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8/16/2019 In Metalworking

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THE MAKING OF METALLIC BODY

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.

Casting processes have been known for thousands of years, and widely used for sculpture,

especially in brone, jewellery in precious metals, and weapons and tools. Traditional techniques

include lost!wax casting, plaster mold casting and sand casting.

The modern casting process is subdivided into two main categories" expendable and non!

expendable casting. It is further broken down by the mold material, such as sand or metal, and

pouring method, such as gravity, vacuum, or low pressure.

Some general mechanical terms!

Fo"n#r$!The place where jobs are prepared by melting and pouring the molten metals into

mould%

Mo"l#!It is a cavity so prepared that it can be used to make castings by pouring molten metal

into it%

&attern!It is a model of anything which is used to prepare moulds by placing it into sands%

MOLD CASTINGS

F"rnace

In Kalsi Metal 'or(s &)T%LTD,they are having a C"*ola +"rnace which is used to melt the

metals for reshaping as desired parts of motor of different sies such as end rings, top cover,

stator core ,stator outer body etc. are made in this department.

#urnace installed in this industry is #urnace,is a type of crucible furnaces .these are the most

commonly used furnace in foundries. In this furnace whole melting of metal is carried out inside

a melting pot, called Crucibles

C"*ola +"rnace

$ c"*ola or c"*ola +"rnace is a melting device used in foundries that can be used to melt cast

iron, ni!resist iron and some brones. The cupola can be made almost any practical sie. The sie

of a cupola is expressed in diameters and can range from %.& to %' feet ().& to *.) m+. The


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overall shape is cylindrical and the equipment is arranged vertically, usually supported by four

legs. The overall look is similar to a large smokestack.

The bottom of the cylinder is fitted with doors which swing down and out to drop bottom. The

top where gases escape can be open or fitted with a cap to prevent rain from entering the cupola.

To control emissions a cupola may be fitted with a cap that is designed to pull the gases into a

device to cool the gases and remove particulate matter.

The shell of the cupola, being usually made of steel, has refractory brick and plastic

refractory patching material lining it. The bottom is lined in a similar manner but often a clay and

sand mixture (-bod-+ may be used, as this lining is temporary. #inely divided coal (-sea coal-+

can be mixed with the clay lining so when heated the coal decomposes and the bod becomes

slightly friable, easing the opening up of the tap holes The bottom lining is compressed or

rammed against the bottom doors. ome cupolas are fitted with cooling jackets to keep the sides

cool and with oxygen injection to make the coke fire burn hotter.

To begin a production run, called a cupola campaign, the furnace is filled with layers of coke

and ignited with torches. ome smaller cupolas may be ignited with wood to start the coke

burning. /hen the coke is ignited, air is introduced to the coke bed through ports in the sides

called tuyeres.

/hen the coke is very hot, solid pieces of metal are charged into the furnace through an opening

in the top. The metal is alternated with additional layers of fresh coke. 0imestone is added to act

as a flux. $s the heat rises within the stack the metal is melted. It drips down through the coke

bed to collect in a pool at the bottom, just above the bottom doors. 1uring the melting processa thermodynamic reaction takes place between the fuel and the blast air. The carbon in the coke

combines with the oxygen in the air to form carbon monoxide. The carbon monoxide further

burns to form carbon dioxide. ome of the carbon is picked up by the falling droplets of molten

metal which raises the carbon content of the iron. ilicon carbide and ferromanganese briquettes

may also be added to the charge materials. The silicon carbide dissociates and carbon and silicon

enters into the molten metal. 0ikewise, the ferromanganese melts and is combined into the pool

of liquid iron in the well at the bottom of the cupola. $dditions to the molten iron such

as ferromanganese, ferrosilicon, ilicon carbide and other alloying agents are used to alter the

molten iron to conform to the needs of the castings at hand.

The operator of the cupola is known as the -cupola tender- or -furnace master-. 1uring the

operation of a tapped cupola (cupolas may vary in this regard+ the tender observes the amount of

iron rising in the well of the cupola. /hen the metal level is sufficiently high, the cupola tender

opens the -tap hole- to let the metal flow into a ladle or other container to hold the molten metal.

/hen enough metal is drawn off the -tap hole- is plugged with a refractory plug made of clay.


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The cupola tender observes the furnace through the sight glass or peep sigh in the tuyeres. lag

will rise to the top of the pool of iron being formed. $ slag hole, located higher up on the

cylinder of the furnace, and usually to the rear or side of the tap hole, is opened to let the slag

flow out. The viscosity is low (with proper fluxing+ and the red hot molten slag will flow easily.

ometimes the slag which runs out the slag hole is collected in a small cup shaped tool, allowed

to cool and harden. It is fractured and visually examined. /ith acid refractory lined cupolas a

greenish colored slag means the fluxing is proper and adequate. In basic refractory lined cupolas

the slag is brown.

