The Hazelett aluminum strip casting process
EBNER.blog | David Hazelett, Hazelett, USA
The Hazelett aluminum strip casting process
Aluminum strip and sheet are manufactured from cast slabs or strip in either a charged process or a continuous casting process. Hazelett’s process of choice is continuous casting, in which a Hazelett twin-belt casting facility is used.
The image below shows the most important steps in the processing of aluminum to strip and sheet. Conventional direct chill (DC) casting is the first process shown, and the number of processing steps that this involves can easily be seen. They include preparation of the molten metal and alloying, DC casting, sawing, machining, preheating of the rolling ingots and hot rolling (both roughing and finishing). The hot rolled strip is then cold rolled to reach its final dimensions.
In comparison, the path taken in a continuous casting process is much shorter. Two continuous casting processes are important in the manufacture of aluminum strip and plate: twin-roll casting and twin-belt casting. In twin-roll casting, the processing steps include the preparation and alloying of the molten metal, casting and winding. The strip is then cold rolled and brought to its final dimensions. In twin-belt casting, casting is followed by in-line hot rolling to produce a hot-rolled strip that is thinner than the strip produced in a twin-roll casting process. This means that the amount of cold rolling that is subsequently required is reduced. Our twin-belt continuous casting process also requires significantly less space than conventional processes. Up to 20 twin-roll casters are needed to produce as much as a single Hazelett caster does, meaning that Hazelett equipment has the lowest space requirements of any facility.
The image below shows a typical Hazelett line, which starts with a melting/holding furnace and continues with metal treatment, casting, in line hot rolling and winding.
The majority of the Hazelett facilities built in North America during the 1980s and 90s were for scrap. The new millennium, however, saw both the rapid expansion of existing smelting plants and the construction of new ones, particularly in China. The focus thus shifted to Hazelett facilities that were built close to these plants and at which the molten metal could be transformed into sheet. Directly supplying a Hazelett line with metal from a potline is one of the most cost-efficient methods of adding value to molten metal.
However, as the construction of new melting facilities has slowed and awareness of the need to reduce energy consumption and ecological footprints has increased, there has been renewed interest in charging Hazelett lines with recycled scrap. Hazelett casting facilities are capable of producing a wider spectrum of alloys than twin-roll casters, making the Hazelett process particularly attractive for the recycling of post consumer scrap.
Together with MINO SpA, the members of the EBNER GROUP (Gautschi / GNA and Hazelett) offer fully integrated facilities for the continuous casting of aluminum strip – regardless of whether the project is based on the use of primary metal or recycled scrap.
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