodic replacement with fresh sand.
In large castings it is economical to use two different sands, because the majority of the sand will
not be in contact with the casting, so it does not need any special properties. The sand that is in
contact with the casting is called facing sand, and is designed for the casting on hand. This sand
will be built up around the pattern to a thickness of 30 to 100 mm (1.2 to 3.9 in). The sand that
fills in around the facing sand is called backing sand. This sand is simply silica sand with only a
small amount of binder and no special additives.

37. Types of base sands
Base sand is the type used to make the mold or core without any binder. Because it does not have
a binder it will not bond together and is not usable in this state.
Silica sand
Silica (SiO2) sand is the sand found on a beach and is also the most commonly used sand. It is
made by either crushing sandstone or taken from natural occurring locations, such as beaches
and river beds. The fusion point of pure silica is 1,760 °C (3,200 °F), however the sands used
have a lower melting point due to impurities. For high melting point casting, such as steels, a
minimum of 98% pure silica sand must be used; however for lower melting point metals, such
as cast iron and non-ferrous metals, a lower purity sand can be used (between 94 and 98% pure).
Silica sand is the most commonly used sand because of its great abundance, and, thus, low cost
(therein being its greatest advantage). Its disadvantages are high thermal expansion, which can
cause casting defects with high melting point metals, and low thermal conductivity, which can
lead to unsound casting. It also cannot be used with certain basic metal because it will
chemically interact with the metal forming surface defect. Finally, it causes silicosis in foundry
workers.
Olivine sand
Olivine is a mixture of orthosilicates of iron and magnesium from the mineral dunite. Its main
advantage is that it is free from silica; therefore it can be used with basic metals, such as
manganese steels. Other advantages include a low thermal expansion, high thermal conductivity,
and high fusion point. Finally, it is safer to use than silica; therefore it is popular in Europe.
Chromite sand
Chromite sand is a solid solution of spinels. Its advantages are a low percentage of silica, a very
high fusion point (1,850 °C (3,360 °F)), and a very high thermal conductivity. Its disadvantage is
its costliness; therefore it’s only used with expensive alloy steel casting and to make cores.
Zircon sand
Zircon sand is a compound of approximately two-thirds zircon oxide (Zr2O) and one-third silica.
It has the highest fusion point of all the base sands at 2,600 °C (4,710 °F), a very low thermal
expansion, and a high thermal conductivity. Because of these good properties it is commonly
used when casting alloy steels and other expensive alloys. It is also used as a mold wash (a
coating applied to the molding cavity) to improve surface finish. However, it is expensive and
not readily available.
Chamotte sand
Chamotte is made by calcining fire clay (Al2O3-SiO2) above 1,100 °C (2,010 °F). Its fusion point
is 1,750 °C (3,180 °F) and has low thermal expansion. It is the second cheapest sand; however it
is still twice as expensive as silica. Its disadvantages are very coarse grains, which result in a
poor surface finish, and it is limited to dry sand molding. Mold washes are used to overcome the
surface finish problem. This sand is usually used when casting large steel work pieces.
Other materials

38. Modern casting production methods can manufacture thin and accurate molds—of a material
superficially resembling papier-mâché, such as is used in egg cartons, but that is refractory in
nature—that are then supported by some means, such as dry sand surrounded by a box, during
the casting process. Due to the higher accuracy it is possible to make thinner and hence lighter
castings, because extra metal need not be present to allow for variations in the molds. These thin-
mold casting methods have been used since the 1960s in the manufacture of cast-iron engine
blocks and cylinder heads for automotive applications.
Binders
Binders are added to base sand to bond the sand particles together (i.e. it is the glue that holds the
mold together).
Clay and water
A mixture of clay and water is the most commonly used binder. There are two types of clay
commonly used: bentonite and kaolinite, with the former being the most common.
Oil
Oils, such as linseed oil, other vegetable oils and marine oils, used to be used as a binder,
however due to their increasing cost; they have been mostly phased out. The oil also required
careful baking at 100 to 200 °C (212 to 392 °F) to cure (if overheated the oil becomes brittle,
wasting the mold).
