Extrusion process

1. Extrusion process
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2. Hot working and cold working of metals –
Forging processes – Open, impression
and closed die forging – forging
operations. Rolling of metals– Types of
Rolling – Flat strip rolling – shape rolling
operations – Defects in rolled parts.
Principle of rod and wire drawing –
Tube drawing – Principles of Extrusion
– Types – Hot and Cold extrusion.YoucaN

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8. • In extrusion, a cylindrical billet is forced through a die in a
manner similar to squeezing toothpaste from a tube In
various cross sections.
• A wide variety of solid or hollow cross sections may be
produced by extrusion.
• Large deformations can take place without fracture
because the material is under high triaxial compression.
• Since the die geometry remains unchanged throughout the
operation, extruded products typically have a constant
cross section.
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9. • Commonly extruded materials are aluminum, copper, steel,
magnesium, and lead.
• Depending on the ductility of the material, extrusion is carried
out at room or elevated temperatures. Extrusion at room
temperature often is combined with forging operations, in
which case it generally is known as cold extrusion.
• extruded products have an elongated grain
structure (preferred orientation).
• variables are
• the temperature of the billet, the speed at which the ram travels,
and the type of lubricant used.
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10. • Die materials
• Hot worked die steels
• Zirconia dies
• Lubrications
• Before the billet is placed in the chamber, its cylindrical
surface is coated with a layer of powdered glass to
develop a thin glass lubricant layer at the billet-chamber
interface.
• Highly sticking material is placed in container with a thin
walled container or jacket made of lower strength metal
such as copper or mild steel.
Pressures range from 30 to 700 MPa
Oil or graphite for lower
temperature extrusions, or glass
powder for higher temperature
extrusions
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11. • Hot extrusion- Direct extrusion
-Indirect extrusion
• Cold extrusion- Impact extrusion
-Solid and hollow objects
• Hydrostatic extrusion
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12. variables are
the temperature of the billet, the speed at
which the ram travels, and the type of lubricant
used. YoucaN

13. • Extruded
products have
an elongated
grain structure
(preferred
orientation).
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14. • For metals and alloys that do not have sufficient
ductility at room temperature, or in order to reduce the
forces required, extrusion is carried out at elevated
temperatures
• As in all other hot-working operations, hot extrusion has
special requirements because of the high operating
temperatures.
Hot extrusion temperature for various
metals[1]
Material Temperature °C
Magnesium 350–450
Aluminium 350–500
Copper 600–1100
Steel 1200–1300
Titanium 700–1200
Nickel 1000–1200
Refractory
up to 2000
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15. • Hot extrusion process the billets are heated above
recrystalline temperature. To reduce cooling of
the billet and to prolong die life, extrusion dies may be
preheated.
• The billet is in hot condition so it develops oxide layer.
The oxide layer will affect the flow pattern of the
extruded metal.
• It act as a abrasive layer. To prevent this a dummy block
is placed ahead of the ram. It is little smaller in diameter
than the container. (it avoids the maximum friction force
resistance)
• As a result, a thin shell (skull) is removed from the
chamber. YoucaN

16. • Die design
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17. • Die materials
• Hot worked die steels
• Zirconia dies
• Lubrications
• Before the billet is placed in the chamber, its cylindrical
surface is coated with a layer of powdered glass to
develop a thin glass lubricant layer at the billet-chamber
interface.
• Highly stickinga material is placed in container with a thin
walled container or jacket made of lower strength metal
such a s copper or mild steel.
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18. • Heated billet is placed in the press which is operated by
the ram and a cylinder.
• The heated metal billet is pushed by the ram and with the
application of ram pressure the metal first plastically fills
the die.
• Then it is forced out through the die opening and finally
cut at the die face.
• Lubrications pressure
• Oil or graphite 30 to 700 MPa
Die materials
Hot worked die steels
Zirconia dies
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Dummy block

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For hollow objects

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28. • The function of dummy block is to protect the pressing strem tip
in the extrusion process. Also retain the oxide layers in the metal
surface.
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29. • Here the die moves towards the unextruded billet.
• Indirect extrusion has the advantage of having no billet-
container friction, since there is no relative motion.
• Thus, indirect extrusion is used on materials with very high
friction, such as high strength steels.
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30. Indirect extrusion
Solid part
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5. Cannot be used fro longer components5. Can be used fro longer components

