From Bauxite to Aluminium - The Production Process

From Bauxite to Aluminium - The Production Process Illustrated [299kb]

melted aluminium

In the earth's crust aluminium does not arise as pure aluminium but as a compound, e.g. as bauxite. Following oxygen (47.3%) and silicon (25.8%), aluminium is, with 8.1%, the third most common element and at the same time the most common metal in the earth’s crust. Extraction is done in two steps. Using the Bayer process, aluminium oxide is separated from the bauxite. This aluminium oxide is then split into aluminium and oxygen by electrolysis in aluminium smelters.aluminium slab

More than 2,000°C are necessary to melt down the freshly produced aluminium oxide. Already now the "recipe" is tailored to the final application. By the help of additives (magnesium, silicon, manganese, etc) different alloys are created which later form the mechanical properties. Therefore, processing possibilities for the customer can be established at a very early stage.

The weight of six elephants

The melted mass is cast into ingot form. Such an ingot can be 9 m long and weigh in excess of 30 t - the weight of six elephants. Precise milling techniques provide an excellent surface. By means of annealing, the ingot is then made ready for hot-rolling: It can be heated to a maximum of 550°C to be cold-rolled later down to as little as 0.2 mm thickness. A coil may be up to 2.7 m wide and weigh up to 20 t. These production steps are crucial for the ultimate quality.

aluminium coil

And very fast

By means of rolling speeds up to 480 metres per minutes, a part processed coil is created – although its surface is still untreated, it already has the excellent properties of rolled aluminium. Along with excellent processing possibilities as well as recyclability, its formability, deep-drawing, edging, and renowned light weight characteristics make it unique.

Worldwide production of primary aluminium

Total for 2009 to 2014: 223, 336 thousand metric tonnes

 

 

worldwide primary aluminium production

 

Acknowledgements
Many thanks to Novelis and the International Aluminium Institute for allowing the use of this information.