CRUCIBLE FURNACE

Crucible furnace is for the melting of non ferrous metals.

Its capacity may range from 30 to 150 kg.

The types of crucible furnace are:

1) Pit furnace

2) Coke fired stationery furnace

3) Oil fired tilting furnace

4) Pot furnace

1) PIT FURNACE

The crucible is placed in a pit below the floor

level, it is fired with coke.

The charge to be melted is placed in crucible;

coke is packed around the crucible. Natural

draft is provided by a tall chimney.

Many crucibles can be placed in a single pit.

After the metal is melted, the covers are

removed, the crucibles are lift out with the

help of tongs and taken to pouring placed.

This furnace is used for melting non ferrous

metals.

2) COKE FIRED STATIONERY FURNACE

This furnace is used for melting non ferrous

metals in small quantity.

This furnace is placed above the floor level.

The crucible is placed in the heating chamber.

The heating chamber is lined with refractories.

Coke is used as fuel. Forced draft is used.

A blower is used for supply of air.

3) OIL FIRED TILTING FURNACE

This furnace is used for melting non ferrous metals in small

quantity and is fired by oil.

This furnace is mounted on two pedestals above the floor level.

For pouring the molten metal, the furnace is rotated by the

geared hand wheel.

Oil and air are admitted with pressure through a nozzle.

The crucible is placed in the heating chamber and is heated by

the flame.

The furnace can be stopped whenever needed & temperature

can be controlled easily.

They give lesser pollution.

4) POT FURNACE

Pot furnace is used for melting non ferrous

metals like aluminum, magnesium, tin, lead etc.

The pot is made up of cast iron or steel.

The furnace may be fired by gasoline oil or

coke.

The molten metal is taken out of the pot furnace

by using ladles.

Normally the capacity of pot furnace is around

500 kg.

ELECTRICAL RESISTANT HEATING FURNACE

In resistance heating furnaces, the resistance heating elements are used to generate the

heat in a heating chamber.

The electrical resistance of an electrical element measures its opposition to the passage

of an electric current.

A heating element converts electricity into heat through the process of Joule heating.

Electric current through the element encounters resistance, resulting in heating of the

element.

The heating elements used are Nichrome wire (80% nickel, 20% chromium), Kanthal

wire (Kanthal is the trademark for a family of iron-chromium-aluminium (FeCrAl)

alloys) or Graphite rods depending upon the temperature requirements.

Metal charge is placed in a crucible or pot which is indirectly heated by heating

elements.

The temperature is controlled using thermostats and the temperature is monitored by

thermocouples.

The heating chamber is constructed by M.S. Sheets and channels and for thermal

Insulation, fire clay bricks and refractory bricks are used.