CHARACTERISTICS OF COLD WORKING

CHARACTERISTICS OF COLD
WORKING

The main characteristics of cold working
are given as under.


1. Cold working involves plastic
deformation of a metal, which results in strain hardening.

2. It usually involves working at ordinary (room) temperatures, but, for
high melting point metals, e.g., tungsten, the cold working
may be carried out at a red heat.

3. The stress
required
for deformation increases
rapidly with
the amount of deformation.

4. The amount of deformation, which can
be performed without introducing other treatment, is limited.

5. Cold
rolling process generally distorts grain structure.

6. Good
surface finish is obtained in cold rolling.

7. The upper temperature limit for cold
working is the maximum temperature at which strain hardening is retained. Since
cold working takes place below the recrystallisation temperature, it produces
strain hardening.

8. Excessive cold working gives rise to
the formation and propagation of cracks in the
metal.

9. The
loss of ductility during cold working
has a useful side effect
in machining.

10. With less
ductility, the chips break more
readily and facilitate the cutting operation.

11. Heating is sometimes required.

12. Directional properties can be easily imparted.

13. Spring back is a common phenomenon present in cold-working processes.

For relatively ductile metals, cold
working
is often more economical
than
hot working.

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