Extruded products constitute more than 50 % of the
market for aluminium products in Europe of which the building
industry consumes the majority. Aluminium extrusions are used
in commercial and domestic buildings for window and door frame systems,
prefabricated houses/building structures, roofing and exterior cladding,
curtain walling, shop fronts, etc. Furthermore, extrusions are also
used in transport for
airframes, road and rail vehicles and in marine applications. What is Extrusion?
The
term extrusion is usually applied to both the process, and the product
obtained, when a hot cylindrical billet of
aluminium is pushed through a shaped die (forward or direct extrusion,
see Figure 1). The resulting section can be used in long lengths or
cut into short parts for use in structures, vehicles or components.
Also, extrusions are used for the starting stock for drawn rod, cold
extruded and forged products. While the majority of the many hundreds
of extrusion presses used throughout the world are covered by the simple
description given above it should be noted that some presses accommodate
rectangular shaped billets for the purpose of producing extrusions
with wide section sizes. Other presses are designed to push the die
into the billet. This latter modification is usually termed "indirect" extrusion.
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| Figure 1. Schematic of the
extrusion process. |
The Versatility of the Extrusion Process
The versatility of the process in terms of both alloys
available and shapes possible makes it one of the most valued assets
in helping the aluminium producer supply users with solutions to their
design requirements. The Extrusion Process
The
fundamental features of the process are as follows: A heated billet
cut from
DC cast log (or for small diameters from larger
extruded bar) is located in a heated container, usually around 450°C
- 500°C. At these temperatures the flow stress of the aluminium alloys
is very low and by applying pressure by means of a ram to one end of
the billet the metal flows through the steel die, located at the other
end of the container to produce a section, the cross sectional shape
of which is defined by the shape of the die. Aluminium Alloys and Extrusion
All
aluminium alloys can be extruded but some are less suitable than
others, requiring
higher pressures, allowing only
low extrusion speeds and/or having less than acceptable surface finish
and section complexity. The term ‘extrudability’ is used to embrace
all of these issues with pure aluminium at one end of the scale and
the strong aluminium/zinc/magnesium/copper alloys at the other end.
The biggest share of the extrusion market is taken by the 6000, AlMgSi
series. This group of alloys have an attractive combination of properties,
relevant to both use and production and they have been subject to a
great deal of R & D in many countries. The result is a set of materials
ranging in strength from 150 MPa to 350 MPa, all with good toughness
and formability. They can be extruded with ease and their overall ‘extrudability’ is
good but those containing the lower limits of magnesium and silicon
e.g. 6060 and 6063 extrude at very high speeds - up to 100 m/min with
good surface finish, anodising capability and maximum complexity of
section shape combined with minimum section thickness. Extrusion Machines
Press load capacities range from a few hundred tonnes
to as high as 20,000 tonnes although the majority range between 1,000
and 3,000 tonnes. Billet sizes cover the range from 50 mm diameter
to 500 mm with length usually about 2-4 times the diameter and while
most presses have cylindrical containers a few have rectangular ones
for the production of wide shallow sections. Design Aspects of Aluminium Extrusions
Inal Metals are a solution driven innovator that
design, manufacture and supply aluminium extrusions and fabricated
aluminium components.
Operating from our site in Manchester we can supply
throughout the UK and worldwide. Accredited to ISO 9001:2000, our premise
is simple “To understand what the customer wants.. And give it to you”.
We are able to supply all types of aluminium
extrusions and precision machined aluminium components utilizing aluminium
profiles. Industries serviced, include – Automotive, Electronic,
Architectural, Building, Medical, among others. Products include special
aluminium extrusions, machined aluminium components, aluminium CNC
machining, aluminium tubes, aluminium angles, aluminium bars, aluminium
cutting, free issue aluminium machining, aluminium castings and aluminium
to various alloys including 6063, 6082, 6005.
We have our own in-house designer to ensure your
aluminium profiles can be made to your specifications. This will enable
you to have confidence that your design will be a cost-effective solution.
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| Figure 2. Designing aluminium
extrusions with improved stiffness. |
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