This document discusses different types of furnaces used for melting metals. It begins by outlining factors to consider when selecting a furnace, such as initial cost, fuel cost, metal properties, and production needs. It then classifies furnaces according to the metal they melt - for gray cast iron, steel, and non-ferrous metals. Specific furnace types are listed for each metal. The document focuses on cupola furnaces next, describing their widespread use for iron melting and characteristics like their water-cooled cylindrical design lined with refractory material. Construction details of cupola furnaces are provided.
Selection of furnaces and various types of furnaces (UNIT2)
1. Selection of Furnaces and
various types of Furnaces
Prepared by
Ankit saxena
Assistant Professor
ADGITM, NEW DELHI
2. Selection of melting furnaces
The selection of a foundry furnace depends upon the
following factors:
i. Initial cost of the furnace
ii. Fuel cost
iii. Kind of metal or alloy to be melted
iv. Melting and pouring temperature of the metal to be cast
v. Quantity of metal to be melted
vi. Cost of furnace repair and maintenance
vii. Cost of melting per unit weight of the metal
viii. Chances of metal to absorb impurities during melting
ix. Quantity of the finished product desired
3. Furnaces can also be classified according to the molten metal
1. Gray Cast Iron
i. Cupola
ii. Air furnace
iii. Rotary furnace
iv. Electric arc
furnace
2. Steel
i. Open hearth furnace.
ii. Electric furnace.
Arc furnace
High frequency induction furnace
3. Non-ferrous metals
i. Crucible furnaces (Al ,Cu)
Pit type
Tilting type
Non-tilting or bale out type
Electric resistance type (CU)
ii. Pot furnaces (fuel fired) (Mg & Al)
Stationary
Tilting
iii. Reverberatory furnaces (fuel fired ) (Al & Cu)
Stationary
Tilting
iv. Rotary furnaces
Fuel fired
Electrically heated
v. Induction furnaces (Al & Cu)
Low frequency
High frequency
vi. Electric Arc furnaces (Cu)
4. CUPOLA FURNACE
i. For many years, the cupola was the primary method of
melting used in iron foundries.
ii. The cupola furnace has several unique characteristics which
are responsible for its widespread use as a melting unit for
cast iron.
iii. Cupola furnace is employed for melting scrap metal or pig
iron for production of various cast irons. It is also used for
production of nodular and malleable cast iron. It is available
in good varying sizes. The main considerations in selection of
cupolas are melting capacity, diameter of shell without lining
or with lining, spark arrester.
Shape
A typical cupola melting furnace consists of a water-cooled
vertical cylinder which is lined with refractory material.
5. i. Construction
ii. The construction of a conventional
cupola consists of a vertical steel
shell which is lined with a refractory
brick.
iii. The charge is introduced into the
furnace body by means of an
opening approximately half way up
the vertical shaft.
iv. The charge consists of alternate
layers of the metal to be melted,
coke fuel and limestone flux.
v. The fuel is burnt in air which is
introduced through tuyeres
positioned above the hearth. The
hot gases generated in the lower
part of the shaft ascend and preheat
the descending charge.