Introduction Hot Working and Cold Working of Metals Forging Processes- Open, impression die forging, Closed die forging-forging operation Rolling of metals-types of rolling- Flat strip rolling-shape rolling operation -Defects in rolled parts- Principle of rod and wire drawing-tube drawing -Principle of extrusion Types-hot and cold extrusion.

1. RAMCO INSTITUTE OF TECHNOLOGY
Mr.M.LAKSHMANAN
Assistant Professor (Senior Grade)
Department of Mechanical Engineering

2. UNIT-III
Metal Forming Processes

3. Unit III - Syllabus
Introduction Hot Working and Cold Working of
Metals Forging Processes- Open, impression
die forging, Closed die forging-forging
operation Rolling of metals-types of rolling-
Flat strip rolling-shape rolling operation -
Defects in rolled parts- Principle of rod and
wire drawing-tube drawing -Principle of
extrusion Types-hot and cold extrusion.

4. Forming/Metal Forming
Forming or metal forming, is
the metalworking process of fashioning metal
parts and objects through mechanical
deformation; the workpiece is reshaped
without adding or removing material, and its
mass remains unchanged.
Forming operates on the materials
science principle of plastic deformation,
where the physical shape of a material is
permanently deformed.

5. Metal forming processes are:
Forging
Rolling
Extrusion
Drawing
Pressing
Metal forming can be done by Three types:
1. Hot working
2. Warm working
3. Cold working

6. Hot working
It is defined as the plastic deformation of metal
above their recrystallization temperature but
below the melting point.
The new crystals are to start forming when the
atoms of metal reach a certain higher energy
level under the action of heat and force. This is
called Re-crystallization.
This is important because recrystallization
keeps the materials from strain hardening,
which ultimately keeps the yield strength,
hardness and high ductility.

7. Advantages:
• The process is quick and economical.
• Deformation occurs in less forces.
• Mechanical properties such as ductility,
elongation, toughness can be improved.
• This process is suitable for nearly all the
commercial metals.
• The blow holes, cracks are eliminated.

8. Disadvantages:
• The cost of the tooling and handling are
very high.
• Poor surface finish.
• The close tolerances can not be achieved.
• Life of the equipment is less.
• Skilled labour is required to maintain the
hot metals.

9. Warm working
The material deformation carried between hot
and cold working is called Warm working.
Warm Forming is the process of deforming metal
heated to a temperature that maximizes the
material’s malleability without allowing re-
crystallization, grain growth, or metallurgical
fracture.
Temperatures can range from 200-850 degrees C.

10. Advantages
• The equipment works under lighter loads.
• Metal ductility is more.
• Less strain hardening
• Less amount of heat energy is required.
• Good precision is achieved.
• Good surface finish.

11. Cold working
It is defined as the plastic deformation of
metal below their recrystallization
temperature at room temperature. (or
above room temperature).

12. Advantages
• No heating is required.
• Strength, fatigue and wear properties are
improved.
• Better surface finish is obtained.
Disadvantages
• Higher forces are required.
• Less ductility is available.
• More powerful equipment is required.
• Metal surfaces must be clean and scale-free.

13. Recrystallization
Recrystallization temperature is the temperature
at which the first new grains appears. It requires
realignment or diffusion in a materials.
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 been entirely consumed.
Recrystallization is usually accompanied by a
reduction in the strength and hardness of a
material and a simultaneous increase in
the ductility.

14. Recrystallization of a metallic material (a → b) and
crystal grains growth (b → c → d).

15. Strain Hardening
Work hardening, also known as strain
hardening is the strengthening of a metal
by plastic deformation.
This strengthening occurs because
of dislocation movements and dislocation
generation within the crystal structure of
the material.

16. Comparison between hot and cold working processes
SI.No Hot working Cold working
1. Processing done at temperature
above recrystallization
temperature.
Processing done at temperature
below recrystallization
temperature
2. Forces required are lower Forces required are higher
3. New crystals are formed due to
recrystallization
Recrystallization does not occur
4. Blow holes, porosity and cracks
are eliminated due to by the high
working pressure.
Excessive cold working can lead to
production and propagation of
cracks
5. Difficulty in handling; require heat
resistant tools
No such requirement
6 Dimensional accuracy is poor Dimensional accuracy is much
better
7 Oxidation and scaling result in
poor appearance.
Finish obtained is much better
8. Thin gauge sheet and fine wires
cannot be produced.
Even very thin sheets and fine
wires can be produced.

