Aluminium – a very common element
Aluminium makes up approximately 8% of the Earth’s crust. After oxygen and silicon, it is the most abundant element. Aluminium is extracted from bauxite, a mineral quarried from open cast mines that litter the area around the equator. The foremost producers of aluminium are located in Brazil, Jamaica and Papua New Guinea. The largest European deposits are found in Hungary and the Balkans. Sweden has no bauxite deposits.
Refineries are located in close proximity to the mines, where aluminium oxide (alumina) is extracted from the raw bauxite. The alumina is then shipped to primary refineries where pure aluminium is extracted.
Use of aluminium has increased dramatically over the past 50 years. The European aluminium industry employs somewhere in the region of 200,000 people and has an annual turnover of approximately € 25 billion.
Aluminium is a highly malleable material. It can be alloyed with other substances to achieve the same level of durability as many types of structural steel. The metal is easy to work and can be welded, soldered or glued. The primary production process requires a considerable amount of energy. However, aluminium can be easily recycled using very little energy whilst retaining its intrinsic characteristics. The scrap aluminium industry is currently very buoyant, with a high level of collection being achieved throughout the world. For example, 90 % of all aluminium used in cars is recycled.
Low weight, a long lifespan and minimal maintenance requirements make aluminium a good environmental choice in respect of the life cycle of a product.
Extrusions pressed through matrix
Aluminium can be pressed, cast and rolled into sheets. Extrusions are made by pressing a heated aluminium ingot under force through a tool known as a matrix. The hole in the matrix determines the shape of the extrusion. Both solid and hollow extrusions can be pressed in this way.
Because aluminium is so maleable, many different functions can be built into extrusions. This contributes to simplified processing and installation and increases use scope.
Extrusions are adapted to meet the needs of each customer, product and area of use. There are an infinite number of designs available, and the choice of aluminium alloy affords extrusions different characteristics.
The cost of producing tools is relatively low and set-up times are relatively short. Because of this, power pressing also enables extrusions and products to be manufactured in short series.
Good characteristics lead to increased use
Aluminium extrusions are used in many industries. In the construction industry, they are used in windows, doors, foyers and balconies. This is due in no small part to aluminium’s ability to withstand corrosion and its low weight. This high level of durability is also a contributing factor in aluminium being a widely used material in weight-bearing structures in aircraft. In addition, aluminium’s heat conducting characteristics are exploited in solar panel design.
Aluminium extrusions are being increasingly used in the automotive industry, not least because of their light weight, which means fuel savings can be achieved throughout the life of a vehicle. Lighter trucks, buses and trains can be used to increase load capacity. Lighter vehicles also reduce the risk of injury in the event of a road traffic accident.
Aluminium has become an important design feature in many contexts, e.g. vehicles. Aluminium wheel rims are used both to emphasise the appearance of a car and to improve its driving characteristics.
In ship design, steel is being increasingly replaced by aluminium. This is particularly evident in the new breed of high-speed catamarans, which use aluminium extrusions and sheet aluminium. The low weight and minimal maintenance requirement means that more and more ships are being built in aluminium.
Weight is also a determining factor in aluminium’s popularity in the aviation and aerospace industries.
In the electronics and telecoms industry, extrusions are used in base stations, antenna attachments and front panels. The low weight and ability to incorporate a variety of functions are prime examples of why aluminium extrusions are used in components for the telecoms industry.
One kilogram of aluminium can conduct twice as much electricity as the same amount of copper. As a result, aluminium has largely replaced copper in high voltage cabling.
Compared to other metals such as iron, copper and lead, aluminium only has a brief history of use. Danish physicist Hans Christian Ørstedt was the first to successfully produce aluminium metal in 1824. Research into aluminium continued throughout the 19th century. At the World Exhibition held in Paris in 1889, a piece of aluminium with a degree of purity of 96% formed one of the exhibits.
Initially, aluminium was an exclusive metal, used extensively in jewellery. Later, its practical qualities came to the fore. Only after World War Two did the modern aluminium industry we recognise develop and has experienced rapid growth ever since.
Aluminium in brief
Aluminium has a density of 2.7 kilograms per cubic metre. Iron is approximately three times heavier.
Aluminium has a high conductivity for both electricity and heat, approximately 60% compared to electrolytic copper. If brought into contact with atmospheric oxygen, aluminium forms a protective oxide layer. If the layer is damaged, it simply re-forms.
Aluminium alloys have breaking strengths of between 70 and 700 Mpa. In addition, aluminium also maintains its ductility at temperatures down to -200 degrees and has a relatively large linear expansion coefficient.
(Source: Aluminium SIS handbook 12:2001)