MELTING FURNACES
Various type of furnaces used in Foundry. The selection of the furnace depends on the type of metal to be melt and the quantity of metal to be melt.
The metal melting furnace used are
1. Cupola furnace
2. Open hearth furnace
3. Crucible furnace (1.Pit type furnaces, 2. Coke fired stationary furnaces 3. Oil fired tilting furnaces )
4. Pot Furnace
5. Electric Furnace ( 1. Direct arc furnace , 2. Indirect arc furnace, 3. Induction furnace )
CUPOLA FURNACE
This furnace used for melting Cast Iron
A cupola or cupola furnace is a melting device used in foundries that can be used to melt cast iron, ni-resist iron and some bronzes. The cupola can be made almost any practical size. The size of a cupola is expressed in diameters and can range from 1.5 to 13 feet (0.5 to 4.0 m). The overall shape is cylindrical and the equipment is arranged vertically, usually supported by four legs. The overall look is similar to a large smokestack.
construction
Vertical cylindrical shell made out of 10mm thick steel plate. Inside is lined with refractory bricks . Two bottom door closes the Cupola furnace. Sand bed is laid over the bottom door. This sand bed slopes towards the tap hole. Molten metal stays over this bed. Concrete legs are set at the bottom of the Cupola furnace. Tape hole is provided to take out the molten metal. A plug made out of clay closes the tape hole. The slag floating over the molten metal is removed through this slag hole.
One meter above the bottom opening called tuyeres are provided to feed fuel for complete combustion of fuel. There is a wind box and blower to supply air for combustion. For charging fuel and metal a separate charging door is provided.
Preparation
Waste and slag of previous melting is cleaned using the bottom of the cylinder which is fitted with doors which swing down and out to 'drop bottom'. The broken bricks are replaced and the bottom door is closed after removing residues of previous melting. Up to 200 mm height a sand bed is prepared with slope towards tap hole. A tap hole is pluged with clay. Slag hole is prepared finally to separate and remove slag. And now cupola is dried thoroughly.
Firing
Oil waste and wooden piece. Sufficient air is supplied when woods start burring coke is charged at several places. Again and again coke is charged to cupola at several portion. More coke is added up to tuyere level. Blast turned off and more coke is added and allowed to burn The coke is allowed to burn half an hour. Finally charging is done through charging doors.
Charging and Melting
Pig iron and iron scrap are charged in to furnace through charging door. Then coke is charged alternately. Lime stone is added to remove impurities and ensure through mixing of molten metal. The ratio between pig iron and limestone is 25:1 and ratio between pig iron to coke is 10:1. The cupola charged fully with this ratio and iron is socked for one hour. Blast is turned on now and molten metal is begin to collect at the sand bed. Melting required quantity the clay plug is removed and collected in ladle.
These molten metal poured in to moulds directly and the floating slag at top level is tapped out through the slag holes. Again furnace is to be cleaned and loaded for further melting. 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.
Cupola shut off
Stop the air blast. .Molten metal is removed. Bottom doors are open and waste are dropped down and quenched by water.
Advantages
1 Initial cost lower than other type furnace.
2. It is simple in design
3. It require only small floor area
4. Operation and maintenance are simple.
5.Can be operated for many hours continuously
.
Various type of furnaces used in Foundry. The selection of the furnace depends on the type of metal to be melt and the quantity of metal to be melt.
The metal melting furnace used are
1. Cupola furnace
2. Open hearth furnace
3. Crucible furnace (1.Pit type furnaces, 2. Coke fired stationary furnaces 3. Oil fired tilting furnaces )
4. Pot Furnace
5. Electric Furnace ( 1. Direct arc furnace , 2. Indirect arc furnace, 3. Induction furnace )
CUPOLA FURNACE
This furnace used for melting Cast Iron
A cupola or cupola furnace is a melting device used in foundries that can be used to melt cast iron, ni-resist iron and some bronzes. The cupola can be made almost any practical size. The size of a cupola is expressed in diameters and can range from 1.5 to 13 feet (0.5 to 4.0 m). The overall shape is cylindrical and the equipment is arranged vertically, usually supported by four legs. The overall look is similar to a large smokestack.
construction
Vertical cylindrical shell made out of 10mm thick steel plate. Inside is lined with refractory bricks . Two bottom door closes the Cupola furnace. Sand bed is laid over the bottom door. This sand bed slopes towards the tap hole. Molten metal stays over this bed. Concrete legs are set at the bottom of the Cupola furnace. Tape hole is provided to take out the molten metal. A plug made out of clay closes the tape hole. The slag floating over the molten metal is removed through this slag hole.
One meter above the bottom opening called tuyeres are provided to feed fuel for complete combustion of fuel. There is a wind box and blower to supply air for combustion. For charging fuel and metal a separate charging door is provided.
Preparation
Waste and slag of previous melting is cleaned using the bottom of the cylinder which is fitted with doors which swing down and out to 'drop bottom'. The broken bricks are replaced and the bottom door is closed after removing residues of previous melting. Up to 200 mm height a sand bed is prepared with slope towards tap hole. A tap hole is pluged with clay. Slag hole is prepared finally to separate and remove slag. And now cupola is dried thoroughly.
Firing
Oil waste and wooden piece. Sufficient air is supplied when woods start burring coke is charged at several places. Again and again coke is charged to cupola at several portion. More coke is added up to tuyere level. Blast turned off and more coke is added and allowed to burn The coke is allowed to burn half an hour. Finally charging is done through charging doors.
Charging and Melting
Pig iron and iron scrap are charged in to furnace through charging door. Then coke is charged alternately. Lime stone is added to remove impurities and ensure through mixing of molten metal. The ratio between pig iron and limestone is 25:1 and ratio between pig iron to coke is 10:1. The cupola charged fully with this ratio and iron is socked for one hour. Blast is turned on now and molten metal is begin to collect at the sand bed. Melting required quantity the clay plug is removed and collected in ladle.
These molten metal poured in to moulds directly and the floating slag at top level is tapped out through the slag holes. Again furnace is to be cleaned and loaded for further melting. 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.
Cupola shut off
Stop the air blast. .Molten metal is removed. Bottom doors are open and waste are dropped down and quenched by water.
Advantages
1 Initial cost lower than other type furnace.
2. It is simple in design
3. It require only small floor area
4. Operation and maintenance are simple.
5.Can be operated for many hours continuously
.