ALLOYS

CAST ALLOYS

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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.

Use:

• 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.

BILLETS

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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).

Use:

• transport industry,
• vehicle industry,
• civil engineering,
• furniture industry,
• heat engineering.

Alloy types

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

Chemical composition of the chosen alloys for billets - PDF

Dimensions and characteristics - PDF

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.

WIDE STRIP

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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