Equipments used for casting

Metal "se# ! Cast iron at %23) ,C

Mo"l#ing Bo-es

4old boxes are also known as molding flasks. O*en mol#ing .o-es are made with the hinge at

one corner and a lock on the opposite corner. They are also known as snap molding boxes which

are generally used for making sand molds. $ snap molding is made of wood and is hinged at one

corner. It has special applications in bench molding in green sand work for small nonferrouscastings. The mold is first made in the snap flask and then it is removed and replaced by a steel

jacket. Thus, a number of molds can be prepared using the same set of boxes. $s an alternative to

the wooden snap boxes the cast!aluminum tapered closed boxes are finding favor in modernfoundries. They carry a tapered inside surface which is accurately ground and finished. $ solid

structure of this box gives more rigidity and strength than the open type. These boxes are also

removed after assembling the mould. 0arge molding boxes are equipped with reinforcing cross

bars and ribs to hold the heavy mass if sand and support gaggers. The sie, material andconstruction of the molding box depend upon the sie of the casting.

5pen molding box

La#le

It is similar in shape to the crucible which is also made from graphite or steel shell lined with

suitable refractory material like fire clay. It is commonly used to receive molten metal from the


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melting furnace and pour the same into the mold cavity. Its sie is designated by its capacity.

mall hand shank ladles are used by a single foundry personal and are provided with only one

handle.

0adle

Mol#ing San#

4olding and is a mixture of silica sand with the coal powder along with batanoute ,dextrin

powder ilica sand in form of granular quarts is the main constituent of molding sand havingenough refractoriness which can impart stability and permeability to molding and core sand. 6ut

along with silica small amounts of iron oxide, alumina, lime stone, magnesia, soda and potash

are present as impurities. The chemical composition of silica sand gives an idea of the impuritieslike lime, magnesia, alkalis etc. present. The presence of excessive amounts of iron oxide, alkali

oxides and lime can lower the fusion point to a considerable extent which is undesirable. To

remove these impurities and to minimie the effect of these impurities, doping is made and to provide strength to sand .

Sho/el

It consists of an steel pan fitted with a long wooden handle.It is used in mixing, tempering and

conditioning the foundry sand by hand. It is also used for moving and transforming the molding

sand to the container and molding box or flask. It should always be kept clean.

hovel

Stri(e o++ .ar

It is a flat bar having straight edge and is made of wood or iron.It is used to strike off or remove

the excess sand from the top of a molding box after completion of ramming thereby making its

surface plane and smooth. Its one edge is made beveled and the other end is kept perfectlysmooth and plane.


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trike off bar

DESIGN CONSIDE0ATIONS IN &ATTE0N MAKING

The following considerations should always be kept in mind while designing a pattern"

%. 7arting line should be selected carefully, so as to allow as small portion of the pattern as far as possible in the cope area.

2. The thickness and section of the pattern should be kept as uniform as possible.

'. harp corners and edges should be supported by suitable fillets or otherwise rounded of. It will

facilitate easy withdrawal of pattern, smooth flow of molten metal and ensure a sound casting.

*. urfaces of the casting which are specifically required to be perfectly sound and clean should

be so designed that they will be molded in the drag because the possible defects due to loosesand and inclusions will occur in the cope.

&. $s far as possible, full cores should be used instead of cemented half cores for reducing costand for accuracy.

3. #or mass production, the use of several patterns in a mound with common riser is to be preferred.

8. The pattern should have very good surface finish as it directly affects the corresponding finishof the casting.

9. hape and sie of the casting and that of the core should be carefully considered to decide the

sie and location of the core prints.

:. 7roper material should always be selected for the pattern after carefully analying the factors

responsible for their selection.

%). /herever there is a sharp corner, a fillet should be provided, and the corners maybe rounded

up for easy withdrawal of patterns as well as easy flow of molten metal in the mould.

&ATTE0N LAYO1T

$fter deciding the molding method and form of pattern, planning for the development of complete pattern is made which may be in two different stages. The first stage is to prepare

layout of the different parts of the pattern. The next stage is to shape them. The layout

preparation consists of measuring, marking, and setting out the dimensions on a layout board


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including needed allowances. The first step in laying out is to study the working drawing

carefully and select a suitable board of wood that can accommodate at least two views of the

same on full sie scale. The next step is to decide a working face of the board and plane anadjacent edge smooth and square with the said face. elect a proper contraction scale for

measuring and marking dimensions according to the material of the casting. #urther the layout is

prepared properly and neatly using different measuring and making tools specifying the locationsof core prints and machined surfaces. #inally on completion of the layout, check carefully the

dimension and other requirements by incorporating all necessary pattern allowances before

starting construction of the pattern.

