Metals in perspective

Man has always tried to improve his standard of living by changing his surroundings and by making tools to simplify the everyday tasks necessary for his existence. At first, the only materials he could use were those he could see around him - stone, wood and so on. He survived in competition with other animals because of his abilities with his hands and their co-ordination with his brain. Because he did not have the strength and speed of some animals, his survival depended on his skilful use of tools to get food and to keep him warm and safe.

Since the Stone Age, man has found many more materials that he can work with to his advantage. His ingenuity has led him to discover the potential of many natural products. However, the materials that helped him most to develop were the metals. Their characteristics of strength coupled with the ease with which they can be shaped made metals of vital importance in the technology of the past. The exploitation of other properties, such as electrical and thermal conductivity, made it possible to develop high technologies appropriate to the fields of space travel, communications and nuclear engineering.

The first metals which man discovered were copper and gold, because they occur naturally in the pure state. They were used because they could be shaped easily, gold being especially soft. The discovery that copper could be obtained in sufficient quantities for beating into vessels and weapons was an important step in the use of metals, but the discovery that copper ore would produce copper was probably accidental. Perhaps a block of ore was used in a pottery kiln, and the metal was found after the fire had cooled.

Copper had been smelted and used for two thousand years before the potential of iron became evident. In the course of smelting activities, no doubt iron ores and the substance resulting from smelting them were encountered.

When it was found that hammering the smelted iron ore, while still hot, could produce a workable metal there was still no great use for it because it was no improvement on bronze. Eventually it was discovered that repeated hammering and heating in a fire improved the properties of iron, although it was not realised that the process increased the carbon content. Plunging the hot metal into cold water then produced a hard material superior to any other available.

Heating the metal and then allowing it to cool slowly produced a tougher and less brittle metal, although it was not as hard as the ‘quenched’ iron. Iron is still the most widely used metal today and heat treatment is still an important process for modifying its properties for its many uses.

By approximately 1200 BC all the basic metallurgical arts had been discovered. Of these, the most important are concerned with: (1) the extraction of the pure metal from the ore, (2) the mixing of metals and the addition of impurities to produce different properties, and (3) the heat treatment required to modify the mechanical properties.

2. Find in the text English equivalents to the following words and word combinations:

покращувати, існування, використання, здатність, винахідливість, приводити до, електро- та теплопровідність, з’являтися, відкриття, кування, достатня кількість, вміст вуглецю, зброя, домішки.

3. Make up word combinations from the following words and translate them into Ukrainian:

standard, thermal, everyday, travel, tasks, mechanical, use, natural, conductivity, space, important, nuclear, products, metallurgical, engineering, pure, of living, state, step, ore, arts, properties, iron, skilful.

Дата добавления: 2015-07-25