Resin
Resin binders are natural or synthetic high melting point gums. The two common types used
are urea formaldehyde (UF) and phenol formaldehyde (PF) resins. PF resins have a higher heat
resistance than UF resins and cost less. There are also cold-set resins, which use
a catalyst instead of a heat to cure the binder. Resin binders are quite popular because different
properties can be achieved by mixing with various additives. Other advantages include good
collapsibility, low gassing, and they leave a good surface finish on the casting.
MDI (methylene diphenyl diisocyanate) is also a commonly used binder resin in the foundry core
process.
Sodium silicate
Sodium silicate [Na2SiO3 or (Na2O)(SiO2)] is a high strength binder used with silica molding
sand. To cure the binder carbon dioxide gas is used, which creates the following reaction:
The advantage to this binder is that it can be used at room temperature and it's fast. The
disadvantage is that its high strength leads to shakeout difficulties and possibly hot tears in the
casting.
Additives
Additives are added to the molding components to improve: surface finish, dry strength,
refractoriness, and "cushioning properties".
Up to 5% of reducing agents, such as coal powder, pitch, creosote, and fuel oil, may be added to
the molding material to prevent wetting (prevention of liquid metal sticking to sand particles,

39. thus leaving them on the casting surface), improve surface finish, decrease metal penetration,
and burn-on defects. These additives achieve this by creating gases at the surface of the mold
cavity, which prevent the liquid metal from adhering to the sand. Reducing agents are not used
with steel casting, because they can carburize the metal during casting.
Up to 3% of "cushioning material", such as wood flour, saw dust, powdered husks, peat,
and straw, can be added to reduce scabbing, hot tear, and hot crack casting defects when casting
high temperature metals. These materials are beneficial because burn-off when the metal is
poured creating voids in the mold, which allow it to expand. They also increase collapsibility and
reduce shakeout time.
Up to 2% of cereal binders, such as dextrin, starch, sulphitelye, and molasses, can be used to
increase dry strength (the strength of the mold after curing) and improve surface finish. Cereal
binders also improve collapsibility and reduce shakeout time because they burn-off when the
metal is poured. The disadvantage to cereal binders is that they are expensive.
Up to 2% of iron oxide powder can be used to prevent mold cracking and metal penetration,
essentially improving refractoriness. Silica flour (fine silica) and zircon flour also improve
refractoriness, especially in ferrous castings. The disadvantages to these additives are that they
greatly reduce permeability.
Parting compounds
To get the pattern out of the mold, prior to casting, a parting compound is applied to the pattern
to ease removal. They can be a liquid or a fine powder (particle diameters between 75 and 150
micrometers (0.0030 and 0.0059 in)). Common powders include talc, graphite, and dry silica;
common liquids include mineral oil and water-based silicon solutions. The latter are more
commonly used with metal and large wooden patterns.
Sand Reclamation
Sand Reclamation can be termed as the process of reconditioning of used sand in a foundry
without lowering its original properties, which are particularly required for foundry application.
Reclamation process for foundry sand is broadly of two types – Mechanical (Attrition) and
Thermal.
Thermal Reclamation is the process in which the sand is heated to a temperature of about 800
deg. C, in a specially designed fluidized bed Combustor which is the main equipment of the
thermal reclamation system. Thermal reclamation is, in many ways, better than attrition
(mechanical) reclamation process, for the following reasons:
1. New sand has higher thermal expansion. During pouring, the mould expands excessively
and causes distortion, instability and dimensional inaccuracy. When sand is heated above
600 Deg. C, the same undergoes phase change which is permanent in nature. This phase-
changed sand has lower thermal expansion and, therefore, all the problems mentioned
above are less.
2. Unlike mechanical reclamation, 100% sand, except those reduced to dust, is reclaimed to
better-than-new condition.
