Aluminium Technology (continued)

Improvements to composition and in particular, to rolling practice through innovative control systems, have made it possible for aluminium sheet with higher strength and more exacting tolerances to be produced. This has greatly assisted Australian can producers, for example, over the last eight years they have been able to obtain 30 per cent more cans from the same quantity of metal, a very significant productivity improvement. This was achieved through spin-necking and down-gauging, refinements that were supported by the development of new alloys and the advances in casting and rolling techniques.

Further technical improvements have been achieved in casting both into ingots and in the vertical direct chill casting operation where the most modern metal filtering system and degassing facilities are utilised. 'Airslip' casting for billets cast at the smelters can achieve the highest quality standards for extrusion billets.

In the extrusion division of the business, a new CADCAM computer system has been installed to enhance the quality and speed of tool and die manufacture resulting in considerable cost savings.

Basic research and development over some years had been directed towards improved foundry products and succeeded in developing a new wear resistant alloy, 3HA, which has a superior combination of properties which makes it attractive for demanding automotive applications. Comalco entered into a development agreement with Cosworth Group, UK, which has given the Company the capability to cast and test a wide range of 3HA automotive castings, including full engine blocks and cylinder heads.

In 1968 facilities for producing aluminium powder and paste were installed at Bell Bay; it was Australia's only powder blowing plant. The powder is produced by an air atomization technique which converts a stream of molten aluminium into microscopic particles of acicular shape. The blown powder is collected, sieved and packed for use by the military, for commercial explosives, Thermit welding and epoxy resin fillers. The paste is produced by a special ball milling technique using a white spirit carrier medium and is used in paints and anti-corrosive devices.

Alcan Australia have four principal fabricating plants with the largest that at Granville, where a complete range of mill products can be produced. They have a conventional two-high reversing hot mill and a four-high unidirectional cold mill which can roll down to 0.25 mm. Other production may be carried out on a 1270 mm wide Sendzimer reversing cold mill to give close tolerance sheet or coil down to 0.20 mm thick. Strip can be fabricated into tubing by seam welding which also enables a clad alloy to be used to improve corrosion resistance. For welding, modern Automatic TIG argon shrouded process is used without a filler wire; tube can range from 50 to 150 mm diameter.

Alcoa produce primary aluminium at its factories at Point Henry and at Portland, Victoria. Sheet ingots are cast, scarfed if necessary, heated and hot reduced on a continuous mill to about 4 mm thickness when it is coiled and cooled to room temperature. Further cold reduction and annealing may be carried out, sheet thicknesses range from 0.150 to 6.0 mm while foil down to 0.007 mm can be produced.

Australian Academy of Technological Sciences and Engineering