Introduction to Basic Manufacturing Processes and ... - always yours

Melting Furnaces 103
2. Steel
(a) Electric furnaces
(b) Open hearth furnace
3. Non-ferrous Metals
(a)
(b)
(c)
(d)
(e)
(f)
Reverberatory furnaces (fuel fired) (Al, Cu)
(i)
(ii)
Stationary
Tilting
Rotary furnaces
(i)
(ii)
Fuel fired
Electrically heated
Induction furnaces (Cu, Al)
(i)
(ii)
Low frequency
High frequency.
Electric Arc furnaces (Cu)
Crucible furnaces (AI, Cu)
(i)
(ii)
Pit type
Tilting type
(iii) Non-tilting or bale-out type
(iv)
Electric resistance type (Cu)
Pot furnaces (fuel fired) (Mg and AI)
(i)
(ii)
Stationary
Tilting
Some of the commonly used furnaces in foundries are discussed as under.
6.3 BLAST FURNACE
After mining, various kinds of iron ores are brought to the blast furnace which is the starting
process for refining iron ores or mined ores and for the poduction of pig iron. Blast furnace
was invented in 14th century. A typical blast furnace along with its various parts is shown
in Fig. 6.1. It is large steel shell about 9 mt. in diameter which is lined with heat resistant
bricks. It is set on the top of brick foundation. There are four major parts of blast furnace
from bottom to top hearth, bosh, stack and top. The hearth acts as a storage region for
molten metal and molten slag. The charge of blast furnace possesses successive layers of iron
ore, scrap, coke, and limestone and some steel scrap which is fed from the top of the furnace.
Iron ore exists as an aggregate of iron-bearing minerals. These mineral aggregates are oxides
of iron called hematite, limonite, and magnetite. They all contribute to the smelting process.
Hematite is a red ore and contains about 70% iron. Limonite is a hydrated oxide and contains
about 60% iron. Magnetite is a magnetic oxide and contains about 72% iron. It takes about
1.6 tons of iron ore, 0.65 ton of coke, 0.2 ton of lime-stone and about 0.05 ton of scrap iron
and steel to produce 1 ton of pig iron. For burning this charge, about 4 tons of air is required.
The impurities or other minerals are present in the ore. These impurities may be silicon,