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Extrusion and Drawing
Mechanical Working of Metals
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Definition of Extrusion
The basic
process of
forcing a metal
billet through ashaped die
Mainly used forSoft Metals such
as Aluminum or
Copper and
done hot
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EXTRUSION
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Tools in Extrusion
RAM DIE
http://www.precision-terrafirma.com/images/extrusiondies/ExtrusionDies2.jpghttp://www.kamkiu.com/My%20Webs/kk-English/extrusion_ram.jpg7/29/2019 Mechanical Working of Metals (Extrusion and Drawing)
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Extrusion Products
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SOLID
Cross Sections
HOLLOW
Cross Sections
PRODUCTS OF
EXTRUSION
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Types of Extrusion
Direct Extrusion
ram is separate
from the die
IndirectExtrusion
ram is with die
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Direct and Indirect Extrusion
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Difference between Direct and
Indirect Extrusion
Indirect Extrusion
requires lower
extrusion loads
since less frictionis encountered!
Disadvantage in Indirect
Extrusion:
a) Difficulty in supporting
extruded products
b) Lower rigidity of die
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Extrusion Load Profile
Increases initially
as metal is being
upset into die
Increases
after 85% of
the metal hasbeen
extruded
Load
Decreases
during
extrusion
proper
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Extrusion Ratio
rx= extrusion ratioAo = area initial
Af = area final
Extrusion ratio of 35:1
to 100:1 is done in the
industry!
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Extrusion Work
Work = Force x Distance
Wx = xV lnr
Extrusion ratio affects the
amount of work required to
do extrusion!
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Effect of Die Angle on
Extrusion Load
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Effect of Die Angle
Low die angle
surface area is large, leading to:
increased friction at die-billet interface & higher
friction results in larger ram force
Large die angle
more turbulence in metal flow during reduction:
Turbulence increases ram force required
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Optimum Die Angle
Optimum angle depends on work material, billet
temperature, and lubrication!
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Redundant Work
Refers to work required to bend the metal one way
and then bend it back to its original direction!
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Effect of Die Shape on
Extrusion Load
VS
As the die orifice shape becomes more
complex, higher loads are required!
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Extrusion Load Analysis
USE SLAB METHOD TO DETERMINE
EXTRUSION LOAD
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Actual Extrusion Pressure
044
2
0
2
0 d
ddPd
d xxoxx
o
oxd
x
4exp
Summation of Forces along the horizontal:
x = extrusion pressure profile
when length x is inside the
container
o = yield stress
= coefficient of friction
do = initial diameter
x = length of billet inside thecontainer
o
oxd
x
41
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Sample Problem
A 4 long billet with diameter = 1.25 is direct
extruded to a diameter of 0.50. For the work
metal, y = 45,000 lb/in2 and coefficient of
friction is 0.30.
Determine:
(a) extrusion ratio
(b) extrusion strain
(c) ram pressure at L = 4.0, 2.5, 1.0 and 0.
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Mean Extrusion Pressure
o
oxd
x
41
o
oo
dL 41max o min
o
omeand
L
21
2
minmax
When L = Lo When L =0
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Extrusion Load
o
o
oox A
d
LF
21
Extrusion Force = Mean Pressure x Area of Contact
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Extrusion Work
rVd
LWo
oextrusion ln21
This work equation may also betransformed to calculate for the
power required to extrude a metal!
Wx = xV lnrRECALL:
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Sample Problem
For the given extrusion problem, if the ram was
moved at a rate of 1.0 per 150 seconds,
determine:
(a) mean extrusion load
(b) extrusion work
(c) power required for this operation(1 HP = 33,000 ft-lb/min)
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Sample Problem
During the extrusion of a steel billet 1.5 m
long, 640 mm diameter it was noted that
the extrusion load was 128 MN when the
ram was 1/3 of the way through the cycleand 111.6 MN when through. Calculate
the coefficient of friction in the chamber.
