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How Aluminium is made

Bauxite is mined by various processes. Once mined it is finely crushed for refining and recovery of alumina, the base from which aluminium is made. The separation of the alumina from bauxite is a complicated process. This involves the use of a caustic soda solution heated under pressure to dissolve the alumina. Impurities are filtered out of the solution in the form of a mud-like material. The filtered solution is cooled and alumina is recovered by precipitation in a hydrate form. The resulting fine crystals are then heated in long revolving kilns to drive off the water of crystallisation.

The product is alumina in a white powder form. Aluminium metal is produced in large steel shells lined with carbon. These shells are known in the industry as pots and are arranged in long rows called pot lines. Alumina is mixed with cryolite in the pots and large quantities of electricity are introduced to reduce the alumina into aluminium and oxygen. The process is continuous and molten metal is siphoned from the pots at regular intervals.

How Aluminium is turned into products

Once aluminium is produced it can be made into forms ready for manufacturers to convert into finished products. Industries requiring aluminium may specify from a range of alloys and their metal can be supplied in the form of ingots, extruded shapes, rod, tube, bar, sheet, plate and foil.

One of the best known forms of aluminum is sheet, which has many applications.The process starts with special alloy rolling ingots. These are pre-heated to rolling temperature, then fed into a hot mill with the ingot being passed back and forth through the mill. The process results in plate, with thinner sheets being formed by further passes between rolls under extreme pressure. it becomes longer and thinner in the direction in which the plate or sheet is moving.

Perhaps the most remarkable of all these forms is foil, which is aluminium metal that has been rolled very thin so that it is pliable yet strong. Aluminium foil is widely used in kitchens and food packaging.

Aluminium extrusions have been used commercially for many years. The process involves a heated billet being pushed under tremendous pressure through a die, the metal taking the shape of the holes in the die. Extrusions are mostly used to reduce the weight or number of parts in an assembly, or to achieve shapes that cannot be produced satisfactorily any other way.

The uses of Aluminium

The characteristics of aluminium combine to make aluminium a most versatile material for a host of applications.

  • Window frames
  • Door frames
  • Joinery fittings
  • Roofing
  • Gutters
  • Spouting
  • Wall cladding
  • Foil insulation
  • Roller doors
  • Insect screens
  • Venetian blinds
  • Awnings, louvres
  • Fencing
  • Balustrading
  • Flag poles
  • Kitchen utensils
  • Kitchen whiteware
  • Laundry whiteware
  • Air conditioners
  • Tubular furniture
  • Electric fittings
  • Light fittings
  • Household appliances
  • Food containers
  • Wrapping foil
  • Cans and closures
  • Computer parts
  • Sports equipment
  • Leisure furniture
  • Security grilles
  • Vehicle engines
  • Aircraft engines
  • Outboard motors
  • Motor mowers
  • Airframes and skins
  • Vehicle trim
  • Truck canopies
  • Coach bodies
  • Railcar bodies
  • Caravan bodies
  • Boats hull and trim
  • Transport containers
  • TV receiver aerials
  • Partition systems
  • Tanks and piping
  • Tubing and ducting
  • Reflector paneling
  • Armature windings
  • Wiring and cabling
  • Treadplate
  • Wall framing
  • Office furniture
  • Office equipment
  • Decorative ceilings
  • High-rise mullions
  • Sign frames, panels
Australia
Ullrich Aluminium Australian Aluminium Council Ltd