A BIT OF HISTORY...
Despite the fact that nowadays it is the 2nd important metal among the most used ones, aluminium has almost a short history, as it was discovered by a Danish man called Hans Christian Örsted in 1827. It was mainly the result of the fact that aluminium is not naturally pure found in nature, that is why it must be extracted from bauxite through chemical processes that were not known at that time.
Because of the difficulty to produce it on a large scale, in the early times, it was considered as a priceless metal to such an extend that Napoleon III used to give a royal welcome to his most important guest with aluminium cutlery instead of gold one.
The method to obtain prime aluminium from alumina (pure aluminium oxide) on an industrial scale was just discovered by two investigators in 1886. They were Paul Louis Toussaint Heroult (Normandy-France) and Charles Martin Hall (Ohio-United States). Both reached the same result without meeting each other and what it is really singular is that both of them were born and died in the same year.
Aluminium production can be separated into four stages:
- Bauxite Extraction
With a proportion of 8.13 %, aluminium is the 3rd more abundant metal in the earth surface.
In nature it is found as bauxite which is extracted from opencast mines.
Alumina (pure aluminium oxide) is taken from bauxite through a chemical process called Bayer, which consists of separating, through caustic soda, aluminium oxide from other substances present in bauxite. As a result of this process, alumina is taken and it has a thin white powder appearance.
Reduction to prime aluminium
Prime aluminium is taken by means of alumina reduction, according with the Halt-Heroult method, in electrolytic cells, which are crossed by a big current intensity. Pure or prime aluminium is taking away from cells at regular time intervals and from a continuos process.
Alloys and final format obtaining
Afterwards, liquid stated aluminium is carried to retention furnaces were metals like titanium, magnesium, and copper are added to prepare the customer's required alloys. Alloys are obtained in different ways: ingots, granulated material, extrusion bars and laminated sheets.
To produce 1 prime aluminium ton, 2 alumina tons (extracted from 4 tons bauxite) are used.
These are some of the advantages that make aluminium one of the most versatile and used metals.
It weights three times less than copper or steel, that's why it is used in transport, which saves energy and therefore it optimises the carrying capacity.
When it comes into contact with oxygen, a thin transparent cover that protects it from rust, is created. That's the reason to be used in home utensils and in the construction sector where its surface can also be treated through painting or anodising, which increases the resistant to be out in the open.
Excellent weight/resistance relation
Despite its low weight, aluminium has a high resistance when it is alloyed with other metals or tempered. Some aluminium alloys can be more resistant than standard steel.
Excellent heat conductor
It is three times more conductive than steel, therefore, it is used in cooking utensils, engine parts or in thermal disperses.
Good electrical conductor
Its conductivity is 60 % superior to the copper's one, but its weight relation makes it to be used as a conductor in high tension cables because of the long distances between towers that make necessary the use of low weight materials.
Excellent cryogenic properties
It increases its ductility under very low temperatures and it keeps its properties. On the contrary, steel becomes fragile and brittle.
Aluminium is also hygienic, therefore, it is used in food and medicine packing and packages. It is used in cooking utensils and containers for carrying food and drinks.
In opposition to steel, aluminium is not magnetic. This property is very useful in magnetic needles, compasses, aerials, electronic elements manufacture.
Its appearance doesn't spoil with time, that is why it is very useful in the construction sector, decorating and in elements where a modern and excellent finishing coat is needed.
This is an outstanding aluminium feature because through a very economical way, aluminium can be retrieved, saving energy and natural resources.
Aluminium has plenty of applications, therefore nowadays it is one of the most used metals. Some of them are mentioned here, according to the semi-manufactured products:
Sections - Pipes - Billets
They are mainly used in the construction sector (doors, windows, dividing structures, modular structures, decoration, draining, architecture, etc.). Nevertheless, they are also used in robotic, automation, electricity and lighting like heat dispersers, electronic equipment, coach and plane building, navigation, sport equipment, tools, toys, etc.
Sheets - Laminated
They are used in different applications like coachbuilding, car and plane's floors, roofs, façades, tanks, aerosol, tins, front parts and dashboards, instrument panels, furniture, numberplates, etc.
Through sheet stamping, it can be used to make cooking utensils, adornment, desk elements, video and audio casing, poster equipment, machine elements, drink's tins, etc.
They are produced in different thickness and flexibility grades. They are mainly used to pack food, drinks, medicine, chemical products, and all elements that must be protected from moist, light, or any external agent, making good use of the aluminium impermeability, opacity and hygiene.
Cables - Wires
They are generally used in high tension cables because of its low weight and conductivity. They are used in electronic signs wires and in heat transmission equipment for temperature measuring.
About 60 % of the aluminium used in the car industry comes from cast elements, now for engine parts, coachbuilding elements, now for tyres.
Because of the aluminium casting efficacy and the necessary low investment to do it, a big quantity of products are made under this system. Among them, we mention: adornment elements, applications and iron work elements for furniture, home electric appliances' parts, key rings, medals, desk elements, light devices, religious pieces, toys, etc.
Powder - Alumina
Powder aluminium or aluminium oxides have lots of applications. Among the most important ones we mention: deoxidant in iron and steel industry, mining explosive, substances used for swimming pool treatment, make-up, medicine, paintings and inks, fireproof elements, abrasive products, brake-lining, polishing paste, agrochemical products, etc...