1. 7/14/2015
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Extrusion & Drawing Extrusion
 The extrusion process is like squeezing toothpaste out of
a tube.
 Metal is compressed and forced to flow through a
suitably shaped die to form a product with reduced but
constantcross section.
 Metal will undergo tri-axial compression.
 Hotextrusion is commonlyemployed.
 Lead, copper, aluminum, magnesium, and alloys of these
metals are commonlyextruded.
 Steels, stainless steels, and nickel-based alloys are
difficult to extrude. (high yield strengths, welding with
wall). Use phosphate-based and molten glass
lubricants.
Extrusion Ratio
 Ratio of the cross-sectional area of the billet to the cross-
sectional area of the product.
 about 40: 1 for hot extrusion of steel
 400: 1 foraluminium
Advantages of Extrusion
 Any cross-sectional shape can be extruded from the
nonferrous metals.
 Many shapes (than rolling)
 No draft
 Huge reduction in cross section.
 Conversion from one product to another requires only a
single die change
 Good dimensional precision.

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Limitation of Extrusion
 Cross section must be uniform for the entire length of
the product.
Application
 Working of poorly plastic and non ferrous metals and
alloys.
 Manufacture of sections and pipes of complex
configuration.
 Medium and small batch production.
 Manufactureof parts of high dimensional accuracy.
Hot Extrusion Process
 The temperature range for hot extrusion of aluminum is
430-480°C
 Used to produce curtain rods made of aluminum.
 Design of die is a problem.
 Eitherdirect or indirectmethod used.
Direct Extrusion
 A solid ram drives the entire billet to and through a
stationary die and must provide additional power to
overcome the frictional resistance between the surface of the
moving billet and the confining chamber.
Indirect Extrusion
 A hollow ram drives the die back through a stationary,
confined billet.
 Since no relative motion, friction between the billet and
the chamber is eliminated.

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Indirect Extrusion Contd…
 Required force is lower (25 to 30% less)
 Low process waste.
Cold Extrusion
 Used with low-strength metals such as lead, tin, zinc,
and aluminum to produce collapsible tubes for
toothpaste, medications, and other creams; small "cans"
for shielding electronic components and larger cans for
foodand beverages.
 Now-a-days also been used for forming mild steel parts.
Backward cold extrusion
 The metal is extruded through the gap between the
punch and die opposite to the punch movement.
 Forsofter materials such as aluminium and its alloys.
 Used for making collapsible tubes, cans for liquids and
similararticles.
Impact Extrusion
 The extruded parts are stripped by the use of a stripper
plate, because they tend to stick to the punch.
Hooker Method Hooker Method
 The ram/punch has a shoulder and acts as a mandrel.
 A flat blank of specified diameter and thickness is placed in a
suitable die and is forced through the opening of the die with
the punch
 when the punch starts downward movement. Pressure is
exerted by the shoulder of the punch, the metal being forced
to flow through the restricted annular space between the
punch and the opening in the bottom of the die.
 In place of a flat solid blank, a hollow slug can also be used.
 If the tube sticks to the punch on its upward stroke, a
stripper will strip it from the punch.
 Small copper tubes and cartridge cases are extruded by this
method.

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Hydrostatic Extrusion
 Anothertype of cold extrusion process.
 High-pressure fluid applies the force to the workpiece
through a die.
 It is forward extrusion, but the fluid pressure
surrounding the billet prevents upsetting.
 Billet-chamber friction is eliminated, and the
pressurized fluid acts as a lubricant between the billet
and the die.
Hydrostatic Extrusion Contd….
Hydrostatic Extrusion Contd….
 Temperature is limited since the fluid acts as a heat sink
and the common fluids (light hydrocarbons and oils)
burn or decomposesat moderately low temperatures.
 The metal deformation is performed in a high-
compression environment. Crack formation is
suppressed, leading to a phenomenon known as
pressure-inducedductility.
 Relatively brittle materials like cast iron, stainless steel,
molybdenum, tungsten and various inter-metallic
compounds can be plastically deformed without
fracture, and materials with limited ductility become
highly plastic.
Application
 Extrusion of nuclear reactor fuel rod
 Making wires for less ductile materials
Lubrication for Extrusion
 For hot extrusion glass is an excellent lubricant with
steels, stainless steels and high temperature metals and
alloys.
 For cold extrusion, lubrication is critical, especially with
steels, because of the possibility of sticking (seizure)
between the workpiece and the tooling if the lubrication
breaks down. Most effective lubricant is a phosphate
conversioncoating on the workpiece.
IES 2009 Conventional

