Primary aluminium (ingots, billets): properties and applications
Primary aluminium is a metal obtained by electrolytic reduction of alumina dissolved in molten cryolite. In commercial form, it is supplied as ingots, billets, wire rod, strip and other semi-finished products, which serve as the base feedstock for further processing into finished products. Due to its unique combination of lightness, strength, corrosion resistance, high electrical and thermal conductivity, primary aluminium occupies a strategic position in the global economy, supporting the development of aerospace, automotive, construction, electrical engineering and packaging industries.
Chemical Nature and Physicochemical Properties
Aluminium (Al) is a light silvery-white metal belonging to the group of light non-ferrous metals. Its atomic number is 13, atomic mass — 26.98 g/mol. The density of aluminium is about 2.7 g/cm³, which is approximately three times less than the density of steel, making it indispensable for vehicles where weight reduction is critical for fuel economy and payload capacity. The melting point of aluminium is 660 °C, and the boiling point is about 2500 °C.
Aluminium has high electrical and thermal conductivity. In terms of electrical conductivity, it is second only to silver, copper and gold, making it the main material for power cables and wires. The thermal conductivity of aluminium is also high, which is important for radiators and heat exchangers.
A key property of aluminium is its ability to form a dense oxide film (Al₂O₃) about 5–10 nm thick on its surface, which protects the metal from further oxidation and provides high corrosion resistance in atmospheric conditions and fresh water. This film also allows aluminium to be used in the food industry and for packaging production.
Aluminium is non-magnetic, non-toxic, has good ductility and is easily processed by pressure, casting, welding and machining. It also has high reflectivity, which is used in lighting technology and mirrors.
Classification, Grades and Standards
Depending on its chemical composition, primary aluminium is divided into high-purity and technical-purity aluminium. Requirements for primary aluminium grades in Russia and CIS countries are regulated by GOST 11069-2019 (formerly GOST 11069-2001), which applies to metal produced in liquid form, as ingots, billets, wire rod, strip and other semi-finished products.
High-purity aluminium includes grades A995, A99, A98, A97 and A95. In these grades, the content of the base metal ranges from 99.95% (for A95) to 99.995% (for A995). High-purity aluminium is used in the electronics industry, for the production of capacitors, special alloys and scientific research where minimal impurity levels are required.
Technical-purity aluminium includes grades A85, A8, A7, A7E, A7E, A6, A5E, A5, A35 and A0. The content of the base metal in them ranges from 99.00% (for A0) to 99.85% (for A85). Grades with the index "E" (A7E, A5E) are characterised by a reduced content of impurities that limit electrical conductivity and are used for the production of electrical wire rod. Grade A7E is distinguished by increased purity for certain elements and is used in critical electrical products.
For primary aluminium ingots, a separate standard GOST 11070-2019 applies, which establishes requirements for surface, packaging, marking, acceptance, testing, safety and transportation. Ingots are cast from primary aluminium of all grades and are intended for further remelting. For billets obtained by semi-continuous casting, standards also exist that regulate their geometry and surface quality.
Production Technology
Industrial production of primary aluminium is based on the Hall-Héroult process, developed in 1886 and still the only industrial method for producing the metal to this day. The essence of the process is the electrolytic reduction of alumina (Al₂O₃) dissolved in molten cryolite (Na₃AlF₆) with additives of aluminium and calcium fluorides.
Electrolysis is carried out in special cells (electrolysers) at a temperature of about 960 °C. A high-density direct electric current is passed through the melt, which reduces aluminium ions at the cathode, covered with carbon blocks. Oxygen is released at the carbon anodes and reacts with the anode carbon to form carbon dioxide (CO₂). Molten aluminium, being heavier, accumulates at the bottom of the cell and is periodically extracted using a vacuum ladle.
Aluminium production is energy-intensive: about 13–15 MWh of electricity is consumed per 1 tonne of metal. That is why aluminium smelters are traditionally located near sources of cheap hydroelectric power. The resulting liquid aluminium is cast into ingots, billets or sent for casting wire rod and other semi-finished products.
