The production of the primary aluminium is a recognisable marker of our company. This is not just the production; it is a story, an inspiration, a centre of our activity and the activity of our predecessors. It has been for more than 60 years. Since we belong among top-notch producers of the primary aluminium, we believe that the story of the aluminium in Kidričevo will continue with success.
The production of electrolytic aluminium
The production of electrolytic aluminium
Namely, at the end of 2007 we stopped producing aluminium in the electrolytic hall B, where aluminium had been produced since the very year 1963. Abolishment of the electrolysis B was a part of the production restructure, with which Talum switched to a new strategy of development. Without the electrolysis B the production in Talum was completely in accordance with ecological standards IPPC and with the Environmental Permit given by the Ministry of Agriculture and Environment, the Agency of the Republic of Slovenia for the Environment.
The electrolysis C
A centre-point operation of the electrolytic cell is built into in the electrolysis C, which is of high current intensity. The cells are operated by using modern mechanisation and automation. A process computer runs them. They are closed and connected with a system of accumulation and dry purifying of gasses.
Currently this is the latest technology developed by a French company Aluminium Pechiney.
The production process
The production process in the electrolysis C is almost completely automatized. Automatic regulation of the electrolytic cells is performed by a process control system, which is organised in two levels. The first operates with each individual cell; the second is for managing the complete electrolysis. Hence, each cell has its own microprocessor, which automatically regulates inter-electrode spacing, crust penetration, dosage of alumina and aluminium fluoride. All microprocessors are connected with a central computer, which carries out measuring and converting voltage and current in the electrolysis, alerting, data processing and saving.
To perform operations with the electrolytic cells in the electrolysis there are special multi-purpose lifts. All electrolytic cells are covered and connected to the purge of gasses through gas tank pipelines. Purifying of gasses proceeds with a dry process. Fresh alumina absorbs fluorine and then it is collected through baggy filters and transported into the process in the electrolytic furnaces. Efficiency of the system is extremely high, 97% at gasses collection and 99% at their purifying.
A production of anodes
What are anodes?
The anodes are positive electrodes by galvanic particles, electron tubes, semiconductor diodes, and electrolysis. The name comes from Greek and it means the way up, the way where electrons rise up out of the electrolyte solution.
We use them in the electrolytic cells in the process of the aluminium production.
What are cathodes?
The cathodes are negative electrodes by galvanic particles, electron tubes, semiconductor diodes, and electrolysis, where a chemical reaction of reduction proceeds.
We use them as a cathode bottom in the electrolytic cell during the electrolytic production of aluminium from alumina.
How does the production process proceed?
The production process is divided into the following phases:
1. The production of the green anodes
The production of the green anodes is based on:
2. Baking the green anodes
We bake the green anode blocks in a calcining furnace at the temperature of 1200°C. By baking, we improve solidity and electric conductivity.
3. The construction of anode sets
Before the use in the electrolysis, we construct the baked anodes in the anode set with an anode girder. Thus, we get filled anode sets, which are then used in the electrolytic process of the aluminium production.
4. The construction of cathode sets
We buy the cathode blocks as a final product. By using grey cast, we fill the blocks’ steel current conductors and construct them in the cathode set.
Aluminium never turns into waste
In comparison with the first production, only five percent of that energy is used to recycle the aluminium. The first production is expensive and energy consuming, but once the aluminium starts its life cycle, it does not get out of it anymore. Therefore, aluminium is considered as green metal since all of it being ever produced can be repeatedly used for centuries and it never turns into waste.
Due to their characteristics, cast alloys enable the use of large-scale casting procedures (pressure casting and casting in moulds) with high productivity. We produce them in the form of cast ingots and mould cast ingots.
- automotive industry (rims, bodywork, motor parts, chassis parts),
- aeronautical industry,
- shipping industry,
- civil engineering,
- food industry.
The characteristics of cast alloys are low specific weight, good corrosive resistance, good workability, clear and smooth surface and non-magnetic properties. We produce all main types of cast alloys. As alloy elements mostly silicon, copper, magnesium, zinc and manganese are used.Cast alloys by chemical composition - PDF
Dimensions - PDF
Preparation and treatment of melt for cast alloys
In the reverberating furnace hard aluminium is melted. The energy sources are natural gas and the warmth of aluminium, produced through electrolysis and heated up to 900 °C, which is derived with special pots from the electrolysis and transferred into the reverberating furnace. In accordance with the chemical composition of the alloy, alloy elements are added.
