Unit 2. PHYSICAL PROPERTIES OF METALS AND ALLOYS

ГОУ СПО Уральский государственный колледж им. И.И. Ползунова

Сборник текстов и упражнений

По дисциплине «Английский язык»

для развития лексических навыков в области профессионально-ориентированного общение по специальности

«Металлургия цветных металлов»

Екатеринбург, 2009 г.

Автор: Готочкина Т.В. – преподаватель Уральского государственного колледжа им. И.И.Ползунова

Рецензент: Малина Л.П. – преподаватель Уральского государственного колледжа им И.И. Ползунова

Пояснительная записка

Данное пособие предназначено для работы со студентами, обучающимися по специальности «Металлургия цветных металлов», и ставит своей целью подготовить их к чтению и переводу соответствующей технической литературы на английском языке, а также сформировать базовые навыки и умения для устного общения на языке по данной специальности.

Пособие содержит адаптированные и оригинальные тексты из иностранных журналов и научно-технической литературы, а также тексты, переведенные с русского на английский язык. Тематика текстов следующая: металлургия, литейное производство, специальные способы литья, виды печей, свойства металлов и сплавов. Содержание текстов соответствует программам специальных дисциплин, и по своей сложности данные тексты предназначены для студентов III курса, имеющих базовые знания по дисциплине «Английский язык».

Тексты снабжены упражнениями, рассчитанными на активизацию лексического и грамматического материала. Выбор упражнений и их последовательность обусловлены характером текстов. К текстам даются пояснения, облегчающие понимание и перевод отдельных мест, представляющих определенную языковую трудность.

Пособие может быть использовано для самостоятельной работы студентов.

Unit 1. METALLURGY

SOME WORDS ABOUT METALLURGY

Metallurgy is one of the oldest of arts but one of the youn­gest of sciences. Many of our metals were known in ancient times, but it is only within the last century or two that the knowledge of the properties of the metals has made it possible to apply them in any extended way for industrial pur­poses.

With the development of physics of metals, metallography, theory of heat treatment, and other phases of the science of metals, the field of metallurgy has broadened.

Metallurgy in this broader sense falls into three divisions: chemicalor extractive, physicaland mechanical.Chemical me­tallurgy includes the metallurgical processes involving chemi­cal change and the methods of production and refining.

Physical metallurgy deals with the nature, structure, and physical properties of metals and alloys.

Mechanical metallurgy includes the processes of working and shaping metals — processes which do not involve chemical changes.

NOTES AND COMMENTARY

EXERCISES

I. Find in the text the English equivalents of these Russian word combinations.

1) в промышленных целях

2) применять

3) метод производства

4) очищение от примесей, улучшение качества

5) свойства металлов

6) теория термической обработки

7) в широком смысле

8) химическое изменение

9) включать

10) сплавы

11) обработка

12) извлекать

II. Answer the questions.

1) What phases of the science of metals do you know?

2) What does physical metallurgy deal with?

3) What does mechanical metallurgy include?

Unit 2. PHYSICAL PROPERTIES OF METALS AND ALLOYS

The word constitution used with reference to metallic sub­stances does not have the same meaning as composition. Con­stitution denotes the manner of arrangement of the metal atoms as to geometric form in solid crystals, and the regular or or­dered arrangement of different kinds of metal atoms and their relation to each other in such a crystal.

The pattern formed by this orderly arrangement of the atoms is known as the space lattice.

Most metals crystallize with one of the three following lattice structures:

Close-packed cubic: copper, nickel, lead, aluminium, cobalt, silver, gold, platinum.

Body-centred cubic: iron, molybdenum, tungsten, chromium.

Hexagonal close-packed: zink, cadmium, magnesium, beryllium, titanium.

This union of atoms into a geometric array is the physical difference between liquid and solid metal.

The formation of metal crystals within a melt begins at each cooling surface of the liquid mass and extends from the exterior to the interior as heat is lost from the mass. Every change in the conditions of cooling, such as increasing or decreasing the rate at which heat is conducted away from the freezing mass, will have an influence on the size and shape of the crystals and, therefore, on the constitution and properties of the solidified mass.

Melting and Boiling Points. -The temperature at which a metal melts, is called the melting point, the metals of lower melting points are generally the soft metals and those of high melting the hard metals.

The boiling point of a substance depends on the surrounding-pressure. The term "boiling point" refers to the temperature at which the metal boils under normal atmospheric pressure.

 Electrical Conductivity. -The electrical conductivity of a substance is the electrical conducting power of a unit length per unit of cross-sectional area. The electrical resistance of metals or alloys is increased by decreasing the size of the cry­stals and, therefore, increasing the number of crystal bound­aries. In general, all metals increase in resistivity with increase in impurities. The resistivity of metals is also increased in most cases by an increase in temperature.

Heat Conductivity. - Heat conductivity is measured as the heatconducting ability of a unit length or thickness of a sub­stance per unit of cross-sectional area.

Magnetism. - Magnetism is measured as the magnetic for­ce exerted by a unit volume of a substance under standard ma­gnetizing force. Iron, cobalt and nickel are the only metals possessing considerable magnetism at room temperature, and they become non-magnetic when heated to a certain tempera­ture. Strong permanent magnets have been made chiefly of one of several compositions of steel, but in recent years a number of magnet alloys of much greater magnetism, able to exert forces many times their own weights, have been de­veloped.

Density and Porosity. - Porosity, the quality of containing pores is lack of denseness. Density, on the other hand, denotes weight per unit of volume. The distinction will be manifest from the fact that some heavy metals, like grey cast ironware porous enough to leak under heavy hydraulic pressures, whe­reas some lightweight metals, like aluminium, are dense and compact.

Most metals expand on heating and contract on cooling.

Colour. - Most of the metals are silvery white or grey in colour. Copper is the only red metal, and gold the only yellow one, although a number of copper-base alloys are also yellow. All solid metals have metallic lustre, although the true colour and lustre of many metals are often obscured by a coating of oxide — which may be white, grey, red, brown, bluish, or black.

NOTES AND COMMENTARY

EXERCISES

I. Answer the questions.

1) Name the main physical properties of metals and alloys.

2) What does the boiling point of a substance depend on?

3) When do most metals extend?

4) What is the difference between liquid and solid metal?

5) What metals possess considerable magnetism at room temperature?