2. FORMING
1. Forming, or metal forming, is the manufacturing process in which met
als are given the required shape through mechanical deformation.
2. the physical shape of a material is permanently deformed.
3. the workpiece is reshaped without adding or removing material, and its
mass remains unchanged.
4. The force applied for deformation should be more than the elastic limit
but less than the ultimate yield strength of the metal.
5. Brittle material cannot be formed.
3. ADVANTAGES
1. The amount of wastage of metal during metal forming p
rocess is negligible.
2. Grain orientation is possible.
3. Because of grain orientation the material is converted fr
om isotropic to anisotropic material.
4. Sometimes the strength and hardness of work material i
s increasing.
5. Some other metal forming process, the surface finish ob
tained on the component is very good and excellent.
4. 1. Higher amount of force and energy is required for
metal forming process compared to other
manufacturing methods.
2. Except the forging operation, all other metal
forming process are used for producing uniform
cross sectioned components only.
3. The components with cross holes cannot be
produced easily using metal forming process.
DISADVANTAGES
5. Re-crystallization
Recrystallization –
Recrystallization is a process by which deformed grains are replaced by a new
set of defects-free grains that nucleate and grow until the original grains have be
en entirely consumed.
Recrystallization is usually accompanied by a reduction in the strength and hard
ness of a material and a simultaneous increase in the ductility.
Recrystallization temperature-
The temperature at which 50%of the cold worked material will recrystallize in o
ne hour.
6. Classification of forming
Forming can be classified in two different
categories-
Hot forming or hot-working –
Plastic deformation above the recrystallization temperature but
below the melting point is called hot forming.
cold forming or cold-working –
Plastic deformation below the recrystallization temperature is
called cold forming.
7. Hot Working Cold Working
Advantages --
1. Force requirement is less
2. Refined grain structure
3. No stress formation
4. Quick and Economical
5. Suitable for all metals
Disadvantages --
1. Poor surface finish
2. Less accuracy
3. Close tolerances cannot be
achieved
4. Sheets and wires cannot be
produced
Advantages --
1. Better surface finish
2. High dimensional accuracy
3. Sheets and wires can be
produced
4. Suitable for Mass production
Disadvantages--
1. Stress formation in metal
very high .
2. Very high tooling and
handling cost
3. Strain hardening occurs
8. Methods of hot working
Rolling-
decrease thickness and increase the
lengh of metal
Forging-
the working of metal by localized
compressive forces.
Piercing –
used to create cavity or hole in the work
piece.
Drawing-
making hollow cup type out of flat
metallic sheet.
Spinning-
a disc or tube of metal is rotated at
high speed and formed into an
axially symmetric part
Extrusion-
the metal confined to a pressure
chamber and is forced out through a
formed die of required shape.
9. Methods of cold working
1. Rolling
2. Forging
3. Drawing
4. Bending
5. Spinning
6. Extrusion
7. Squeezing
8. Peening
9. Sizing
10. Coining
11. Hobbing
12. Embossing
