Extrusion and Drawing of Metals

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Extrusion 

Extrusion and Drawing of Metals 

Slides based on Manufacturing, Engineering & Technology, Fifth Edition, by Serope Kalpakjian and 

Steven R. Schmid. 

ISBN 0-13-148965-8. © 2006 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved.

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Direct-Extrusion 

Figure 15.1 Schematic illustration of the direct-extrusion process.

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Plastic deformation process 

starts from a billet and makes long right half 

products 

Metal is pushed through a die with a narrow 

A reduction of metal section is happening 

Solid sections, bars and rods 

Tubes and hollow sections 

Very complex dies 

Extrusion breaks casted structure 

Developed 19 th Century for Pb and later Cu 

Hot and Cold Extrusion 


Basic principle

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Extrusion Parameters 

Metal properties (alloys, homogeneous) 

Temperature of the container, die, billet (preheating), stem (heat loss 

is controlled) 

Extrusion velocity 

Extrusion ratio (10-30) 

Direct of indirect extrusion 

Pressure (push up, breakthrough, max possible pressure, …) 

Size and shape of the container (round or ) 

Friction between die and container 

Design of the die (inlet angle, passl ength, laskamer, position of 

holes 

Length of the block

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Extrusion parameters (schema)

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Plastic deformation 

Usually the billet is heated (Al 300 en 500°C) to help plastic 

deformation process 

System build up stress, forces, pressure en energy 

Simpel model one has to pass level for flow stress of the metal 

Extrusion is a shear systems with gliding in the crystal structure 

(Al versus Steel) 

By friction the outer part of the metal flows slower than inner part 

resulting in a shear process 

So the outer part is feeling more shear stress 

Cold deformation if the deformation temperature is below 

recrystallisation temperature

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Dead zone 

A dead zone is created at the angles of the 

die. There the metal is not moving 

The metal shears off at this plane 

Conic form of shearing 

Dark part are oxides and inclusions 

Surface and subsurface defects occur 

(delamination, blister) 

Extrusion

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α=f(EV,σ,m,m’) 

Extrusion ratio 

m friction between billet and 

and container 

m’ friction between billet and 

die 

σ critical flow stress 


Angle of the dead zone

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10-15 % of the length of the billet 

Usually cut off 

Size depends on the extrusion 

process and metal 

Direct extrusion skin of the cast is 

collected 

Usually sufficient metal is cut off 


Butt

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Direct and Indirect Extrusion

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Direct extrusion 

Stem pushes the billet through the die 

Friction between billet and container 

Loading billet pressure builds up 

Pressure drops one the billet passes the 

die 

At the end the pressure builds up again 

Flow pattern is irregular (pressing a 

banana) 

Usable for soft alloys

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In indirect extrusion die moves into 

the billet 

No friction between billet and 

container 

Different built up of pressure 

Flow pattern is more uniform 

Force is lower good for harder 

alloys 

Casted metal has to be scalped 


Indirect extrusion

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Advantages of indirect extrusion 

• Long billets = higher efficiency 

Indirect vs Direct Extrusion 

• Higher extrusion speed possible (less temperature raise no friction) 

• Equal pressure over the process, better tolerance 

Disadvantages of indirect extrusion 

• Higher surface risk (delamination under the surface) 

• Smaller die surface hollow stem 

• Hollow stem, so quenching is difficult. So separate heat treatments necessary. 

• Higher cost 

• More complicated process 


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Extrusions and Products Made from Extrusions 

Figure 15.2 Extrusions and 

examples of products made by 

sectioning off extrusions. 

Source: Courtesy of Kaiser 

Aluminum.

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Types of Extrusion 

Figure 15.3 Types of extrusion: (a) indirect; (b) hydrostatic; (c) lateral;

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Process Variables in Direct 


Figure 15.4 Process variables in direct extrusion. The die angle, reduction in cross-section, 

extrusion speed, billet temperature, and lubrication all affect the extrusion pressure.

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Extrusion Force 

Extrusion force, F = Aol ln A ⎛ ⎞ 

o 

⎜ ⎟ 

⎝ A f ⎠ 

Figure 15.5 Extrusion constant k for 

various metals at different 

temperatures. Source: After P. 