17. Classification of mechanical working of metals
Mechanical working of metals
Hot working Cold working
• Forging
• Rolling
• Extrusion
• Spinning
• Drawing
• Tube Piercing
• Drawing
• Coining
• Sizing
• Extrusion
• Squeezing
• Bending
• Shearing

18. Hot-working operation
• Forging
– Open die forging
– Closed die forging
– Impression die forging
• Rolling
• Extrusion
• Spinning
• Drawing
• Tube Piercing

19. Forging
Forging is a manufacturing process involving
the shaping of metal using
localized compressive forces. The blows are
delivered with a hammer (often a power
hammer) or a die.
Forging is often classified according to the
temperature at which it is performed:
• Cold forging (a type of cold working),
• Warm forging, or hot forging (a type of hot
working).

20. Forging is a deformation processing of materials
through compressive stress. It is carried out either
hot or cold.
Hot forging is done at temperatures above
recrystallization temperatures, (0.6 Tm, or above)
Where,
Tm is melting temperature.
Warm forging is done in the temperature range: 0.3
Tm to 0.5 Tm.
Cold forging has advantages such as good surface
finish, high strength and greater accuracy.

21. Applications:
bolts, disks, gears, turbine disk, crank shaft,
connecting rod, valve bodies, small components
for hydraulic circuits etc.
Advantages:
• Closer dimensional accuracies achieved
require very little machining after forging.
• Material saving is the result.
• Higher strength, greater productivity, favorable
grain orientation, high degree of surface finish
are other merits.

22. Forging
Forging is a process in which the work piece is
shaped by compressive forces applied
through various dies and tools.
Forging Process
• Open die forging
• Closed die forging
• Impression die forging

23. Forging Tools
• Tongs
• Hot chisel
• Round punch
• Cold chisel
• Anvil
• Hammer

24. Forging Tools

25. Open die forging
Open die forging is the process of deforming a
piece of metal between multiple dies that do
not completely enclose the material.
The metal is altered as the dies “hammer” or
“stamp” the material through a series of
movements until the desired shape is
achieved.

26. Open die forging

27. Open-die forging is a hot forging process in
which metal is shaped by hammering or
pressing between flat or simple contoured
dies
• Equipment: Hydraulic presses, hammers.
• Materials: Carbon and alloy steels,
aluminium alloys, copper alloys, titanium
alloys, all forgeable materials.

28. Closed Die Forging

29. Closed die forging process, a billet is formed (hot)
in dies (usually with two halves) such that the
flow of metal from the die cavity is restricted.
The excess material is extruded through a
restrictive narrow gap and appears as flash
around the forging at the die parting line.
• Equipment: Anvil and counterblow hammers,
hydraulic, mechanical, and screw presses.
• Materials: Carbon and alloy steels, aluminium
alloys, copper alloys, magnesium alloys,
beryllium, stainless steels, nickel alloys, titanium
and titanium alloys, iron and nickel and cobalt
super alloys.

30. Closed Die Forging is a forging process in which dies
move towards each other and covers the workpiece
in whole or in part.
The heated raw material, which is approximately the
shape or size of the final forged part, is placed in the
bottom die.
The shape of the forging is incorporated in the top
or bottom die as a negative image. Coming from
above, the impact of the top die on the raw material
forms it into the required forged form

31. Impression Die-Forging

32. • In impression-die forging the heated work
piece is placed between two required
shaped die and is pressed or hammered.
• During hammering or pressuring it takes
the shape of the die.
• A small amount of materials is forced
outside the die impression, which is finally
trimmed.

