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2. ELECTRIC FURNACES

3. 3
ELECTRIC FURNACES
 Employed for the production of high quality castings, because
the furnace atmosphere can be more closely controlled, losses
by oxidation can be eliminated, alloying elements can be added
without fear of loss
 Composition of the melt and its temperature can be accurately
controlled
 Capacity of electric furnaces ranges from 250 kg to 10 tons
Types of electric furnaces:
 Direct arc furnace
 Indirect arc furnace
 Core type induction furnace

4. 4
DIRECT ARC FURNACES

5. 5
DIRECT ARC FURNACES
 Interior of the furnace is preheated
 Preheated is done by alternatively striking and breaking the arc
between the electrodes and used electrode pieces kept on the
hearth
 Electric arc is drawn between the electrodes and metal charge
 Temperature – 6094 °c
 Slag form due to melting of flux, sand etc.,
 Slag is removed by tilted the furnace backward
 Molten metal taken out by tilted the furnace forward

6. 6
DIRECT ARC FURNACES
ADVANTAGES
 Undertake a definite metal refining sequence
 Analysis of melt can be kept to accurate limits
 High thermal efficiency as high as about 70%
 Preferred for its quicker readiness for use
DISADVANTAGE
 Heating cost are higher

7. 7
INDIRECT ARC FURNACES

8. 8
INDIRECT ARC FURNACES
ADVANTAGES
 The furnace is charged with pig iron and scrap is placed above
 When the electric power is ON, graphite electrodes are brought
nearer till the current jumps and an electric arc is set up between them
 The heat generated in the arc is responsible for melting the charge
DISADVANTAGES
 Initial cost and its auxiliary equipment is high
 Time available for analyzing the melt composition is very small

9. SPECIAL MOULDING
PROCESSES