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Wire Drawing
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Definition of Wire Drawing
Wire drawing is a metal-reducing process
in which a wire rod is pulled through a
single die or a series of continuous dies,
thereby reducing its diameter.
Various wire temperscan be produced by
a series of drawing and annealing
operations. (Temperrefers to toughness.)
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Wire Drawing
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Deep Drawing
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Products of Deep Drawing
http://images.google.com.ph/imgres?imgurl=http://www.alfed.net/images/Pots.jpg&imgrefurl=http://www.alfed.net/health.htm&h=337&w=484&sz=28&tbnid=Pq16L_ePl0sJ:&tbnh=87&tbnw=125&start=6&prev=/images%3Fq%3Dmetal%2Bcooking%2Bpots%26hl%3Dtl%26lr%3Dhttp://images.google.com.ph/imgres?imgurl=http://www.txantiquemall.com/2step/c2_bullets.gif&imgrefurl=http://www.txantiquemall.com/2step/2step_c.htm&h=142&w=150&sz=17&tbnid=Dehvz-Ifs2EJ:&tbnh=85&tbnw=90&start=2&prev=/images%3Fq%3Dbullet%2Bcasings%26hl%3Dtl%26lr%3D%26sa%3DNhttp://www.pmfind.com/images4/preform1.jpg7/29/2019 Mechanical Working of Metals (Extrusion and Drawing)
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Wire Drawing Products
WIRES
ROD STOCKS
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Die Tandem
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Drawing Series
Since wire drawing is normally done cold,annealing is sometimes necessary
between dies
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Drawing Die
The longer the bearing, the
longer the life of the die!
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Features of a Draw Die
a) Entryregion - funnels lubricant into the die to
prevent scoring of work and die
b) Approach- cone-shaped region where drawingoccurs
c) Bearing su rface- determines final stock size
d) Back rel ief- exit zone - provided with a backrelief angle(half-angle) of about 30
Die materials: tool steels or cemented carbides
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Extrusion vs Drawing
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Drawing Load
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Drawing Load Analysis
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Drawing Stress
Slab analysis will yield the equation for the
drawing stress as follows:
B
o
f
odd
d
B
B2
11
B= cot
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Drawing Load
4
11
22
f
B
o
f
od
d
d
d
B
BF
Drawing Load = Drawing Stress x Final Area
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Drawing Strain
Drawing Strain is expressed in terms ofreduction in area, R
o
fo
AAAR
Ao = area initial
Af= area final
In Drawing, maximum possible drawing strain is achieved
when:
drawing stress = flow stress of metal
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Sample Problem
Determine the maximum possible drawing
strain if steel wire (YS=140 MPa) is drawn
with die angle 4o
and coefficient of frictionis 0.20.
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Sample Problem
Rod stock is drawn through a draw die with anentrance angle(2) of 12. Starting diameter =0.50 and final diameter = 0.35. Coefficient of
friction at the die-work interface = 0.10.Determine:
(a) area reduction
(b) drawing load for the operation(c) horsepower to perform the operation if theexit velocity of the stock = 2 ft/sec.
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Sample Problem
Calculate the drawing load required to
achieve 30% reduction in area on a 10-
mm diameter copper wire, given that the
yield stress of the metal is 235 MPa, dieangle is 8o and coefficient of friction is
0.08.
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Advantages of Hot Working
Decrease in energy required for
deformation
Increased ability of metal to flow without
cracking
Rapid diffusion decreases chemical
inhomogeneities
Elimination of blowholes and porosities
Refinement of coarse columnar grains to
fine equiaxed grains
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Disadvantages of Hot Working
Oxidation results to metal losses
Reactive metals require inert atmosphere
Decarburization of steels
Poor surface finish
Greater dimensional tolerance required
Less uniform structure and properties
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Ideal Extrusion Load
Work = Force x Distance
Wx = yV lnr
Px = y
lnr
Fx = ylnrAo