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Wire Drawing
 A cold working process to obtain wires from rods of
bigger diameters through a die.
 Same process as bar drawing except that it involves
smaller-diametermaterial.
 At the start of wire drawing, the end of the rod or wire to
be drawn is pointed (by swaging etc.) so that it freely
enters the die orificeand sticks out behind the die.
Wire Drawing Contd….
Wire Drawing Contd….
 Wire getting continuouslywound on the reel.
 For fine wire, the material may be passed through a
number of dies, receiving successive reductions in
diameter, before being coiled.
 The wire is subjected to tension only. But when it is in
contact with dies then a combination of tensile,
compressive and shear stresses will be there in that
portiononly.
Cleaning and Lubrication in wire Drawing
 Cleaning is done to remove scale and rust by acid pickling.
 Lubrication boxes precede the individual dies to help reduce
friction drag and prevent wear of the dies.
 Sulling: The wire is coated with a thin coat of ferrous
hydroxide which when combined with lime acts as filler for
the lubricant.
 Phosphating: A thin film of Mn, Fe or Zn phosphate is
applied on the wire.
 Electrolytic coating: For very thin wires, electrolytic coating
of copper is used to reduce friction.
Wire Drawing Die
 Die materials: tool steels or tungsten carbides or
polycrystallinediamond (for fine wire)
Rod and Tube Drawing
 Rod drawing is similar to wire drawing except for the
fact that the dies are bigger because of the rod size
being larger than the wire.
 The tubes are also first pointed and then entered
through the die where the point is gripped in a similar
way as the bar drawing and pulled through in the form
desired along a straight line.
 When the final size is obtained, the tube may be
annealed and straightened.
 The practice of drawing tubes without the help of an
internal mandrel is called tube sinking.

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Back
Rod and Tube Drawing Contd…
Tube Sinking Fixed Plug Drawing
Floating plug Drawing Moving Mandrel
Swaging or kneading
 The hammering of a rod or tube to reduce its diameter
where the die itself acts as the hammer.
 Repeated blows are delivered from various angles,
causing the metal to flow inward and assume the shape
of the die.
 It is cold working. The term swaging is also applied to
processes where material is forced into a confining die to
reduce its diameter.
Swaging or kneading Contd…
Extrusion Load
 Approximate method (Uniform deformation, no friction)
“work – formula”
 For real conditions
K = extrusion constant.
ln o
o o
f
A
P A
A

 
  
 
 
ln o
o
f
A
P KA
A
 
  
 
 
Force required in Wire or Tube drawing
 Approximate method (Uniform deformation, no friction)
“work – formula”
ln o
f o
f
A
P A
A

 
  
 
 

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Wire Drawing
 
2 2
1
1 .
B B
f f
o
d b
o o
r r
B
B r r

 
 
    
 
  
   
 
   
 
f
Maximum Reduction per pass
 
2 2
With back stress,
1
1 .
b
B B
f f
o
o b
o o
r r
B
B r r


 
 
    
 
  
   
 
   
 
 
2
Without backstress,
1
1
b
B
f
o
o
o
r
B
B r



 
  
 
   
 
 
 
GATE – 2011 (PI) Common Data-S1
In a multi-pass drawing operation, a round bar of 10 mm
diameter and 100 mm length is reduced in cross-section
by drawing it successively through a series of seven dies
of decreasing exit diameter. During each of these
drawing operations, the reduction in cross-sectional area
is 35%. The yield strength of the material is 200 MPa.
Ignore strain hardening.
The total true strain applied and the final length (in
mm), respectively, are
(a) 2.45 and 8 17 (b) 2.45 and 345
(c) 3.02 and 2043 (d) 3.02 and 3330
GATE – 2011 (PI) Common Data-S2
In a multi-pass drawing operation, a round bar of 10 mm
diameter and 100 mm length is reduced in cross-section
by drawing it successively through a series of seven dies
of decreasing exit diameter. During each of these
drawing operations, the reduction in cross-sectional area
is 35%. The yield strength of the material is 200 MPa.
Ignore strain hardening.
Neglecting frictionand redundant work, the force (in
kN) required fordrawing the bar through the first die, is
(a) 15.71 (b) 10.21
(c) 6.77 (d) 4.39

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GATE-2006
In a wire drawing operation, diameter of a steel wire
is reduced from 10 mm to 8 mm. The mean flow
stress of the material is 400 MPa. The ideal force
required for drawing (ignoring friction and
redundantwork) is
(a) 4.48 kN (b) 8.97 kN
(c) 20.11 kN (d) 31.41 kN
GATE-2001, GATE -2007 (PI)
For rigid perfectly-plastic work material, negligible
interface friction and no redundant work, the
theoretically maximum possible reduction in the
wiredrawing operation is
(a) 0.36 (b) 0.63
(c) 1.00 (d) 2.72

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GATE -2008 (PI) Linked S-1
A 10 mm diameter annealed steel wire is drawn through
a die at a speed of 0.5 m/s to reduce the diameter by
20%. The yield stress of the material is 800 MPa.
Neglecting friction and strain hardening, the stress
required fordrawing (in MPa) is
(a) 178.5 (b) 357.0 (c) 1287.5 (d) 2575.0
GATE -2008 (PI) Linked S-2
A 10 mm diameter annealed steel wire is drawn through
a die at a speed of 0.5 m/s to reduce the diameter by
20%. The yield stress of the material is 800 MPa.
The power required for the drawing process (in kW) is
(a) 8.97 (b) 14.0 (c) 17.95 (d) 28.0
GATE-2003
A brass billet is to be extruded from its initial
diameter of 100 mm to a final diameter of 50 mm.
The working temperature of 700°C and the
extrusion constant is 250 MPa. The force required
forextrusion is
(a) 5.44 MN (b) 2.72 MN
(c) 1.36 MN (d) 0.36 MN

