General
-
Foil
is a very thin sheet of rolled aluminium supplied in its pure form
(‘commercial purity’) or in a variety of alloys and tempers which
give a wide choice of tensile properties.
-
The
thickness of foil ranges from the thinnest currently produced
commercially at about 0.0065 mm (or 6.5 µm) to the defined upper
limit of 0.2 mm (or 200 µm). Material thicker than 0.2 mm is defined
as sheet or strip.
Manufacturing
Process
- Aluminium foil is
produced by rolling sheet ingots cast from molten aluminium then
re-rolling on sheet and foil rolling mills to the desired thickness,
or by continuously casting and cold rolling. The continuous casting
method is much less energy intensive and has become the preferred
process . For thicknesses below 0.025 mm (0.01 in), two layers are
usually put together for the final pass which produces foil with one
bright side and one matte side. The two sides in contact with each
other are matte and the exterior sides become bright. This done to
reduce tearing, increase production rates and to help control
thickness.
Applications
- Aluminium foil
laminates are also used to package many other oxygen or moisture
sensitive foods, in the form of pouches, sachets and tubes, and as
tamper evident closures. Aluminium foil containers and trays are used
to bake pies and to pack takeaway meals, ready snacks and long life
pet foods. Aluminium foil is also widely used for thermal insulation
(barrier and reflectivity), heat exchangers (heat conduction) and
cable liners (barrier and electrical conductivity).
- Heavier foils made
of aluminium are used for art, decoration, and crafts, especially in
bright metallic colours. Metallic aluminium, normally silvery in
colour, can be made to take on other colours through anodization.
Anodizing creates an oxide layer on the aluminium surface that can
accept coloured dyes or metallic salts, depending on the process used.
In this way, aluminium is used to create an inexpensive gold foil that
actually contains no gold, and many other bright metallic colours.
These foils are sometimes used in distinctive packaging.
Market
- India has large
resources of high grade bauxite (the basic alumina ore) deposits
placing it fifth in the world after Australia, Guinea, Brazil and
Jamaica. Major bauxite reserves are concentrated on the East Coast
along Orissa and Andhra Pradesh. Today, India's per capita consumption
of aluminium is below 1 kg. And while globally there are about 3,000
applications of aluminium, India has only around 300.The capacity for
producing aluminium has increased consistently over the past few years
and is now six lakh tonnes a year.
- International
metal prices are quoting around $1,400-1,500 a tonne. The slowdown in
Chinese demand and lower consumption by western world smelters has
kept alumina prices depressed, currently hovering below $135 a tonne.
It is expected that prices of aluminium will stabilise around
$1,550-1,600 a tonne and in the long term rise to $1,750.
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