34. Comparison of open-Die and closed Die forging
Open Die Forging Closed Die Forging
Open-die forging is a hot forging
process in which metal is shaped by
hammering or pressing between flat
or simple contoured dies.
In this process, a billet is formed (hot)
in dies (usually with two halves) such
that the flow of metal from the die
cavity is restricted
It is a small mass production It is a heavy mass production
low production efficiency High production efficiency
high labour intensity Low labour intensity
Equipment: Hydraulic presses,
hammers.
Equipment: Anvil and counterblow
hammers, hydraulic.
Materials: Carbon and alloy steels,
aluminium alloys
Materials. Carbon and alloy steels,
copper alloys, magnesium alloys,
stainless steels
Application: Forging ingots, large and
bulky forgings
Application: automobiles, trucks,
tractors, off-highway equipment,
aircraft, railroad

35. Upsetting
Upset forging increases the diameter of the
work piece by compressing its length. A few
examples of common parts produced using the
upset forging process are engine valves,
couplings, bolts, screws, and other fasteners.

37. Roll Die forging

38. Roll Die Forging
Roll forging is a process where round or flat bar
stock is reduced in thickness and increased in length.
Roll forging is performed using two cylindrical or
semi-cylindrical rolls, each containing one or more
shaped grooves.
A heated bar is inserted into the rolls and when it
hits a stop the rolls rotate and the bar is
progressively shaped as it is rolled through the
machine.

40. Drop forging

41. Drop forging
Drop forging is a forging process where a
hammer is raised and then "dropped" onto the
work piece to deform it according to the shape
of the die.

42. Hot spinning

43. Hot spinning
It is a metalworking process by which a disc
or tube of metal is rotated at high speed and
formed into an axially symmetric art.
Spinning can be performed by hand or by a
CNC lathe.

45. Piercing

46. Piercing
• It can be used to create a cavity or hole in the work
piece.
• Piercing is a shearing process where a punch and die
are used to create a hole in sheet metal or a plate.
• Blanking and piercing are shearing processes in which
a punch and die are used to modify webs. The tooling
and processes are the same between the two, only the
terminology is different:
• In blanking the punched out piece is used and called
a blank;
• In piercing the punched out piece is scrap. The process
for parts manufactured simultaneously with both
techniques is often termed "pierce and blank." An
alternative name of piercing is punching.

48. Ring Rolling

49. Ring rolling is a particular category of
metal rolling, in which a ring of smaller
diameter is rolled into a precise ring of larger
diameter and a reduced cross section. This is
accomplished by the use of two rollers, one
driven and one idle, acting on either side of
the ring's cross section.

50. The work will essentially retain the same volume,
therefore the geometric reduction in thickness will be
compensated for entirely by an increase in the ring's
diameter.

51. Skew Rolling

52. Skew rolling is a metal forging process that uses
two specially designed opposing rolls, that rotate
continuously.
Round stock is fed into the rolls, the material is
forged by each of the grooves in the rolls and
emerges from the end as a metal ball.
The stock is fed through the rolls continuously,
but each ball is produced separately, thus it is a
discrete process and not a continuous one.
Skew rolling, similar to roll forging, is a
manufacturing process that bears qualities of
both metal rolling and metal forging.

54. Hydraulic Presses

55. Hydraulic Presses
The hydraulic press depends on Pascal's principle:
the pressure throughout a closed system is
constant.
One part of the system is a piston acting as a pump,
with a modest mechanical force acting on a small
cross-sectional area; the other part is a piston with
a larger area which generates a correspondingly
large mechanical force.
Only small-diameter tubing (which more easily
resists pressure) is needed if the pump is separated
from the press cylinder.

57. Pneumatic Power Hammer

59. Pneumatic Power Hammer
Power hammer consists of a frame, an anvil, and a
reciprocating ram holding a hammer head or die. The
work piece is placed on the lower anvil or die and the
head or upper die strikes the work piece.
The power hammer is a direct descendant of the trip
hammer, differing in that the power hammer stores
potential energy in an arrangement of mechanical
linkages and springs, in compressed air and by the fact
that it accelerates the ram on the downward stroke.
This provides more force than simply allowing the
weight to fall.

60. Pneumatic Power Hammer

61. Ironing
• Ironing is the process of smoothing and
thinning the wall of a shell or cup (cold or
hot) by forcing the shell through a die with a
punch.
• Equipment: Mechanical presses and
hydraulic presses.
• Materials: Carbon and alloy steels,
aluminium and aluminium alloys, titanium
alloys.
• Applications: Shells and cups for various
Machines.

