May 2013 Tube ProducTs InTernaTIonal
59
Aluminium for every application
By Mark Jennings, Dawson Shanahan Ltd
Surface finish can also be precisely controlled with cold
forming, achieving results that other processes could only
achieve at far greater cost. Pre-forming steps may be
required because, owing to the lack of heat, formability is
low, and annealing and high forming pressures may also be
necessary during the process. However, cold forming can still
offer a significantly faster process option than die-casting or
machining from solid aluminium.
Where lower cost components are concerned, the statistics
for cold forming are particularly impressive: parts can be
produced at rates of up to 300 per minute, compared to
more expensive and time-consuming machining processes.
Manufacturers can also consider employing a combination
of cold forming and machining, again making significant
savings.
Though it is clear that time and money can be saved by cold
forming, this method is far more than simply an economy
option. Cold forming is also capable of producing parts that
are stronger than machined components.
T
he malleability, lightness and abundance of
aluminium have ensured its popularity within
engineering, while its resistance to corrosion and
conductivity have only contributed to that success.
The additional fact that aluminium can be economically
recycled to retain 100 per cent of its natural qualities
makes it a suitable metal to employ as we all strive for
sustainability, so it is important to consider the range of
processes that can be applied to aluminium in order to
bring specific benefits to many different applications.
The malleability, lightness
and abundance of aluminium
have ensured its popularity
within engineering
The three most common methods of processing aluminium
are machining, forming and, the most widespread of all,
rolling. Aluminium is rolled by passing an ingot of the metal
through a hot rolling mill. It is then cooled before being
subjected to the same process several times until reduced to
a thickness of between 4 and 6mm. The aluminium can then
be cold rolled to a thickness of as little as 0.05mm.
50 per cent of the world’s aluminium is rolled, largely for the
packaging of everyday disposable items such as canned
beverages, but rolled aluminium can also be subjected to
secondary processes for use in more demanding applications,
such as supersonic aircraft, where heat-treated aluminium
can withstand extremely high temperatures. Strain-hardening
alloys can be used in pressure vessels, cryogenic tanks,
rail carriages and so on, while heat-treatable alloys provide
material for the construction of missiles and armour plating.
Machining, in which a cutting tool removes chips of metal to
achieve precise dimensions, is another familiar process used
in the industry for shaping manufactured aluminium. The
aeronautical and automotive industries have made good use
of this fine precision technique; the machining of parts for the
aeronautical industry can result in the removal of 95 per cent
of the volume present, leaving behind a light but resilient part
tooled from the remaining 5 per cent.
The third method of machining aluminium is forming, an
entirely different way of processing manufactured aluminium
not always thoroughly considered by engineers and which,
therefore, needs to be explored in a little more depth than
rolling or machining.
There are two distinct forming processes: hot forming and
cold forming. A more complex shape can be forged from
parts of greater weight and volume using hot forming, but
the high temperatures required make a correspondingly high
demand on energy. Cold forming offers a strong, economical
alternative if, for instance, the complexity offered by hot
forming is unnecessary.