Applications
Metallurgy and steel deoxidation. Primary aluminium in ingots is widely used in ferrous metallurgy for deoxidising steel and binding oxygen, as well as for alloying special steels and alloys. Aluminium is also used for the production of ferroalloys and other master alloys.
Production of wrought alloys. Billets from primary aluminium serve as charge for producing wrought aluminium alloys (1xxx, 3xxx, 5xxx, 6xxx, 7xxx series), from which sheets, strips, profiles, pipes and rods are produced. These semi-finished products are used in construction (facades, window and door profiles, roofing systems), automotive (body panels, frames, heat exchangers), aerospace and packaging (beverage cans, foil).
Electrical engineering and cable industry. Due to its high electrical conductivity, primary aluminium (especially grades A7E, A5E) is used for the production of wire rod, from which power cables, power transmission line wires and winding wires are made. Aluminium is also used for the manufacture of busbars and current-carrying elements of electrical equipment.
Foundry production. Primary aluminium ingots are used to prepare cast aluminium alloys (e.g., silumins), from which machine parts, gearbox housings, cylinder blocks, wheel rims and other products for the automotive, aviation and instrument-making industries are cast.
Construction and infrastructure. Aluminium profiles and sheets are widely used for facade glazing, translucent structures, roofing systems, bridge railings and other building elements. Due to their corrosion resistance and durability, aluminium is the preferred material for critical construction projects.
Packaging and food industry. Aluminium foil and sheets are used for packaging food, beverages, medicines and cosmetics. Aluminium is non-toxic, does not absorb odours and provides barrier properties, extending the shelf life of products.
Other applications. Primary aluminium is used for the production of powders, granules, special alloys, as well as in nuclear energy, shipbuilding, consumer goods production and other industries.
Safety and Storage
Primary aluminium in ingot and billet form does not present a hazard when storage and transportation rules are observed. It is non-toxic, non-flammable and has no harmful effect on the environment. When handling ingots at long-term storage points, no special protective equipment is required.
The main precautions are related to the heavy weight of ingots and billets (the weight of one ingot can reach 20–25 kg, billets are significantly heavier), so lifting equipment must be used during loading and unloading operations and safety rules must be observed. During mechanical processing of aluminium (sawing, milling, grinding), fine chips and dust are generated, which can be fire-hazardous, so fire safety measures and effective ventilation are required.
Storage of ingots and billets is carried out on open areas with hard surfacing or in closed warehouses that protect the metal from moisture and contamination. Ingots are stacked in piles while maintaining stability. For long-term storage, protection from atmospheric precipitation is recommended, although aluminium has high corrosion resistance.
Market and Trends
The global market for aluminium ingots and billets demonstrates steady growth, driven by the development of the construction industry, automotive manufacturing and the packaging sector. Key demand drivers are the need for lightweight materials for vehicles, especially electric vehicles, where aluminium use is 20–30% higher than in internal combustion engine cars, as well as the growth of infrastructure construction in developing countries.
The Asia-Pacific region remains the largest producer and consumer of primary aluminium. Significant capacities are concentrated in China, India, the Middle East, Russia and North America. Key industry trends include the transition to low-carbon production (use of renewable energy, inert anodes), the development of closed-loop recycling and increasing requirements for traceability and carbon footprint of products. Producers with access to cheap electricity and modern technologies occupy stable competitive positions.
Conclusion
Primary aluminium in ingots and billets remains a fundamental feedstock of global metallurgy and industry. The unique combination of lightness, strength, corrosion resistance and high electrical conductivity makes it indispensable in aerospace, automotive, construction, electrical engineering and packaging industries. Electrolysis technology, despite its energy intensity, continues to improve towards reducing carbon footprint and increasing efficiency. Organising supplies of primary aluminium, including the selection of grade (A7, A8, A5E and others), supply form (ingots, billets, wire rod) and logistics, requires an individual approach that takes into account specific technological requirements and operating conditions.