62. Ironing
Ironing is carried out by pulling the workpiece
through an ironing ring with the help of a punch. The
wall thickness of the hollow body is reduced in this
process.

63. Swaging
Process that reduces/increases the diameter,
tapers, rods or points round bars or tubes
by external hammering.

64. Swaging is a forging process in which the
dimensions of an item are altered using dies
into which the item is forced.

66. Cold-working operation
• Bending
• Shearing
• Drawing
• Presses
• Rolling
• Cold Forging
• Thread Rolling
• Coining

67. ROLLING
Process used in sheets, strips, bars, and rods
to obtain products that have smooth
surfaces and accurate dimensions.

68. Rolling is a metal forming process in
which metal stock is passed through one or
more pairs of rolls to reduce the thickness
and to make the thickness uniform.

69. Cold Forging
Cold forging deforms metal while it is below
its recrystallization point. Cold forging is
generally preferred when the metal is
already a soft metal, like aluminum.
This process is usually less expensive than hot
forging and the end product requires little, if
any, finishing work.

70. Cold Forging
Process in which slugs of material are
squeezed into shaped die cavities to
produce finished parts of precise shape and
size.

72. Thread rolling
Thread rolling is a metal rolling process used
extensively in manufacturing industry to
produce screws, bolts and other fasteners.
A common thread rolling process, used in
industry to manufacture threaded parts,
involves forming the threads into the metal
of a blank by a pressing and rolling action
between two die.
The die surfaces hold the shape and the force
of the action forms the threads into the
material.

73. Thread rolling
Process is used for making external threads;
in this process, a die, which is a hardened
tool with the thread profile, is pressed on to
a rotating work piece.

74. Thread Rolling

75. Bending

76. Bending
Bending is a manufacturing process that
produces a V-shape, U-shape, or channel
shape along a straight axis in ductile
materials, most commonly sheet metal.
Commonly used equipment include box and
pan brakes, brake presses, and other
specialized machine presses.

78. Shearing

79. Shearing
Shearing, also known as die cutting, is a
process which cuts stock without the
formation of chips or the use of burning or
melting. Strictly speaking, if the cutting
blades are straight the process is called
shearing; if the cutting blades are curved
then they are shearing-type operations.
The most commonly sheared materials are in
the form of sheet metal or plates, however
rods can also be sheared.

81. Coining
Coining is a closed die forging process, in
which pressure is applied on the surface of the
forging in order to obtain closer tolerances,
smoother surfaces and eliminate draft.
Closed die forging is a process in which
forging is done by placing the work piece
between two shaped dies.
This process may be done in hot or cold
working conditions, but is predominantly a
cold work process.

82. Coining

83. Coining
coining is used to form indentations and
raised sections in the Part. During the process,
metal is intentionally thinned or thickened to
achieve the required indentations or raised
sections.

85. Advantages of Coining
• Produces finer and detailed surface finish
• Provides accurate bends in a consistent
manner
• Does not require expensive machinery
• The work hardened surface can resist impact
and abrasion
• Eliminates the need for complex finishing
processes
• Plastic flow reduces the surface grain size and
work hardens the surface.

86. Industrial Applications
• Minting of coins and medallions
• Making of jewelry
• Making badges, buttons, precision-energy
springs
• Making complex electronic parts
• Making precision parts that require finer
polished surface finishes.

88. Drawing
Drawing is a metalworking process which
uses tensile forces to stretch metal. As the
metal is drawn (pulled), it stretches thinner,
into a desired shape and thickness.
It is broken up into two types:
• Sheet metal drawing
• Wire, bar, and tube drawing.

91. Press forging
Press forging works by slowly applying a
continuous pressure or force, which differs
from the near-instantaneous impact of drop-
hammer forging.
The amount of time the dies are in contact
with the work piece is measured in seconds
(as compared to the milliseconds of drop-
hammer forges).
The press forging operation can be done
either cold or hot.

94. Press forging

96. Forging Defects

99. ROLLING
Process used in sheets, strips, bars, and rods
to obtain products that have smooth surfaces
and accurate dimensions. The metal is
subjected to high compressive stresses as a
result of the friction between the rolls and the
metal surface.

