Making aluminium foil
Alufoil is a very thin sheet of aluminium ranging from about 0.006mm to the upper ISO defined limit of 0.2mm (200µm). It is produced by first rolling heated ingots (hot rolling) down to coils of thickness between 2 and 4mm. The coils are then successively cold rolled to the required foil thicknesses. A second foil rolling method, continuous casting, bypasses the ingot stage and converts molten metal directly into a thick strip which is immediately rolled into the coil from which the foil is then rolled.
To obtain the very thinnest foils, two layers are rolled simultaneously. This ‘double rolling’ results in the difference between the two surfaces – matt and polished – the matt side being the inner side during double rolling. The two layers of alufoil are then separated. The resulting large reels are slit to the widths needed for further processing for the required end use – flexible packaging, foil containers, lidding foils, household foil, heat exchanger foil, laminations for heat insulation materials, etc.