Контрольная работа по дисциплине «Английский язык»
Скачать 0.7 Mb.
|
Metals in the Service of Man Let us consider why metals play such a great role in man’s activities. Wood and stone are both older in use, yet to a considerable extent they have been replaced by metals. In spite of the great progress of chemistry and increasing output of plastic materials metals are still used for most of machines, structures and instruments. If there were no metals, no railway, airplane, car, electric motor, turbine or pipeline could operate. The reason for the increased use of metals is to be found in their characteristic properties. The most important of these properties is their strength or ability to support weight without bending or breaking. Resistance to atmospheric destruction, plasticity and the ability to be formed into desired shapes are remarkable as well. Some metals have also special properties – two of which are the ability to conduct electric current and the ability to be magnetized. Nowadays we know that over three quarters of existing elements are metals. We know approximately over 80 metals and several thousand alloys. Most metals are usually found in nature as minerals or ores, where they exist in chemical combinations with other substances. Metallic ores contain metals combined with oxygen, sulphur or other metals. Ores are usually mined and passed to the metallurgist for refining and purification. The ores are treated by fire or chemically by the process called smelting. Ores have to pass through this very complicated process before pure metals are obtained. But pure metals are comparatively seldom used because they are rather expensive and their strength is generally insufficient for the purposes of to-day. The most important way in which the strength of metals can be increased is alloying. Alloys are the most important engineering materials. Alloys are obtained by adding various metals or non-metals to the main metallic element.
Variant 7
specialist – automobile – production – phase – accurate – comfortable – ecological – method – optimal – mechanism –
relationship, scientist, structure, researcher, mathematical, systematic, observation, brighten, legislative, experimentally, realize, numerous, closely, influence, powerful, generally, industrial, development, suddenly, illustrate, different, television, valuable, beautify, scientific , producer, resistant, slowly, dictation, weightless, computer, temperature.
5. Переведите предложения, обращая внимание на глаголы с послелогами.
6. Переведите сочетания слов, обращая внимание на перевод существительных в функции определения
Ferrous and Non-ferrous Alloys Both ferrous and non-ferrous alloys are largely used in all branches of machine-building. The principle ferrous materials used are: pig iron, cast iron, wrought iron and steel. Everybody knows various kinds of steels to be applied in industry – mild steels, carbon steels and alloy steels. Pig iron may be said to be the starting point in the production of all other ferrous materials. Metallurgists consider it to contain from 92 to 97 per cent iron. The remainder is carbon, silicon, manganese, sulphur and phosphorus. Cast iron is pig iron which has been modified in structure by remelting usually with the addition of steel scrap and by casting it into moulds. Wrought iron which is now seldom produced is the iron from which nearly all carbon and most of sulphur, phosphorus, etc., have been removed by a process known as puddling. Steel may be roughly defined as an alloy of iron and carbon. The percentage of carbon may bе varied from almost zero in mild steels, up to 2.14 in some tool steels. Besides, alloying elements such as nickel, chromium, molybdenum, silicon, vanadium, tungsten, cobalt and copper are known to be present in these steels. As is known, if metallurgists want to change the properties of the steel they vary either the composition of it by alloying or use heat treatment, or both. Non-ferrous alloys are alloys which have been developed on the basis of non-ferrous metals. They are defined according to their dominant element. Copper-base alloys are used where high thermal or electrical conductivity is the chief requirement. Aluminium-base alloys are used where light weight is a primary requirement. It should be noted that they are widely used due to their high corrosion resistance. Besides, aluminium base alloys have desirable combination of mechanical properties with thermal and electrical conductivity. Magnesium-base alloys are used where light weight is needed. Both ferrous and non-ferrous metals are known to possess in some degree the following properties: elasticity, ductility, malleability, toughness, brittleness, hardness, wear resistance, and corrosion resistance.
. Variant 8
constant – resin – mineral – constitutional – diesel – manual – refrigerator – industrial – communication – to accelerate –
Performance, production, audience, addition, culture, ancient, frequently, deepen, interchangeably, serious, artist, performer, indicate, nearly, creator, musical, successful, probably, language, important, enjoyable, utilize, happiness, absolutely, pleasure, famous, beautiful, personal, electric, effective.
Metals and Alloys From the earliest times metals and their alloys were and are referred to as the basic engineering materials. Lately new branches of industry have been developed, for example, electronic, atomic and space industries. The need for new metallic materials has enormously increased. Metals which were practically unheard of before, such as germanium, plutonium and thorium have come to light. Besides, high-temperature alloys for power plants capable of withstanding oxidation and erosion, new ferro-magnetic materials, constructional steels intended for operating under severe stresses and at extremely high or low temperatures have been developed. Each metal or alloy possesses a certain distinct combination of properties which differs it from other metals and alloys and by which metals and alloys are determined for a given engineering application. This combination of properties may be varied by alloying with other elements. Before starting to study the properties of metals and alloys we should get an idea of what the terms “pure metal” and “alloys” mean. The term “alloy” is commonly used to describe a metallic solid containing two or more metals and metalloids. The properties of an alloy are influenced by the properties of the elements it consists of. As a rule, alloys are defined by their dominant element which is present in a quantity over 50% (per cent) by weight, the remainder are alloying elements and impurities. There are a lot of alloys, for example, copper-base alloys, aluminium-base alloys and so on. The term “pure metal” is used for materials from which almost all chemical elements but one are eliminated. The designation “metal” is sometimes applied in metallurgy to any metallic materials without making any distinction between a pure metal and an alloy. The first definition of the word “metal” was formulated by M.V. Lomonosov in the following way: “A metal is a bright solid that can be forged”. This definition is still true. The metallic luster and the ability for plastic deformation are, in fact, looked upon as the characteristic features of metals. The most important feature of metals, however, is their high electrical conductivity which decreases as the temperature is raised. In conclusion it’s necessary to mention that metals and alloys are the most important engineering materials due to their excellent properties.
|
Похожие:
 | Гаоу впо московский государственный институт индустрии туризма им. Ю. А. Сенкевича | | Методические указания предназначены для студентов 3 курса заочной формы обучения специальности 15. 02. 08 «Судостроение» |
 | Методические указания предназначены для студентов 3 курса заочной формы обучения специальности 26. 02. 06 «Эксплуатация судового... | | Методические указания предназначены для студентов 3 курса заочной формы обучения специальности 26. 02. 06 «Эксплуатация судового... |
| Контрольная работа по дисциплине «Русский язык и культура речи» за 1 п/г – III к | | Материалы промежуточной аттестации для студентов заочной формы обучения для направления подготовки 25. 05. 05. специализации 25.... |
| Деловой английский язык составлено в соответствии с рабочей программой по дисциплине «Иностранный язык» (раздел «Деловой английский... | | Пример: две последние цифры зачетной книжки 18, тогда номер варианта 18; если 28, то |
| Примерные программы среднего (полного) общего образования. Английский язык Авторская программа Ж. А. Суворова, Р. П. Мильруд «Английский... | | Современный русский язык – это язык ХIХ – ХХI вв. Литературный язык – это язык в своей нормированной, образцовой разновидности |