100. ROLLING
Rolling process is most common industrial process
used for making large length cross section like
sheets and plates of steel and aluminum for
structure and other works.
Rolling mills are used to perform rolling process.
These machines are available in different shapes
and size according to requirement of the process
and due to technical issues.
Every rolling mill consist minimum two rolls. These
numbers can extend according to the process
requirement.

102. Types of Rolling Mill

103. Types of rolling mills
• Two High Rolling Mill
• Three High Rolling Mill
• Four High Rolling Mill
• Tandem Rolling Mill
• Cluster Rolling Mill
• Planetary Rolling Mill

104. Two High Rolling Mill
This mill consist two rollers arranged as
shown in figure. Both the rollers rotate in
opposite direction for desire movement of
work piece. Work piece is feed between the
rollers which apply a compressive force and
tends to plastically deform work piece and
convert it into desire shape.

106. This machine can further classified
into two types
The first one is two high Non reversible
machine in which the rollers can rotate in only
one direction (Either clockwise or
anticlockwise) and thus work piece can feed
only in one direction (Either left to right or
right to left). One big problem arises in this
machine is that every time the work piece
carried back over the front side of mill to feed
again for reduction in thickness.

108. The other one is two high reversible machine
in which both the rollers can be rotate in both
directions. In this machine no need to carry
work piece at front side. We have to just
change the direction of rotation of rollers to
again pass the work piece through rollers for
decrease thickness.

109. Three High Rolling Mill
This type of rolling mill consist three rollers
arrange parallel to each other. In this machine
the middle roller rotate in opposite direction
of other two rollers. This machine is used to
reduce two times thickness in one pass. In this
machine, the work piece is feed between
bottom and middle roller in one direction and
top and middle rollers in opposite direction.
This machine can handle two work pieces in
single run.

112. Four High Rolling Mill
These machine consist four rollers (two small
and two big). These rollers are arranged as
shown in figure. Small rollers are in direct
contact with work piece and rotate in opposite
direction. Big rollers works as backup rolls and
they also rotates in opposite direction with each
other and also with contact roller. This machine
is used for cold rolling where high rigidity
required.

115. Tandem Rolling Mill
Tandem rolling is also known as continuous
rolling in which two or more set of four high
rolling mill arranged in a series in which each
set is called stand. These stands are arranged so
they can roll the work piece in decreasing cross
section. It is used for rolling thick work piece in
single pass.

118. Cluster Rolling Mill
In this type of rolling mill, each of working
roller is backup by two or more of larger
backup roller. These rollers are arrange as
shown in figure. This machine is used for
rolling hard material.

120. Planetary Rolling Mill
In this type of rolling machine, a large backup
roller is surrounded by various numbers of
planetary working rollers as shown in figure.
Each planetary roll gives constant reduction.
It is used to reduce large thickness in single
pass of steel strip. Its rolling capacity is more
than cluster machine but less than tandem
rolling machine.

122. The initial breakdown of ingots into blooms &
billets is generally done by hot-rolling. And
then cold-rolling is to be done to get good
surface finish and close control over
dimension.
HOT ROLLING: occurs above the
recrystallization temperature of the material

123. • Hot rolling is used mainly to produce sheet
metal or simple cross sections, such as rail
tracks.
• It will reduce the average grain size of metal,
this improves the strength of material.

124. COLD ROLLING
• Used to produce sheet & strip with superior
surface finish and dimensional tolerance.
• Also, the strain hardening results from the cold
reduction may be used to give increased strength.
• Total reduction achieved will vary from 50 to 90
percent.
• The lowest %age reduction is taken in the last
pass to permit better control of flatness, gage and
surface finish.
• Done usually at room temperature.

125. • Four-high or cluster mills are used. (Al, Cu alloys)
• Cold rolling cannot reduce the thickness of a
workpiece as much as hot rolling in a single pass.
• This process increases strength upto 20% via strain
hardening.