In the Thermal Reclaimer, the sand grains obtained after breaking the lumps are pre-heated in a
heat exchanger and fed into the Combustor at a pre-determined rate. Here it is fluidized by

40. precisely controlled air. The fluidized bed of sand receives controlled stream of flame and hot
products of combustion from a specially designed LPG / Natural gas combustion system. The
binder in the sand is totally burnt and hot reclaimed sand is obtained at the outlet of the
Combustor. The hot sand from the Combustor is transported to a bunker and then made to pass
through a Fluidized Bed Cooler having a water cooling system. The cooler is also connected with
a dust extraction system for classification of sand. The reclaimed sand, cooled down to usable
temperature and classified, is then pneumatically transported to the sand bunker for re-use.
Thermal Sand Reclaimer is field tested and has been found to consume only 7 to 9 Kg of LPG
per MT of sand. Though it is better to use Natural gas or LPG, the reclaimer can be fired with
Light oil where the gaseous fuel is not available. Thermal Sand Reclaimer can be used for
reclaiming Shell sand, Phenolic 2-part/3-part sand, Furan sand etc. Even Green sand may be
reclaimed with additional downstream equipment.
Pouring
In a foundry, molten metal is poured into molds. Pouring can be accomplished with gravity, or it
may be assisted with a vacuum or pressurized gas. Many modern foundries use robots or
automatic pouring machines for pouring molten metal. Traditionally, molds were poured by hand
using ladles.
Shakeout
The solidified metal component is then removed from its mold. Where the mold is sand based,
this can be done by shaking or tumbling. This frees the casting from the sand, which is still
attached to the metal runners and gates - which are the channels through which the molten metal
traveled to reach the component itself.
Degating
Degating is the removal of the heads, runners, gates, and risers from the casting. Runners, gates,
and risers may be removed using cutting torches, band saws or ceramic cutoff blades. For some
metal types, and with some gating system designs, the sprue, runners and gates can be removed
by breaking them away from the casting with a sledge hammer or specially designed knockout
machinery. Risers must usually be removed using a cutting method but some newer methods of
riser removal use knockoff machinery with special designs incorporated into the riser neck
geometry that allow the riser to break off at the right place.
The gating system required to produce castings in a mold yields leftover metal, including heads,
risers and sprue, sometimes collectively called sprue that can exceed 50% of the metal required
to pour a full mold. Since this metal must be remelted as salvage, the yield of a particular gating
configuration becomes an important economic consideration when designing various gating
schemes, to minimize the cost of excess sprue, and thus melting costs.

41. Heat treating
Heat treating is a group of industrial and metalworking processes used to alter the physical, and
sometimes chemical, properties of a material. The most common application is metallurgical.
Heat treatments are also used in the manufacture of many other materials, such as glass. Heat
treatment involves the use of heating or chilling, normally to extreme temperatures, to achieve a
desired result such as hardening or softening of a material. Heat treatment techniques include
annealing, case hardening, precipitation strengthening, tempering and quenching. It is
noteworthy that while the term heat treatment applies only to processes where the heating and
cooling are done for the specific purpose of altering properties intentionally, heating and cooling
often occur incidentally during other manufacturing processes such as hot forming or welding.
Surface cleaning
After degating and heat treating, sand or other molding media may adhere to the casting. To
remove this surface is cleaned using a blasting process. This means a granular media will be
propelled against the surface of the casting to mechanically knock away the adhering sand. The
media may be blown with compressed air, or may be hurled using a shot wheel. The media
strikes the casting surface at high velocity to dislodge the molding media (for example, sand,
slag) from the casting surface. Numerous materials may be used as media, including steel, iron,
other metal alloys, aluminium oxides, glass beads, walnut shells, baking powder among others.
The blasting media is selected to develop the color and reflectance of the cast surface. Terms
used to describe this process include cleaning, bead blasting, and sand blasting. Shot
peening may be used to further work-harden and finish the surface.
Finishing
The final step in the process usually involves grinding, sanding, or machining the component in
order to achieve the desired dimensional accuracies, physical shape and surface finish.
