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Aluminium foil is produced first by rolling heated direct chill (DC) cast
ingots called hot rolling down to thicknesses around 4mm. This coiled product
is then cold rolled in a sheet rolling operation to foil stock. This reroll
stock which is a semi-finished rolled product of rectangular cross section is |
coiled form is suitable for further cold rolling at the Foil Mill. Another
method of production developed in the last number of years for production of
high quality sheet and foil products is by continuous casting. This process
bypasses the ingot stage and directly converts the molten aluminium into thick
strip which is then immediately rolled into coil from which foil can be
produced.
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To obtain foil in final thickness below 0.040mm two layers from the coils are
rolled simultaneously. The rolling of the doubled foil results in one of the
rolled surfaces on the outside of the doubled coil being bright and the inside
being matt or mill finish. After the doubled coil is rolled to gauge it is sent
to a separating machine and the two layers are separated into two single layers
of foil material for sending to the customer.
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After the completion of rolling the metal may be heated in a large
industrial furnace to obtain an annealed 0 temper or partial annealed temper
such -H22. The particular temperature used for annealing or partial annealing
will be dependent on the aluminium alloy and if any special quality features
are required such as improved wettability on the surface for subsequent
laminating and/or printing at the customers.
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| In the case of foil that will be used for containers a special food
grade approved lubricant (texturing) is applied during the slitting operation
to facilitate the container forming operation at the customer's plant. |
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