126. Hmax = μ2R
Hmax - Maximum thickness reduction in one pass
μ – Static friction coefficient between rolls and metal
R – Radius of rolls

127. HOT ROLLING
1. Blowholes and porosity
eliminates by welding
together.
2. This will results into
better ductility and
toughness.
3. Surface decarburization
of steels.
4. Not good surface finish.
5. Dimensional tolerance
due to expansion/
contraction of metal.
COLD ROLLING
1. Results in increased
strength or hardness.
2. Better dimensional control.
3. Good surface finish.
4. Ductility decreases.
5. Yield point phenomenon
(results in inhomogeneous
deformation), occur in
annealed steel sheet.

128. TYPES OF ROLLING PROCESSES
• CONTINOUS ROLLING
• TRANSVERSE ROLLING
• SECTION OR SHAPE ROLLING
• RING ROLLING
• THREAD ROLLING

129. CONTINOUS ROLLING
The objective is to decrease the thickness of
the metal with an increase in length and with
little increase in width.

130. TRANSVERSE ROLLING
• Using circular wedge rolls.
• Heated bar is cropped to length and fed in
transversely between rolls.
• Rolls are revolved in one direction.

131. SECTION OR SHAPE ROLLING
• Flat slap is progressively bent into complex
shapes.
• Suitable for producing moulded sections
such as irregular shaped channels and trim.

132. RING ROLLING
• A specialized type of hot rolling that increases the
diameter of a ring
• The resulting grain structure is circumferential,
which gives better mechanical properties

133. THREAD ROLLING
• Rolled threads are produced in a single pass at
speeds far in excess of those used to cut threads.
• Dies are pressed against the surface of cylindrical
blank. As the blank rolls against the in-feeding die
faces, the material is displaced to form the roots
of the thread, and the displaced material flows
radially outward to form the thread's crest.

134. TERMINOLOGY
Bloom is the product of first breakdown of ingot
(cross sectional area > 230 cm2).
Billet is the product obtained from a further
reduction by hot rolling.
(cross sectional area > 40x40 mm2).
Slab is the hot rolled ingot
(cross sectional area > 100 cm2 and with a width ≥ 2
x thickness).

135. Plate is the product with a thickness > 6 mm.
Sheet is the product with a thickness < 6 mm and
width > 600 mm.
Strip is the product with a thickness < 6 mm and
width < 600 mm.

136. Shape Rolling Operation
Structural shape rolling, also known
as shape rolling and profile rolling, is
the rolling and roll forming of structural
shapes by passing them through a rolling mill
to bend or deform the workpiece to a desired
shape while maintaining a constant cross-
section.
Structural shapes that can be made with
this metal forming process include: I-beams,
H-beams, T-beams, U-beams, angle iron,
channels, bar stock, and railroad rails.

137. Shape Rolling Operation

142. Principle of wire Drawing

143. Wire drawing is a metalworking process used to reduce
the cross-section of a wire by pulling the wire through
a single, or series of, drawing die(s).
There are many applications for wire drawing,
including electrical wiring, cables, tension-loaded
structural components, springs, paper clips, spokes for
wheels, and stringed musical instruments.
Drawing is different from extrusion, because in drawing
the wire is pulled, rather than pushed, through the die.
Drawing is usually performed at room temperature,
thus classified as a cold working process, but it may be
performed at elevated temperatures for large wires to
reduce forces.

144. Tube Drawing

145. • Tube drawing is a metalworking process to
size a tube by shrinking a large diameter tube
into a smaller one, by drawing the tube
through a die.
• This process produces high-quality tubing
with precise dimensions, good surface finish,
and the added strength of cold working.
Because it is so versatile, tube drawing is
suitable for both large- and small-scale
production.

147. There are five types of tube drawing:
• Tube sinking
• Mandrel drawing/ Rod drawing
• Stationary mandrel/ Fixed plug drawing
• Floating mandrel/ Floating plug drawing
A mandrel is used in many of the types to
prevent buckling or wrinkling in the work
piece.

149. Tube sinking
Tube sinking, also known as free tube drawing,
reduces the diameter of the tube without
a mandrel inside the tube. Especially on thick-
walled tubes and tubes smaller than 12 mm
(0.47 in) in diameter.