Removing the remaining gate material, called a gate stub, is usually done using
a grinder or sanding. These processes are used because their material removal rates are slow
enough to control the amount of material. These steps are done prior to any final machining.
After grinding, any surfaces that require tight dimensional control are machined. Many castings
are machined in CNC milling centers. The reason for this is that these processes have better
dimensional capability and repeatability than many casting processes. However, it is not
uncommon today for many components to be used without machining.
A few foundries provide other services before shipping components to their customers. Painting
components to prevent corrosion and improve visual appeal is common. Some foundries will
assemble their castings into complete machines or sub-assemblies. Other foundries weld multiple
castings or wrought metals together to form a finished product.

42. More and more the process of finishing a casting is being achieved using robotic machines which
eliminate the need for a human to physically grind or break parting lines, gating material or
feeders. The introduction of these machines has reduced injury to workers, costs of consumables
whilst also reducing the time necessary to finish a casting. It also eliminates the problem of
human error so as to increase repeatability in the quality of grinding. With a change of tooling
these machines can finish a wide variety of materials including iron, bronze and aluminium.
CAST IRON
Cast iron is iron or a ferrous alloy which has been heated until it liquefies, and is then poured
into a mould to solidify. It is usually made from pig iron. The alloy constituents affect its color
when fractured: white cast iron has carbide impurities which allow cracks to pass straight
through. Grey cast iron has graphite flakes which deflect a passing crack and initiate countless
new cracks as the material breaks.
Carbon (C) and silicon (Si) are the main alloying elements, with the amount ranging from 2.1–
4 wt% and 1–3 wt%, respectively. Iron alloys with less carbon content are known as steel. While
this technically makes these base alloys ternary Fe–C–Si alloys, the principle of cast iron
solidification is understood from the binary iron–carbon phase diagram. Since the compositions
of most cast irons are around the eutectic point of the iron–carbon system, the melting
temperatures closely correlate, usually ranging from 1,150 to 1,200 °C (2,100 to 2,190 °F),
which is about 300 °C (572 °F) lower than the melting point of pure iron.
Cast iron tends to be brittle, except for malleable cast irons. With its relatively low melting point,
good fluidity, cast-ability, excellent machinability, resistance to deformation and wear resistance,
cast irons have become an engineering material with a wide range of applications and are used in
pipes, machines and automotive industry parts, such as cylinder heads (declining usage), cylinder
blocks and gearbox cases (declining usage). It is resistant to destruction and weakening
by oxidation (rust).
The earliest cast iron artifacts date to the 5th century BC, and were discovered
by archaeologists in what is now modern Luhe County, Jiangsu in China. Cast iron was used in
ancient China for warfare, agriculture, and architecture. During the 15th century, cast iron
became utilized for artillery in Burgundy, France, and in England during the Reformation. The
first cast iron bridge was built during the 1770s by Abraham Darby III, and is known as The Iron
Bridge. Cast iron is also used in the construction of buildings.
Grey cast iron is characterized by its graphitic microstructure, which causes fractures of the
material to have a grey appearance. It is the most commonly used cast iron and the most widely
used cast material based on weight. Most cast irons have a chemical composition of 2.5–4.0%
carbon, 1–3% silicon, and the remainder is iron. Grey cast iron has less tensile

43. strength and shock resistance than steel, but its compressive strength is comparable to low and
medium carbon steel. Its melting point is 1093 degree C-1315 degree C.
Ductile cast iron
A more recent development is nodular or ductile cast iron. Tiny amounts
of magnesium or cerium added to these alloys slow down the growth of graphite precipitates by
bonding to the edges of the graphite planes. Along with careful control of other elements and
timing, this allows the carbon to separate as spheroidal particles as the material solidifies. The
properties are similar to malleable iron, but parts can be cast with larger sections. 1120 degree
Celsius-1176 degree C melting point. Gray iron, or grey iron, is a type of cast iron that has
a graphitic microstructure. It is named after the gray color of the fracture it forms, which is due
to the presence of graphite. It is the most common cast iron and the most widely used cast
material based on weight. It is used for housings where tensile strength is non-critical, such
as internal combustion engine cylinder blocks, pump housings, valve bodies, electrical boxes,
and decorative castings. Grey cast iron's high thermal conductivity and specific heat capacity are
often exploited to make cast iron cookware and disc brake rotors.