Loewenstein

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Types of Metal Flow in Extrusion with Square Dies 

Figure 15.6 Types of metal flow in extruding with square dies. (a) Flow pattern obtained at 

low friction or in indirect extrusion. (b) Pattern obtained with high friction at the billetchamber 

interfaces. (c) Pattern obtained at high friction or with coiling of the outer regions of 

the billet in the chamber. This type of pattern, observed in metals whose strength increases 

rapidly with decreasing temperature, leads to a defect known as pipe (or extrusion) defect.

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Extrusion Temperature Ranges

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Extrusion-Die Configurations 

Figure 15.7 Typical extrusion-die configurations: (a) die for nonferrous metals; (b) die 

for ferrous metals; (c) die for a T-shaped extrusion made of hot-work die steel and 

used with molten glass as a lubricant. Source: (c) Courtesy of LTV Steel Company.

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Extrusion in Creation of Intricate Parts 

Figure 15.8 (a) An extruded 6063-T6 aluminum-ladder lock for aluminum extension ladders. 

This part is 8 mm (5/16 in.) thick and is sawed from the extrusion (see Fig. 15.2). (b-d) 

Components of various dies for extruding intricate hollow shapes. Source: (b-d) After K. 

Laue and H. Stenger

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Extrusion of Heat Sinks 

Figure 15.10 (a) Aluminum extrusion used as a heat sink for a printed circuit board. (b) 

Die and resulting heat sink profiles. Source: Courtesy of Aluminum Extruders Council. 


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Chevron Cracking 

Figure 15.16 (a) Chevron cracking (central burst) in extruded round steel bars. 

Unless the products are inspected, such internal defects may remain undetected 

and later cause failure of the parts in service. This defect can also develop in 

the drawing of rod, of wire, and of tubes. (b) Schematic illustration of rigid and 

plastic zones in extrusion. The tendency toward chevron cracking increases if 

the two plastic zones do not meet. Note that the plastic zone can be made larger 

either by decreasing the die angle or by increasing the reduction in crosssection 

(or both). Source: After B. Avitzur.

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9-MN (1000-ton) Hydraulic- 

Extrusion Press 

Figure 15.17 General view of a 9-MN (1000-ton) hydraulic-extrusion press. 

Source: Courtesy of Jones & Laughlin Steel Corporation.

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Process Variables in Wire Drawing 

Figure 15.18 Process variables in wire drawing. The die angle, the reduction in crosssectional 

area per pass, the speed of drawing, the temperature, and the lubrication all affect 

the drawing force, F.

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Tube-Drawing Operations 

Figure 15.19 Examples of tube-drawing operations, with and without an internal 

mandrel. Note that a variety of diameters and wall thicknesses can be produced 

from the same initial tube stock (which has been made by other processes).

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Figure 15.20 Terminology of a 

typical die used for drawing a 

round rod or wire. 


Drawing Dies 

Figure 15.21 Tungsten-carbide die 

insert in a steel casing. Diamond 

dies used in drawing thin wire are 

encased in a similar manner.

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Extruded Channel on a Draw Bench 

Figure 15.22 Cold drawing of an extruded channel on a draw bench to 

reduce its cross-section. Individual lengths of straight rods or of crosssections 

are drawn by this method. Source: Courtesy of The Babcock and 

Wilcox Company, Tubular Products Division.

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Multistage Wire-drawing Machine 

Figure 15.23 Two views of a multistage wire-drawing machine that typically is used 

in the making of copper wire for electrical wiring. Source: After H. Auerswald

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Gegoten perspalen 


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Transport

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Transport

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ABS 

PSA 

Monotube Shock-Absorber & 

Strut 

Renault 

Automotive 

Transmission Valves 

General Motors 

Daimler Chrysler 

Airbag 

PSA 

Forged Pressure Regulator 

Daimler Chrysler 

Brake Piston & Regulator 

Renault & PSA 

Ford / BMW

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Civil

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Sport, Engineering

Extrusion and Drawing of Metals

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