150. Rod drawing/Mandrel drawing
Rod drawing is the process that draws the tube
with a mandrel inside the tube; the mandrel is
drawn with the tube.
The advantage to this process is that the mandrel
defines the ID and the surface finish and has a
quick setup time for short runs.
The disadvantages are that lengths are limited by
the length of the mandrel, usually no more than
100 feet (30 m), and that a second operation is
required to remove the mandrel, called reeling.
This type of process is usually used on heavy
walled or small ID tubes.

151. Fixed plug drawing/ Stationary mandrel
Fixed plug drawing, also known as stationary
mandrel drawing, uses a mandrel at the end of
the die to shape the ID of the tube.
This process is slow and the area reductions
are limited, but it gives the best inner surface
finish of any of the processes. This is the
oldest tube drawing method.

152. Floating plug drawing/ Floating mandrel
Floating plug drawing, also known as floating
mandrel drawing, uses a mandrel that is not
anchored whatsoever to shape the ID of the tube.
The mandrel is held in by the friction forces
between the mandrel and the tube.
This axial force is given by friction and pressure.
The greatest advantage of this is that it can be used
on extremely long lengths, sometimes up to 1,000
feet (300 m).
The disadvantage is it requires a precise design
otherwise it will give inadequate results. This
process is often used for oil-well tubing.

155. Extrusion
Extrusion is a process of forcing the metal to flow
through a shape- forming die. The metal gets deformed
due to compressive and shear force applied at inlet
end.
Main advantage of extrusion is that high compressive
and shear forces are set up in the material without any
tensile forces, which makes deformation possible
without much crack formation.
Extrusion is a hot working process which makes use of
good deform ability of the material for shaping them.
The difference between the extrusion and drawing
processes lie in the fact that in drawing operation, the
metal is forced through the die by compressive forces
applied at the entry side.

156. Principle of Extrusion
• It is a primary shaping process in which a
metal kept in a cylinder is forced to pass
through the opening of a die.
• The metal is subjected to plastic
deformation and it undergoes reduction and
elongation during extrusion
Types
• Hot Extrusion
• Cold Extrusion

157. Hot extrusion: It is carried out at high
temperatures, about 50-70% of the melting
point of the metal.
cold extrusion: It is carried out at room
temperature or slightly above room
temperature.
Lead, tin, aluminium, etc can be easily extruded.

158. Hot Extrusion
• Forward Extrusion/ Direct Extrusion
• Backward Extrusion/ Indirect Extrusion
Forward Extrusion

159. • Direct extrusion, also known as forward extrusion,
is the most common extrusion process. It works by
placing the billet in a heavy walled container.
• The billet is pushed through the die by a ram or
screw. There is a reusable dummy block between
the ram and the billet to keep them separated.
• The major disadvantage of this process is that the
force required to extrude the billet is greater than
that needed in the indirect extrusion process
because of the frictional forces introduced by the
need for the billet to travel the entire length of the
container.
Forward Extrusion

160. Because of this the greatest force required is at the
beginning of process and slowly decreases as the
billet is used up.
At the end of the billet the force greatly increases
because the billet is thin and the material must flow
radially to exit the die.
The end of the billet (called the butt end) is not used
for this reason.

162. Backward Extrusion

163. Backward Extrusion
• In indirect extrusion, also known as backwards
extrusion, the billet and container move together
while the die is stationary.
• The die is held in place by a "stem" which has to be
longer than the container length.
• The maximum length of the extrusion is ultimately
dictated by the column strength of the stem.
Because the billet moves with the container the
frictional forces are eliminated

166. Cold Extrusion

167. Impact Extrusion
This method is chiefly used for making small
workpieces from ductile materials. The
material is placed in the position into a blind
die and a ram with clearance is forced into the
die making the metal to flow plastically around
the punch.
With the help of this process, collapsible
medicine tube and tooth paste tubes are
produced.
This method is restricted to soft metals as lead,
aluminium, copper, tin, etc.

168. Impact Extrusion

169. Hydrostatic Extrusion
In the hydrostatic extrusion process the billet
is completely surrounded by a pressurized
liquid, except where the billet contacts the die.
This process can be done hot, warm, or cold,
however the temperature is limited by the
stability of the fluid used.
The process must be carried out in a sealed
cylinder to contain the hydrostatic medium.

170. Hydrostatic Extrusion