Structure
A typical chemical composition to obtain a graphitic microstructure is 2.5 to 4.0% carbon and 1
to 3% silicon. Silicon is important to making grey iron as opposed to white cast iron, because
silicon is a graphite stabilizing element in cast iron, which means it helps the alloy produce
graphite instead of iron carbides. Another factor affecting graphitization is the solidification rate;
the slower the rate, the greater the tendency for graphite to form. A moderate cooling rate forms
a more pearlitic matrix, while a fast cooling rate forms a more ferritic matrix. To achieve a fully
ferritic matrix the alloy must be annealed. Rapid cooling partly or completely suppresses
graphitization and leads to formation of cementite, which is called white iron.
The graphite takes on the shape of a three-dimensional flake. In two dimensions, as a polished
surface will appear under a microscope, the graphite flakes appear as fine lines. The graphite has
no appreciable strength, so they can be treated as voids. The tips of the flakes act as preexisting
notches; therefore, it is brittle. The presence of graphite flakes makes the Grey Iron easily
machinable as they tend to crack easily across the graphite flakes. Grey iron also has very good
damping capacity and hence it is mostly used as the base for machine tool mountings.
Classifications
In the United States, the most commonly used classification for gray iron is ASTM
International standard A48. This classifies gray iron into classes which corresponds with its
minimum tensile strength in thousands of pounds per square inch (ksi); e.g. class 20 gray iron
has a minimum tensile strength of 20,000 psi (140 MPa). Class 20 has a high carbon
equivalent and a ferrite matrix. Higher strength gray irons, up to class 40, have lower carbon
equivalents and a pearlite matrix. Gray iron above class 40 requires alloying to provide solid
solution strengthening, and heat treating is used to modify the matrix. Class 80 is the highest

44. class available, but it is extremely brittle. ASTM A247 is also commonly used to describe the
graphite structure. Other ASTM standards that deal with gray iron include ASTM A126, ASTM
A278, and ASTM A319.
In the automotive industry the SAE International (SAE) standard SAE J431 is used to
designate grades instead of classes. These grades are a measure of the tensile strength-to-Brinell
hardness ratio.
Advantages and disadvantages
Gray iron is a common engineering alloy because of its relatively low cost and
good machinability, which results from the graphite lubricating the cut and breaking up the
chips. It also has good galling and wears resistance because the graphite flakes self lubricate. The
graphite also gives gray iron an excellent damping capacity because it absorbs the energy.
Gray iron also experiences less solidification shrinkage than other cast irons that do not form a
graphite microstructure. The silicon promotes good corrosion resistance and increase fluidity
when casting. Gray iron is generally considered easy to weld. Compared to the more modern iron
alloys, gray iron has a low tensile strength and ductility; therefore, its impact and shock
resistance is almost non-existent.
Ductile iron, also known as ductile cast iron, nodular cast iron, spheroidal graphite
iron, spherulitic graphite cast iron and SG iron, is a type of cast iron invented in 1943 by Keith
Millis. While most varieties of cast iron are brittle, ductile iron has much more impact and
fatigue resistance, due to its nodular graphite inclusions.
Properties of ASTM A48 classes of gray iron
Class
Tensile
strength [ksi]
Compressive
strength [ksi]
Tensile modulus
(E) [106 psi]
20 22 33 10
30 31 109 14
40 57 140 18
60 62.5 187.5 21
Properties of SAE J431 grades of gray iron
Grade Brinell hardness t/h† Description
G1800 120–187 135 Ferritic-pearlitic
G2500 170–229 135 Pearlitic-ferritic
G3000 187–241 150 Pearlitic
G3500 207–255 165 Pearlitic
G4000 217–269 175 Pearlitic
†t/h = tensile strength/hardness

45. Ductile iron microstructure at 100×. Note carbon islanding effect around
nodules.