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36. • In cold extrusion process the metals have a high degree off
ductility.
• Cold extrusion process improves the physical properties of
a metal and to produce a good accurate dimensioned
objects.
• The production rate is fairly high giving about 60 components
per minute.
• The main advantages of this process are, it speeds up the
product uniformity and lowers scrap yield.
• Cold extrusion is used Widely for components in
automobiles, motorcycles, bicycles, and appliances and
in transportation and farm equipment.
• The various items of daily use such as tubes for shaving
creams, tooth pastes and paints, condenser cans and thin
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37. • The working principle of this process is that the work
material is placed between the die and ram.
• The punch is connected with the ram.
• When the sudden impact is given to the ram, the metal
flows plastically in the upward direction, metals such
as aluminium, tins are extruded in an impact
extrusion.
• The metal flows up along the surface of the punch
forming a cup shaped component.
• When the punch moves up, the stripper OR compressed
air is used to separate the component from the punch.
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38. • Cold extrusion fig
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39. • Punch – blank on a die – downward motion of punch – blank
forced to flow through the restricted annular space.
• Used to manufacture a small copper tubes.
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42. • In hydrostatic extrusion, the billet is smaller in diameter
than the chamber (which is filled with a fluid), and the
pressure is transmitted to the fluid by a ram.
• The fluid pressure results in triaxial compressive
stresses acting on the workpiece and thus improved
formability; also, there is much less workpiece- container
friction than in direct extrusion.
• A less common type of extrusion is lateral (or side)
extrusion
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In this process extrusion ratio is
20 for steels
200 for alluminium

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44. • Advantage
• No friction between container and billet
• Brittle material can be extruded by this method.
• Uniform flow of material
• No billet residue is left on the walls of container
• Disadvantage
• Difficult to contain the fluid under the effects of high pressure
(2Gpa)
• Decreased process efficiency in terms of billet to container
volume ratio
• Billets have to be prepared by tapering one end so that it
matches the die entry angle.
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46. • Automation possible
• Small parts in large quantities is possible
• Extruded Products are lighter and stronger than casting
• Dimensional accuracy is good
• Secondary operations are not needed
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47. • Unextruded billet is a waste one
• Cost of extrusion is high
• Service life of extrusion tooling is shorter(bez high
stresses)
• Only constant shapes can be manufactured
• If the length of the billet is increased, the
corresponding extrusion pressure is also higher
because of friction between container and billet.
Therefore, billet lengths beyond 5 times the
diameter are not preferred in direct extrusion.
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48. • It is a cold working process in which the workpiece is
pulled through a tapered hole in a die so, the diameter
is reduced.
• Wire can not be hot rolled economically smaller than
5mm dia. So cold working is mainly used in wire
production
• The starting material input for drawing is from the
extruded or rolled rods of 5 to 9mm.
• Preparation of wire is important.(surface cleaning)
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49. • The die geometry is typically a bell shaped one.
• The land serves to guide the wire or rod as it comes out
of the working zone of the die.
• Material below 16mm diameter are handled in coil form.
• The one end of the wire is gripped with a plier or
carriage which pulls the rod through all zones of the die
hole where it under goes deformation or elongation. Then
it is rolled on a power reel.
• Then the power reel rotates at a proper speed and pulls
the wire.
• Coil speed is 25m/s.
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50. • fig
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52. • Same as wire drawing process, here the product must
remain straight
• The maximum length depends upon the carriage
movement distance
• Here a moving chain arrangement is used to pull the
rod with a help of hook.
• The pull capacity is 10kN to 1500kN.
• Drawing speed may be
For larger size rod 0.15m/s
For smaller size rod 1.5m/s
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54. • Tube sinking
• Tube drawing
• Tube extrusion
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55. • Tube sinking, also known as free tube drawing, reduces the
diameter of the tube without a mandrel inside the tube.
• This type of drawing operation is the most economical,
especially on thick-walled tubes and tubes smaller than
12 mm in diameter, but does not give the best surface finish.
As the tube thickness increases the surface finish quality
decreases. This process is often used for the tubing on low-
cost lawn furniture.
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