- 21 November 2024
Aluminum was discovered only 150 years ago, but is widely used for industrial, military and consumer purposes. Aluminum-based alloys are used to make lightweight structures, as power conductors, food packaging and finishing materials. Let's take a look at how aluminum is produced and how to decipher its designations.
Due to its high affinity for oxygen, carbon reduction, in the case of aluminum, is impossible. Therefore, a process consisting of the following steps is used in the production of aluminum:
- Refining from bauxite: aluminum oxide is crushed, dried and evaporated to remove impurities.
- Dissolution of Al₂O₃ oxide in molten Na₃AIF₆ cryolite at 950 C⁰.
- Electrolysis of the alloy, in which the bond with oxygen is broken.
To give aluminum additional properties, the alloy is combined with titanium, zinc, manganese, chromium, nickel and other elements. Depending on the content of pure metal, impurities and alloying elements, different grades of aluminum are defined. In turn, the table of aluminum alloys is international and universal.
The table of aluminum alloys and purity index determines the physical and chemical properties of the alloy and indicates the use of the metal in certain industries. How, then, to distinguish aluminum grades? The table by purity looks as follows:
- Special: 99.999% - designation A999. For semiconductor production and laboratory work.
- High aluminum content: 99.95 -99.995% - A95, A97, A99, A995. Production of parts for radio and electrical equipment.
- Technical: 99-99.85% - A0, A5, A6, A7, A8, A85. For wires, gaskets and alloy preparation.
The modern international classification of deformable aluminum alloys was introduced in 1954, according to which each alloy is assigned a 4-digit "number".
So how do you classify aluminum grades? The properties of the metal are the key element of division here. Aluminum grades are divided as follows.
- The first digit indicates the main alloying element, which forms a series (group) of alloys with similar properties.
- The last two digits are assigned to the next digit in this alloy series.
- The second digit indicates the modification of the alloy. For example, Alloy 6463 Alloy modification is 6063 with slightly stiffer restrictions on the content of certain alloying elements and impurities, such as iron, manganese and chromium, in order to achieve a better final surface finish, for example during anodizing.
- The international standard ISO 209-1 and the European standard EN 573 include, also, an additional "chemical" designation.
This is how technical aluminum grades are designated. The properties of this type of alloys make them mainly used in the manufacture of chemical equipment and electrical conductors. This series denotes alloys with an aluminum content of not less than 99%. The designations are given according to the degree of purity of the aluminum and the type of impurities, the most important of which are iron and silicon.
The table of aluminum alloys also includes aluminum grades with copper admixtures. The main alloying element in this series is copper. This alloy has high strength, but reduced corrosion resistance. These alloys were among the first dural aluminum alloys and were given their name. Alloy 2024 is probably the best known and most widely used alloy in the aerospace industry.
Manganese is the main alloying element of the 3xxx series, increasing the strength of aluminum by about 20%. The corrosion resistance and workability of these alloys is very high. The most popular alloy of the series - 3003. Alloys of this series are often used in the construction industry, for appliances, roofing and facades of buildings.
This is a rather exotic alloy series, whose main alloying element is silicon. Copper, magnesium and beryllium can be found as additional alloying elements. Silicon content can be as high as 13.5% to lower the melting point and improve performance. This is very important, since most of these alloys are used to produce wire and rod for welding and brazing.
In the 5xxx series alloys, magnesium is the main alloying component. The results are strong, corrosion-resistant and well-weldable aluminum alloys. These alloys are used in the manufacture of ship hulls and other marine equipment, wire and welded tanks.
Alloys of this series contain magnesium and silicon in proportions of 0.2 to 1.8%, forming magnesium silicide, Mg 2 Si. These alloys have a good balance of corrosion resistance and strength.
The main alloying element in this series of alloys is zinc. The 7xxx series includes two types of alloys:
- Al - Zn - M g alloys, such as alloy 7005.
- Al - Zn - Mg - Cu alloys, such as alloy 7075.
This series includes newly developed alloys whose main alloying elements differ from elements of other series or for other reasons cannot be included in the "traditional" series.
