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Aluminum is a chemical element with the symbol Al and atomic number 13. In the periodic table, the element belongs to the metals of the III main group, also known as the boron group, formerly called the group of earth metals. Aluminum is a silvery-white light metal. It is the third most abundant element and the most common metal in the Earth's crust. In 2010, about 41 million tons of primary aluminum were excavated and processed. Although it does not belong to the precious metals, it reacts with water from the air only superficially, building a protective passivating layer on the surface of the metal.
Since aluminum cannot be separated from aluminosilicates due to the manner and type of chemical bonds, the most economically justified and industrially efficient way of aluminum production is the processing of bauxite ore. A mixture of aluminum oxide and aluminum hydroxide is released from bauxite ore from foreign impurities such as iron oxides and silicon oxide, by the action of soda ash (Bayer process) and fried in rotary kilns to aluminum oxide (Al2O3).
Aluminum is a relatively soft and tough metal. The extraction resistance of pure aluminum is about 49 MPa, while in its alloys it is from 300 to 700 MPa. Its modulus of elasticity is, depending on the alloy, about 70,000 MPa. It is easy to pull out and can be processed into very thin foils by rolling. So-called aluminum crushed alloys can be well processed, bent, pressed and forged even at lower temperatures.
The specific weight of aluminum is about 2,698 kg / m³ .
Due to its low density, aluminum is often used in circumstances where it is necessary to reduce weight, for example in transport machines in order to reduce their weight and thus fuel consumption. This is especially true of spacecraft and airplanes. Apart from them, the importance of aluminum has also grown in the car industry. In the past, the automotive industry used little aluminum, because it was associated with problems of its high price, poor welding of aluminum parts as well as problematic resistance to material fatigue and deformation properties. As early as the 1930s, some American companies used aluminum to reduce the weight of military amphibious vehicles. When building small and medium yachts, the corrosion resistance of aluminum in salty seawater was highly valued,