Ductile iron is not a single material but is part of a group of materials which can be produced to
have a wide range of properties through control of the microstructure. The common defining
characteristic of this group of materials is the shape of the graphite. In ductile irons, the graphite
is in the form of nodules rather than flakes as it is in grey iron. The sharp shape of the flakes of
graphite create stress concentration points within the metal matrix and the rounded shape of the
nodules less so, thus inhibiting the creation of cracks and providing the enhanced ductility that
gives the alloy its name. The formation of nodules is achieved by the addition of nodulizing
elements, most commonly magnesium (note magnesium boils at 1100°C and iron melts at
1500°C) and, less often now, cerium (usually in the form of Mischmetal). Tellurium has also
been used. Yttrium, often a component of Misch metal, has also been studied as a possible
nodulizer.
"Austempered Ductile Iron" (ADI) was invented in the 1950s but was commercialized and
achieved success only some years later. In ADI, the metallurgical structure is manipulated
through a sophisticated heat treating process. The "aus" portion of the name refers to austenite.
Composition
A typical chemical analysis of this material:
 Carbon 3.3 to 3.4%
 Silicon 2.2 to 2.8%
 Manganese 0.1 to 0.5%
 Magnesium 0.03 to 0.05%
 Phosphorus 0.005 to 0.04%
 Sulfur 0.005 to 0.02%
 Iron balance

46. Other elements such as copper or tin may be added to increase tensile and yield strength while
simultaneously reducing ductility. Improved corrosion resistance can be achieved by replacing
15% to 30% of the iron in the alloy with varying amounts of nickel, copper, or chromium.
Applications
Much of the annual production of ductile iron is in the form of ductile iron pipe, used for water
and sewer lines. It competes with polymeric materials such as PVC, HDPE, LDPE
and polypropylene, which are all much lighter than steel or ductile iron, but which, being
flexible, require more careful installation and protection from physical damage.
Ductile iron is specifically useful in many automotive components, where strength needs surpass
that of aluminum but do not necessarily require steel. Other major industrial applications include
off-highway diesel trucks, Class 8 trucks, agricultural tractors, and oil well pumps.
Gray Iron
Cast irons are alloys of iron, carbon, and silicon in which more carbon is present than can be
retained in solid solution in austenite at the eutectic temperature. In gray cast iron, the carbon
that exceeds the solubility in austenite precipitates as flake graphite. Gray irons usually contain
2.5 to 4% C, 1 to 3% Si, and additions of manganese, depending on the desired microstructure
(as low as 0.1% Mn in ferritic gray irons and as high as 1.2% in pearlitics). Sulphur and
phosphorus are also present in small amounts as residual impurities.
Cast irons are alloys of iron, carbon, and silicon in which more carbon is present than can be
retained in solid solution in austenite at the eutectic temperature. In gray cast iron, the carbon
that exceeds the solubility in austenite precipitates as flake graphite.
Gray irons usually contain 2.5 to 4% C, 1 to 3% Si, and additions of manganese, depending on
the desired microstructure (as low as 0.1% Mn in ferritic gray irons and as high as 1.2% in
pearlitics). Sulphur and phosphorus are also present in small amounts as residual impurities.
The composition of gray iron must be selected in such a way to satisfy three basic structural
requirements:
 The required graphite shape and distribution
 The carbide-free (chill-free) structure
 The required matrix
For common cast iron, the main elements of the chemical composition are carbon and silicon.
High carbon content increases the amount of graphite or Fe3C. High carbon and silicon contents
increase the graphitization potential of the iron as well as its castability.
The combined influence of carbon and silicon on the structure is usually taken into account by
the carbon equivalent (CE):
CE = %C + 0.3 x (%Si) + 0.33 x (%P) - 0.027 x (%Mn) + 0.4 x (%S)