Aluminium

Of the five metals that now show the highest figures for annual tonnage production in the world, three (iron, copper, and lead) have been known and used by man for many thousands of years. The fourth (zinc) did not come into general use until the Middle Ages. Only the fifth (aluminium) is of ultramodern origin, as far as mankind is concerned. Discovered in 1825, and first publicly exhibited at the Paris Exposition in 1855, aluminium was still so difficult to obtain that it was more expensive than silver, until the development of the dynamo provided cheap electricity and the development of the present electrolytic process for its production made it possible to make large quantities cheaply. Even today, the world production of aluminium is only about one per cent of the world production of iron, although about half that of copper by weight.

The fundamental properties upon which the usefulness of aluminium depends are its lightness, workability, resistance to corrosion, high electrical and thermal conductivity, silvery luster, and high power of reflecting light and radiant heat. With these, there must, of course, be combined a strength adequate for the purpose; and since pure aluminium is not very strong (as compared with iron, for example), the development of the required strength with a minimum reduction in its other desired properties has been a basic problem of the fabricating industry. Since, when the metal was new, the established metal-working industry was broadly content with the metals and practices available to it, and disinclined to spend money in developing a new and untried metal, the whole burden of both technological and commercial development had to be shouldered by the producers of the metal, in order to sell their product, and they became fabricators as well as producers.

Дата добавления: 2015-07-20