2017-10-25
1330
Steel Plates
The Importance of Iron and Advent of Steel
Life seems impossible now without iron, the cheapest and most important metal we use. Iron is extracted from a rocky material called iron ore. Like many elements, iron is too reactive to exist on its own in the ground. Instead, it combines with other elements, especially oxygen, in ores. The chemical process for extracting a metal from its ore is called smelting.
The first people who discovered how to extract iron from iron ore were the Hittites, a powerful group of people living in Asia Minor and Syria - south of the Black Sea. They kept the process a closely guarded secret. The Egyptians, for example, had to pay the Hittites in gold four times the weight of iron and once deceived them with lumps of bronze covered with a thin layer of gold.
The smelting of iron was the most important metallurgical development. Iron-ore is plentiful all over the world, therefore it may seem surprising that such a long time elapsed before iron was produced. The reason was that the furnaces used to smelt copper were not hot
Sometimes the early iron-workers, or smiths, accidentally produced a steel article instead of an iron one. Steel is iron with a small percentage of carbon in it. The carbon came from the fuel in the furnace in which the iron was heated. The smiths later learned from experience how to introduce this carbon when they wanted to produce steel.
Steel is stronger than iron, and can be made stronger still by quenching, which is the sudden cooling, in water or other fluids, from red-heat. However, steel becomes very brittle when made extremely hard, and as each smith used his own method the quality of the steel varied a great deal. Often a sword made by a poor smith snapped just when it was most needed.
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Вариант 4
1. Поставьте предложения в страдательный залог (Образец: Mother waters the flowers in the evening. — The flowers are watered in the evening (by mother). Переведите исходное предложение и предложение в страдательном залоге.
1. I spent all my money on books last month. 2. We shall do all this work today: there is too much of it. 3. When I start doing this, somebody always stops me. 4. Don't leave these sweets on the table: somebody will eat them. 5. The bees attacked the bear when it tried to take their honey.
2. Раскройте скобки, употребляя глаголы в Active или Passive Voice. Переведите предложения.
1. They (wrote/were written) many articles for the magazine last year. 2. All the graduates (defend/ are defended) their candidate theses before the Examination Board. 3. Many compulsory subjects (will be taken/will take) by the first-year students. 4. These data (are refered to/ refer to) often. 5.The water (has boiled/has been boiled) already.
3. Раскройте скобки, употребляя глаголы в Passive Voice. Переведите предложения.
1. Progress (to make) every day in the world of science. 2. This problem (to give) much attention to at present. 3. The new cosmic achievements (to speak) about. 3. The delegation of foreign students (to show) all the laboratories of our institute last week. 4. Many subjects (to study) in the first year. 5. I (to surprise) by his present for my last birthday.