To decrease the sodium content or the content of other undesirable elements, salts are added, while a homogeneous chemical composition is achieved by mixing the melt.
The treatment of the melt is continuing during the casting process. To decrease the content of hydrogen a flow-through filter is used, which is connected through the oven with a groove. In the flow-through filter the inert gas argon is blown into the run in melt through special stirrers. Argon forms very small gas bubbles, which rise towards the surface of the melt and capture hydrogen and other undesired impurities.
The melt is continues its way from the flow-through filter through a ceramic filter in which inclusions are extracted (oxides, borides, carbides, fluorides, chlorides...).
In a launder, modifiers are added in the melt (wire AlTiB), which during the coagulation of aluminium positively affect the growth of crystal grains and improve mechanical characteristics of cast alloys.
Casting procedure of cast alloys
Continuous casting - casting of continuous cast ingots
The melt is transported through the system of launders to the distribution groove, where the moulds for continuous casting can be found. The set includes three moulds with eight castings per each mould, which enables the casting of 24 continuous cast ingots at once. Moulds are cooled down with cooling water from a closed cooling system.
The continuous cast ingots are sawn to precisely determined lengths. They are piled with an automatic forklift and bonded into a compact band.
Mould cast - casting of mould cast ingots
The melt is transported through the system of launders to the casting machine for mould cast ingots, where individual moulds are being filled with a casting wheel on an endless casting belt. These moulds are cooled down with cooling water from a closed cooling water system. Behind the casting machine is an integrated air refrigerator in which the mould cast ingots are cooled to ambient temperature.
Mould cast ingots are piled with an automatic forklift and bonded into a compact band.
According to the definition in the Dictionary of the standard Slovenian language a billet is a long, level object, generally round in its section. An aluminium billet is an intermediate product for the industry, which produces a wide range of products, mainly aluminium profiles, with various processes of plastic transformation (mostly with extrusion and forging).
- transport industry,
- vehicle industry,
- civil engineering,
- furniture industry,
- heat engineering.
We produce alloy groups series 6000, in which magnesium and silicon are the main additives. The most frequent alloys are:
- 6060 - alloy AlMgSi0,5
- 6005 - alloy AlMgSi0,7
- 6082 - alloy AlMgSi1
Casting of billets
For the production of billets modern technology is used, which provides the optimal metallographic transformation structure and a low hydrogen content.
The casting procedure is performed on a semi-continuous vertical casting machine in accordance with the "hot top gas slip" technology.
The most important element of the casting machine is a casting table with moulds for production of different diameter billets. During casting the casting table moves towards the bottom of an 8 meters deep casting cave, while the billets coming out of the mould are sprayed with a strong splash of cooling water and therefore cooled down
The load, which weighs up to 50 tons is moved with the help of a hydraulic cylinder. A precise vertical guidance and the assurance of a steady casting speed is provided by a process computer, which receives required data from an integrated very precise measuring equipment.
After the casting is completed the 7.5m long billets are pulled out of the casting cave with a bridge crane and are transported to the stabling table of the homogenisation oven.
Homogenisation of billets
After the casting, the billets need to be thermally treated to ensure optimal mechanical characteristics for further processing (extrusion of billets).
The thermal treatment is performed in a homogenisation oven, where billets are gradually heated and undergo homogenisation with a temperature of 535 °C to 585 °C. Billets are then forwarded to the air fridge, where high temperature gradients in the cooling of billets are achieved by means of turbo cooling.
The homogenisation oven is a closed chamber heated with natural gas. The billets are moved into differently heated temperature zones by a stepping transporter, that moves the billets into the next oven position in determined time intervals.
The correct heating and cooling process of different types of alloys is controlled by the process computer.
The cooled billets are sawed on both ends and the automatic forklift lays them on wooden bedding and binds them with straps into bands ready for transport.
The purpose of homogenisation:
- the transformation of needle form phase ß-AlFeSi into α-AlFeSi phase, that is easier to transform;
- decreasing of micro-segregation after the casting of billets;
- decreasing of tension in the material;
- controlled distribution of disperoids in alloys, which contain manganese, chromium and zirconium;
- during coolong, a minimum number of extracted intermetal phase Mg2Si according to crystal limits should occur, or a fine forced melted phase Mg2Si should be achieved.
We also produce wide strip, which is partially used for the production of evaporators.
- Maximum possible capacity: 8,000 tons per year
- Maximum possible width: 1,320 mm
- Thickness: 5 to 10 mm