I. Natural Quality of Aluminum

Aluminum is a kind of light metal with its compound widely distributed in the natural world. The aluminum resource in the earth's crust is about 40 to 50 billion tons, ranking the third by being next to only oxygen and silicon. In metal categories, it ranks only second to steel, being the second major category of metal. With special chemical and physical properties, aluminum is not only of light weight and hard texture, but also of good ductility, conductivity, thermal conductivity, heat resistance and nuclear radiation resisting property. It is an important basic raw material in national economic development.

Aluminum has specific gravity of 2.7 and density of 2.72g/cm3 which is about 1/3 of common metal. The mechanical property of commercial-purity aluminium is relevant to purity, as well as processing status of material. As aluminium is of good plasticity and ductility, it is convenient for various cold and thermal pressure processing. It can be fabricated as aluminum foil with thickness of only 0.006 mm, as well as very fine cold-drawn wire. Aluminium can be fabricated as alloy and hardened by adding other elements. The strength can even exceed that of structural steel, while maintaining the advantage of light weight.

Production of aluminium ingot consists of production processes of bauxite exploitation, aluminium oxide production and aluminium electrolysis.

There are mainly three types of bauxite being used to produce aluminium oxide: gibbsite, diaspore and boehmite. Among the proven global reserves of bauxite, 92 % of them are weathered lateritic bauxite, belonging to the type of gibbsite. This kind of bauxite features low silicon content, high ferric content and high alumina-silica ratio. It distributes in a relatively centralized manner at western Africa, Oceania and Central and South America. The rest 8 % of bauxite is sedimentary bauxite, belonging to boehmite and diaspore types of middle-low grade. It mainly distributes at Greece, the Socialist Federal Republic of Yugoslavia and Hungary. As the three kinds of bauxite are of different characteristics, various manufacturers adopt different production processes in production. There is only Bayer process, lime - soda sintering process and Bayer and sintering combined process available. Generally, Bayer process is employed for production of bauxite of high grade, while combined process or sintering process is employed for bauxite of middle-low grade. With the advantages of simple process and low energy consumption, Bayer process has become the major method in current aluminium oxide production. The output with Bayer process accounts for about 95 % of the total production of aluminium oxide around the world.

Aluminium electrolysis production can be divided into three categories including self-baking cell with side-mounted anode bar, self-baking cell with top-mounted anode bar and pre-baking anode cell. The technology of producing electrolytic aluminium with self-baking cell features simple equipment, short construction cycle and small investment. However, it has disadvantages, such as difficulty in handling the exhaust gas, severe pollution, difficulty in mechanization, great labor intensity, difficulty in enlargement and low production of single cell. This production technology is now being eliminated. At present, most countries and manufacturing enterprises in the world are employing large pre-baking cells. The cell has current intensity up to more than 350KA. It is of high degree of automation, low energy consumption, high single cell production and meets the requirements of environmental protection laws and regulations.

II. Classification of Aluminum and Aluminum Products

1. Production process of electrolytic aluminium: bauxite→aluminium oxide→electrolytic aluminium.

2. According to contents of principal components, aluminium ingot can be divided into three categories: high grade pure aluminium (with aluminium content of 99.93%-99.999%), commercial high-purity aluminium (with aluminium content of 99.85%-99.90%) and commercial-purity aluminium (with aluminium content of 98.0%-99.7%).

3. According to forms of market products, aluminium ingot can be divided into three categories: one is production products, such as plate, tape, foil, tube, rod, forge piece and powder; one is cast aluminium alloy, wire rod, wire pole and cables; one is various aluminium products in daily life.