20 Переведите группы слов и предложения. Обратите внимание на употребление предлогов перед герундием: in – при; on, upon – по, после, при; by – путем, посред­ством, при помощи; without – без.

in building, in melting; on heating, on completing, on melting; by introducing; without employing, without machining

1 In building new metallurgical works, engineers have to solve many different problems. 2 In melting steel, foundrymen use electric furnaces, crucible furnaces and converters. 3 Liquids and gases expand on heating. 4 On completing the construction, the cupola was tested in operation. 5 Casting is a process of forming metal objects by melting metal and pouring it into molds. 6 By introducing new foundry methods the engineers improve the quality of castings and the speed of manufacture. 7 High-grade castings cannot be produced without employing electric furnaces. 8 Most castings cannot be employed as parts of complex mechanisms without machining and finishing.

21 Преобразуйте простые предложения в предложение с причастным оборотом, следуя модели.

Model: Plastics are a large group of materials.

This group consists of a combination of

different elements.

Plastics are a large group of materials consisting of a combination

of different elements.

1 Plastics are a group of new materials. These materials replace natural products. 2 Plastics achieve high toughness, lightness and strength. These properties win many significant applications for these materials. 3 A successful design in plastics is a compromise among highest performance, attractive appearance, efficient production and lowest cost. This compromise needs satisfying the mechanical requirement of the part, utilizing the most economical resin and meeting other requirements.

22Соедините следующие предложения, использовав коннекторы that is why – вот почему, however – однако, thus – следовательно, таким образом.

1 Plastics are solid in finished state. Plastics arc liquid at some stage in manufacture, (that is why, however) 2 Plastics are light, strong, corrosion-resistant. They have won many significant applications in industry and transportation, (thus, however) 3 Most people have outgrown the impression that plastics are low-cost substitute materials. There are people who still view plastics as cheap and unreliable, (however, that is why).

23 Прочитайте текст и скажите, о чем он.

Расшифруйте данные, характеризующие различные материалы. Обратите при этом внимание на размерность: 1) вес; 2) точку плавления; 3) содержание метал­ла в земле, в морской воде.

В разделе "Aluminium" сообщается о свойствах чистого алюминия, его сплавов и об улучшении этих свойств в процессе обработки.

а) Назовите эти свойства;

б) скажите, с какими элементами сплавляется алюминий;

в) какие процессы улучшают свойства алюминия и его сплавов.

TEXT 3 C

Non-Ferrous Metals

Although ferrous alloys are specified for more engineering applications than all non-ferrous metals combined, the large family of non-ferrous metals offers a wider variety of characteristics and mechanical properties. For example, the lightest metal is lithium, 0.53 g/cm3 the heaviest, osmium, weighs 22.5 g/cm³ – nearly twice the weight of lead. Mercury melts at around – 38°F, and tungsten, the metal with the highest melting point, liquefies at 6,170°F

Availability, abundance, and the cost of converting the metal into useful forms – all play important parts in selecting a non-ferrous metal. One ton of earth contains about 81,000 g of the most abundant metal of land, aluminium. One ton of sea water, on the other hand, contains more magnesium than any other metal (about 1,272 g). All sources combined, magnesium is the most abundant metal on earth. But because magnesium is difficult to convert to a useful metal, it may cost several times that of the least expensive and most easily produced metal, iron billet.

Although nearly 80% of all elements are called "metals", only about two dozen of these are used as structural engineering materials. Of the balance, however, many are used as coatings, in electronic devices, as nuclear materials, and as minor constituents in other systems.