Forming Processes includes Rolling, Forming, Extrusion and Drawing processes with sub-types involved

1. METAL FORMING

2.  Forming process is a manufacturing process which
make use of suitable stresses which cause
deformation of metals to produce required shapes.
 During forming process no material is removed , i.e.
they are deformed and displaced.

3. Hot Working:
 Hot working is the deformation that is carried out above
the re-crystallisation temperature.
 In this the mechanical properties remains unchanged.
 Less energy required than cold working.
Cold Working:
 The process is performed at room temperature ,but mildly
elevated temperatures may be used to provide increased
ductility and reduced strength.
 Better control of dimensions and good surface finishing.

4.  Metal forming process can be classified under two
groups. Bulk deformation and Sheet metal process.
 Bulk deformation is that the work formed as a low
surface area to volume ratio.
 The following is a brief view of bulk deformation
process.
 Bulk deformation is of three types :
1. Rolling process
2. Extrusion process
3. Drawing process.

5.  Rolling is a metal forming process that deforms the
material by using rollers without change in volume.
 Rolling process include flat rolling, shape rolling,
ring rolling, thread rolling etc.

6. Grain Structure :
 Rolling a metal above recrystallization temperature
breaks the old grain structure and reforms a new one
along with uniform grain structure.
 Metal rolling pushes material closing up vacancies
and cavities within the metal.

7. Two End High Rolling Mill:
 It consists of two rolls located one above the other with their
centres in vertical plane .A controlled opening or gap is
provided between the rolls. They are driven by motor and
rotate in opposite directions.
 The rolling direction can be changed by changing the direction
of rotation of the rolls.

8.  Three End High Mill:
 This machine consists of three rolls
located one above the other with
their centres in a vertical plane.
 Outer rolls will be rotating in one
direction and the centre one will
rotate in opposite direction.
 In this the rolling takes place in
both the directions
 Four End High Mill:
 Here four rolls are used.
 Two smaller forms the main rolls
and come in contact with work
piece and cause deformation.
 Thus the mill is more rigid and
used for higher reduction in work

9.  Cluster Mill:
 Here the main rolls are
small and backed up by two
sets of rolls on each side.
 Higher rigidity and stability
is imparted to the mill.
 Better deformation will take
place
 Tandem Mill:
 A series of four high mills
are used one after the other.
 The work piece is passes
through each one of them.
Reduction in the thickness
will takes place at each
point.
 This arrangement is called
Tandem Mill.

10.  It is a metal forming process in which a work piece of length
and cross section is forced to flow through die of smaller c/s
area thus forming work to new cross section.
 Extrusion is of five types:
1.Direct process.
2.Indirect process.
3.Impact process.
4.Hydro static process.
5.Tube process.

11.  Direct Extrusion:
 It is a similar better process
in which ram exerts a force
on one side of work piece
through which the material
is extruded on opposite side
of chamber .
 The metal flows in same
direction that the force is
applied.
 Indirect Extrusion:
 It is a particular type
process in which the work
piece is located in the
chamber that is completely
closed at one side
 The ram exerts a force on
one side of work piece in
which metal flows in the
opposite direction that the
force is applied.

12.  Impact Extrusion:
 It is a type of cold forming
used for hollow cores and
thin wall thickness
 A punch driven into a die by
the force of press causes the
metal blank to flow in
forward and backward
manner.

 Hydro Static Extrusion:
 In this process the container is
filled with a fluid which
transmits pressure to the billet
which then extruded through a
die. No friction acts along the
walls of container.
 Due to pressurised fluid
lubrication is very efficient
and produces good surface
finish.

13.  Tube Extrusion:
 It makes use of mandrel to
shape the inside of tube. Hot
billet is placed in the
container and the die
containing mandrel is
forced through billet. The
ram moves forward and
extrudes the metal through
the die

14.  Drawing is a cold working process in which the work piece is
pulled through a tapered hole in a die so as to reduce its
diameter.
 It increases strength and hardness of the metal.
 There are two types of drawing process.
1. Wire Drawing
2. Tube Drawing.
 Wire Drawing:
 It is a process in which the cross section of the wire is reduced
by pulling it through a die.
 Die angle has greater influence on the drawing force and the
quality of the drawn product.

15.  Tube Drawing:
 Tube drawing is very similar to bar drawing except the
beginning stock is a tube. It is used to decrease the
diameter, improve surface finish and improve
dimensional accuracy.
 A mandrel may or may not be used depending on the
specific process used.

16. Advantages:
 Better surface finish is obtained.
 Strength, fatigue and wear properties are improved through
strain hardening.
 Products possess better reproducability.
Disadvantages:
 Higher forces required to initiate and complete the
deformation.
 Less ductility is available.
 Heavier and most powerful equipment is required.

17. Defects of Metal Forming:
 Surface crack:
 Excessive working at low temperature.
 High sulphur concentration.
 Formation of rust.
 Internal cracks:
 By applying uneven tensile stresses/forces.
 Alligatory:
 Defects in the original cast material.
 The surface is divided into two materials.
 Lubrication Residue