&ATTE0N CONST01CTION

5n preparing the pattern layout, the construction for making it is started by studying the layoutand deciding the location of parting surfaces. #rom the layout, try to visualie the shape of the

pattern and determine the number of separate pieces to be made and the process to be employed

for making them. Then the main part of pattern body is first constructed using pattern making

tools. The direction of wood grains is kept along the length of patterns far as possible to ensuredue strength and accuracy. #urther cut and shape the other different parts of pattern providing

adequate draft on them. The prepared parts are then checked by placing them over the preparedlayout. #urther the different parts of the pattern are assembled with the main body in proper

position by gluing or by means of dowels as the case may be. ;ext the relative locations of all

the assembled parts on the pattern are adjusted carefully. Then, the completed pattern is checkedfor accuracy. ;ext all the rough surfaces of pattern are finished and imparted with a thin coating

of shellac varnish. The wax or leather fillets are then fitted wherever necessary. /ooden fillets

should also be fitted before sanding and finishing. The pattern surface once again prepared for

good surface and give final coat of shellac. #inally different parts or surfaces of pattern arecolored with specific colors mixed in shellac or by painting as per coloring specifications.


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Metal Ma(ing .$ metal casting

The hot molten metal obtained from furnace is obtained in ladle upto caryable capacity of

workers to handle the ladle carefully it is transported to cavity cell manually by workers and it is

poured in the mold slowly!slowly in the mould as iot is poured in the mould the gases present in

the sand of mold burns out as burns flame through the openings provided by rimmers if they arenot provided then the mould will burst out due such a high pressure

Then the desired piece is isolated for %!2 days allowing it to cool down and attain the shape of

the mould . after the time the sand should be remove carefully without damaging the the piece.

Die!casting

1ie casting means casting of the metallic part by making is die where die is a mould cavity of the

shape of metal to make

Die casting is a metal casting process that is characteried by forcing molten metal under high

pressure into a mold cavity. The mold cavity is created using two hardened tool steel dies which

have been machined into shape and work similarly to an injection mold during the process. 4ostdie castings are made from non!ferrous metals,

specificallyinc, copper , aluminium, magnesium, lead, pewter and tin based alloys. 1epending

on the type of metal being cast, a hot! or cold!chamber machine is used.

The casting equipment and the metal dies represent large capital costs and this tends to limit the

process to high volume production. 4anufacture of parts using die casting is relatively simple,

involving only four main steps, which keeps the incremental cost per item low. It is especially

suited for a large quantity of small to medium!sied castings, which is why die casting produces

more castings than any other casting process. 1ie castings are characteried by a very

good surface finish (by casting standards+ and dimensional consistency.
https://en.wikipedia.org/wiki/Metal_castinghttps://en.wikipedia.org/wiki/Metal_castinghttps://en.wikipedia.org/wiki/Molten_metalhttps://en.wikipedia.org/wiki/Mold_cavityhttps://en.wikipedia.org/wiki/Tool_steelhttps://en.wikipedia.org/wiki/Injection_moldinghttps://en.wikipedia.org/wiki/Ferroushttps://en.wikipedia.org/wiki/Zinchttps://en.wikipedia.org/wiki/Zinchttps://en.wikipedia.org/wiki/Copperhttps://en.wikipedia.org/wiki/Aluminiumhttps://en.wikipedia.org/wiki/Magnesiumhttps://en.wikipedia.org/wiki/Magnesiumhttps://en.wikipedia.org/wiki/Leadhttps://en.wikipedia.org/wiki/Leadhttps://en.wikipedia.org/wiki/Pewterhttps://en.wikipedia.org/wiki/Tinhttps://en.wikipedia.org/wiki/Surface_finishhttps://en.wikipedia.org/wiki/Molten_metalhttps://en.wikipedia.org/wiki/Mold_cavityhttps://en.wikipedia.org/wiki/Tool_steelhttps://en.wikipedia.org/wiki/Injection_moldinghttps://en.wikipedia.org/wiki/Ferroushttps://en.wikipedia.org/wiki/Zinchttps://en.wikipedia.org/wiki/Copperhttps://en.wikipedia.org/wiki/Aluminiumhttps://en.wikipedia.org/wiki/Magnesiumhttps://en.wikipedia.org/wiki/Leadhttps://en.wikipedia.org/wiki/Pewterhttps://en.wikipedia.org/wiki/Tinhttps://en.wikipedia.org/wiki/Surface_finishhttps://en.wikipedia.org/wiki/Metal_casting

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