When What with road They

1.  Manufacturing cast iron
 History
 The first known cupola furnace was made by René-
Antoine Ferchault de Réaumur around 1720, though
evidence suggests that this technique was in use in China
as far back as the 3rd and 2nd centuries BC.
 For many years, the Cupola served as the work
horse of the cast iron industry
 The Cupola is round and tall.
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2. Pictorial representation of the gas recovery cupola.
Source: Central Foundry, Division of General Motors
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3. Working of Cupola Furnace
 Starting the Cupola Furnace
 Initially, soft and dry wooden pieces are placed
on the sand bottom after which coke is charged up
to the tuyeres lever. The wooden pieces are ignited
through the tap hole and sufficient air is passed
through the tuyeres for proper combustion of coke.
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4.  Charging Cupola Furnace
 The charge used in cupola furnace consists of
alternate layers of coke, flux and metal (iron).
These three components are continuously built into
the cupola furnace.
 The most commonly used iron - to - coke ratio is
8:1. The flux may be limestone (CaCO3), fluorspar,
sodium carbonate or calcium carbide. Limestone is
the commonly employed flux. The total weight of
the flux will be approximately 1/5th the weight of
the coke charge.
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6.  Melting in Cupola Furnace
 Cupola furnace works on the counter current
principle. As the combustion takes place, the
charge materials (coke, flux and metal) will be
descending downwards, while the hot gases due
to combustion will be ascending upwards.
 Heat exchange takes place between the rising
hot gases and the descending charge thereby
melting the metal. The liquid metal drops down,
while the coke floats up on top of it.
 The flux also melts and reacts with the
impurities of the molten metal forming a slag. The
slag floats on the surface of the molten metal
thereby preventing oxidation of the metal.
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7. A cupola furnace in operation at Wayne State University, in Detroit, Michigan 7

8. Tapping slag and molten metal
in Cupola Furnace
 When sufficient liquid metal is collected in the reservoir,
the slag door is opened and the slag floating on the
surface of the molten metal is tapped and disposed off.
 Immediately the tapping is opened and the liquid metal
is tapped into ladles. The tapping spout is again closed.
 The liquid metal from the ladle is poured into the moulds.
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9.  Zones of Cupola Furnace
 Well zone in Cupola Furnace:-
 Well zone in the portion situated between the rammed
sand bottom and just below the bottom edge of the tuyeres.
The molten metal is occupied in this zone.
 Combustion Zone in Cupola Furnace
 The combustion zone or oxidizing zone is situated normally
15-30 cm from the bottom edge of the tuyeres. It is in this
zone where rapid combustion of coke takes place due to
which a lot of heat is generated in the furnace. The
combustion is rapid due to the supply of blast air through the
tuyeres.
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10.  Combustion Zone in Cupolacon/d.
 Oxidation of manganese and silicon evolve still
more heat. The reactions which take place in this zone
are:
C+O2 (from air) → CO2+heat
2Mn+O2 → 2MnO+heat
Si+O2 → SiO2+heat
 The temperature in this zone varies from 1550C -
1850C
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11.  Reducing Zone in Cupola Furnace
 Reducing zone or protection zone is the portion located from the top
of the combustion zone to the top of the coke bed.
 In this zone, some of the hot CO2 gas moving upward through the
hot coke gets reduced to CO.
 In other words, reduction of CO2 to CO occurs in this zone. Due to
the reducing atmosphere, the charge is protected from oxidation.
 The reaction taking place in this zone is given by.
CO2+C (coke)à2CO - Heat
 Due to the reduction, the temperature reduces to around 1200 C in
this zone.
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12.  Melting Zone in Cupola Furnace
The portion located just above the coke bed to the
top of the metal (iron) is called the melting zone.
 The metal starts melting in this zone and trickles
down through the coke bed to the well zone.
 The molten iron while passing down through the
reducing zone picks up carbon and the reaction
is given by:
3Fe+2CO → Fe3C+ CO2
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13.  Preheating zone in Cupola Furnace
 The portion occupied from the top surface of the
melting zone to the
 charging door is called ‘Preheating zone’.
The hot gases rising upwards from the combustion
and reducing zone gives its heat to the charge before
passing out of the furnace.
Thus, the charge is preheated before descending
downwards.
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14.  Advantages of Cupola Furnace
 The cupola furnace has received a lot of negative
publicity in recent years. However, the system does have
a number of inherent advantages over electric furnaces:
• It is simple and economical to operate.
A cupola is capable of accepting a wide range of
materials without reducing melt quality. Dirty, oily scrap
can be melted as well as a wide range of steel and iron.
They therefore play an important role in the metal
recycling industry
• Cupolas can refine the metal charge, removing
impurities out of the slag.
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15. Advantages of Cupola con/d.
• From a life-cycle perspective, cupolas are more
efficient and less harmful to the environment than
electric furnaces. This is because they derive energy
directly from coke rather than from electricity that
first has to be generated.
• High melt rates
• Relatively low operating costs Ease of operation
• The continuous rather than batch process suits the
demands of a repetition foundry.
• Cupolas can be used to reuse foundry by-products
and to destroy other pollutants such as VOC from
the core-making area.
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16.  Electric Induction Furnaces
 Electric induction furnaces are the highly used
furnaces for melting iron and non ferrous alloys.
 As compared to other cupola furnaces, these
furnaces are pollution free and have outstanding
metallurgical control. They are available in capacity
ranging from a few kilograms to 75 tones.
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20. Alloy cast irons
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