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GATE – 2009 (PI)
Using direct extrusion process, a round billet of 100 mm
length and 50 mm diameter is extruded. Considering an
ideal deformation process (no friction and no redundant
work), extrusion ratio 4, and average flow stress of
material 300 MPa, the pressure (in MPa) on the ram will
be
(a) 416 (b) 624 (c) 700 (d) 832
GATE – 2014
 A metal rod of initial length is subjected to a
drawing process. The length of the rod at any
instant is given by the expression, L(t) = Lo(1 + t2)
where t is the time in minutes. The true strain
rate at the end of one minute is ………..
IES - 2012
Which of the following are correct for an indirect hot
extrusion process?
1. Billetremains stationary
2. There is no friction force between billet and container
walls.
3. The force required on the punch is more in
comparisonto directextrusion.
4. Extrusion parts have to be provided a support.
(a) 1, 2, 3 and 4 (b) 1, 2 and 3 only
(c) 1, 2 and 4 only (d) 2, 3 and 4 only
IES - 2012
Extrusion process can effectively reduce the cost of
productthrough
(a) Material saving
(b) process time saving
(c) Saving in tooling cost
(d) saving in administrative cost

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IES – 1993
Tandem drawing of wires and tubes is necessary
because
(a) It is not possible to reduce at one stage
(b) Annealing is needed between stages
(c) Accuracyin dimensions is not possible otherwise
(d) Surface finish improves after every drawing stage
IES 2011
Match List –I with List –II and select the correct answer using
the code given below the lists :
Codes
A B C D A B C D
(a) 2 1 4 3 (b) 3 1 4 2
(c) 2 4 1 3 (d) 3 4 1 2
List –I List –II
A. Connecting rods 1. Welding
B. Pressure vessels 2. Extrusion
C. Machine tool beds 3. Forming
D. Collapsible tubes 4. Casting
Wire Drawing Analysis (Home Work)
   2 2
Theequilibriumequation in x-direction willbe
cos 2
cos
sin 2 0
cos
x x x x
x
dx
d r dr r r
dx
P r
       

 

 
     
 
 
 
 
 
 
2
2
2 2 2 tan 0
Dividing by r dr and taking dx/dr = cot we get
2
2
cot 0
Vertical component of due to small half die
angles and that of can beneglected.
Thefore,
x x x x
x x
x x
x x
x
or rdr d r r dx P rdx
d
P
dr r r
P P
   

 
 

   
   

 
twoprincipal stresses are and
BothTresca'sand Von-Misescriteria willgive
and
x x
x x o
x x o x
P
P
P

 
    

 
  
 
 
 
   
2
2
cot 0
Let cot
2
1
2
1
Integratingbothside
1
ln 1 2ln
{Cisintegrationcont.}
o x
x o
x
x o
x
x o
x o
d
dr r r
B
d
B B
dr r
d
or dr
r
B B
B B rC
B
  
 

 

 

 
 

  

  
 
 

 
 
 
   
 
 
   
 
 
 
2
1
2
2 2
2 2
1
. ,
1
1
1 .
1
( ) 1 .
B
x o
s
o x b
B
b o
o
B B
o
x b
o o
B B
f f
o
d b
o o
or B B rC
BC atr r
B B
C
r
B r r
or
B r r
r r
B
Drawing stress
B r r
 
 
 

 

 
  
 
 
 
 
 
 
    
 
  
   
 
   
 
 
    
 
   
   
 
   
 

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Extrusion Analysis (Home Work)
   
 
 
s
2
1
2
2
Fora round bar both wiredrawing and extrusion willgive
same equation except B.C
1
. , 0 (at exit stressiszero)
1
1
1
B
x o
s
f x
B
o
f
B
o
x
f
B B rC
B C at r r
B
C
r
B r
or
B r
 




   
 
 
 
 
 
 
 

 
   
 
 
 
 
 
 
2
2
2
1
1
Extrusion ratio, for round bar
forflat stock
1
1
o
B
o o
xo
f
o o
f f
o
f
o B
xo
at r r
B r
B r
A r
R
A r
h
h
B
R
B





 
 

 
   
 
 
 
 
 
   
 
 
 
  
 
 

 
 
 
2
0 0
t
If effect of container friction isconsidered
rampressurerequired bycontainer friction
uniforminterfaceshearstressbetween
billet and container wall
2
. 2
TotalExtrusion Pressure(P )
a
f
i
i
f i f
o
xo f
p
L
p r r L or p
r
p


  



 
  
2
0
nd Extrusion Load .
t
p r

