It is among the youngest metals – because it is among the last to be discovered by man – yet it is already used in every production sector: from electronics to food, from automotive to aerospace, from architecture to design, from pharmaceuticals to ‘engineering. Aluminum has even been chosen by research institutes to investigate particles. And we could go on and on.
100% recyclable, infinite times
Aluminum is defined as a “green” metal precisely for some aspects strictly connected to its intrinsic characteristics and the advantages that these entail: infinite recyclability, environmental protection, and an important contribution to the reduction of emissions into the atmosphere in line with the main sustainability objectives and protocols in defense of the climate.
The recycling process
Once collected, aluminum packaging and scrap are sorted, then pressed into bales and taken to the foundries. Here the material is pretreated to around 500 degrees to remove paints or other adhering substances. It is then melted at 700 degrees to reach the liquid state from which ingots, billets or plates ready to be processed by industry are obtained.
The production of 1 kg of secondary aluminum, or from recycling, has an energy requirement that is equivalent to only 5% of that necessary to produce 1 kg of metal from the mineral. Going even further into detail: to obtain 1 kg of aluminum from bauxite, 14 kWh are required, while to obtain 1 kg of aluminum from scrap, only 0.7 kWh of energy are needed. This process also saves on average 8 tons of CO2 per kg at each recycling. This energy saving has meant that about 50% of all raw aluminum produced in Western Europe comes from recovered and recycled material and that even in Italy the percentage reaches 100%.
Energy and Recycling
Plinus the Elder speaks for the first time about alums – salts with a double formula in which aluminum is normally present – in his work Naturalishistoria. The Latin naturalist writer also makes us aware of their uses: used both as a mordant to fix the colors of fabrics, and as a salt used in the embalming of men and animals, in the tanning of skins and to make wood fireproof.
The first supply problems – with all that ensued for European industries – date back to the mid-fifteenth century, when the Turks of Mohammed II conquered Asia.
The deposits discovered in the Tolfa Mountains represented an opportunity to compete with the “infidels” and Pope Pius II entrusted Giovanni da Castro with the production of alum, a product on which obviously a papal tax was charged.
The “papal” alum became so important that Paul III, who in the meantime succeeded his predecessor, imposed its use on all Europeans, under penalty of excommunication.
The trade in alum exercised such a strong economic power that the use of non-papal alum was excluded from the list of condonable sins for payment by the 1517 indulgence of Leo X, an episode that led Martin Luther to initiate the Protestant Reformation.
It was the English chemist Sir Humphrey Davy who was the first to hypothesize, in 1807, that aluminum was the salt of a still unknown metal and that – precisely because of its presence in alum – he called “aluminum”, later modified to “aluminum” .
Only 18 years later, in 1825, the Danish physicist Hans Cristian Ørsted obtained the first drops of pure aluminum by heating an amalgam of aluminum and potassium.
To continue his studies, one of his German disciples, Freidirich Wohler, who came to discover many properties. It was the discovery of the remarkable lightness of the metal that attracted the attention of the scientific and industrial world, so much so that considerable sums were allocated to continue the research.
In the mid-1800s, the French chemist Henri Sainte-Claire Deville was developing a process capable of producing limited quantities of aluminum for industrial purposes.
The complexity of the method, however, made the new metal even more expensive than gold.
Only in 1886, the American Charles Martin Hall and the Frenchman Paul Heroult discovered simultaneously, but independently, the electrolytic smelting process capable of obtaining metallic aluminum from alumina.
Hall-Herout is still the system used to produce aluminum, albeit refined by subsequent research.
The most important at an industrial level is that of the Austrian Karl Bayer who in 1888 patented the technique capable of extracting aluminum oxide from bauxite, the most important source of aluminum today for all modern industrial productions.
And if throughout the twentieth century aluminum was valued for its intrinsic characteristics such as ductility, lightness, heat conductivity and resistance over time, the new millennium has brought to light another aspect that has already allowed us to decree this metal as the element of the future. In fact, aluminum is infinite, and not only because it is the third most present metal on planet Earth, but because it can be recycled an infinite number of times.
Yes, because aluminum can be remelted over and over again without suffering quality losses. And the quantity of aluminum obtained through recycling in circulation is constantly increasing: with 51,400 tons of aluminum packaging recycled in 2019, equal to 70% of the total 73,400 tons placed on the market * Italy is confirmed in 2019 among the excellences in European level for the amount of recycled aluminum produced.
A secondary raw material that can be used as new: recycled aluminum does not suffer any loss of quality. Here, new profiles or other high quality products are born from the scrap, and new laminates are created from sheets in different aluminum alloys and aluminum sheets. Different high-quality products can be made from beverage cans. Today, 75% of all aluminum that has always been produced in the world is still in use.
Today aluminum is certainly the preferred material for the construction of any means of transport: two wheels – whether for road or racing – have found in metal a valid ally for aerodynamics and lightness. This last feature is also fundamental for the entire automotive electric market. Not to mention the hulls which, thanks to the new aluminum alloys, allow considerable fuel savings, thus also safeguarding our seas.
And with the spread of electronics and robotics, now present in everyone’s life, aluminum enriches one’s portfolio and becomes wearable “wearable”. Watches, glasses, headphones: hi-tech is all made of aluminum. And wanting to dwell on the theme, its non-toxic character and its flexibility, combined with the elegance of color, have led to numerous fashion houses starting to make jewelry and accessories with this metal.
due to its immediate oxidation in contact with the air which protects it from both water and the aggression of various chemical agents, it makes it widely used both in transport and in construction.
High electrical conductivity
then it makes it the most popular material for high voltage conductors.
with the same volume, aluminum weighs in fact about a third of copper and steel. Precisely for these reasons, for example, in modern airplanes the percentage of aluminum reaches about 80% (especially in transport ones). The automotive world has long used this material for different parts of the vehicle (or for the entire bodywork). But it is undoubtedly the decisive increase in the production of electric vehicles that favors the use of aluminum in the near future, and more generally that revolutionizes the world metal market.
The metal, in the liquid state, is obtained from alumina through the Hall-Hèroult electrolytic process which takes place at a temperature of about 950 ° C in a fluorinated bath crossed by a high intensity electric current.
From here, it undergoes further transformation processes that differ according to the intended use. Among them, the continuous and semi-continuous casting, from which wire rods are obtained and, through drawing, wires, plates, billets.
To reduce the thickness, on the other hand, lamination is used, which can take place both hot and cold, and which allows the production of aluminum sheets that can reach only 4 μ of thickness.
By extrusion, on the other hand, an aluminum billet, using a steel matrix, is transformed into a constant section profile. It is typically a process used to produce doors, windows, pipes, but also bodywork, aircraft and ship parts.
Forging, on the other hand, starts from a hot metal pad that is compressed in a mold and is used to make pieces up to 100 kg in weight. The combination of these two processes is called impact extrusion: for example, tubes for toothpastes, shaving creams, cosmetic products are made.
In the automotive industry, on the other hand, the casting technique is frequently used, in which molten aluminum is poured into molds to obtain pieces such as pumps, pistons, manifolds and many others.
A last process used industrially is that of drawing, with which the piece of aluminum is passed through a mold that gives it its final shape. This method produces in particular small gauge wires and tubes, used in the most diverse fields.