1) Metals have served man to create new machines.
2) The first definition of metals was given by M.V. Lomonosov.
3) Metals have found wide application because of their properties.
4) There are some classifications of metals based on their properties and composition.
5) An alloy is a simple metal combined with some other elements.
6) Some metals are called refractory metals.
7) Metals are found in the form of ores.
8) There are many methods used to separate metals from ore.
9) Impurities are separated and removed as slag.
10) About two thirds of all elements found in the earth are metals.
11) Cast iron is produced in cupolas.
12) Ore is a metal combined with some impurities.
13) Metals used in industry are called engineering metals.
Read the additional text about metals and retell it in Russian.
There are many superstitions () about iron. The Romans () believed, if you drew (, ) three circles in the air around anyone and three on the ground with a bit () of iron, that person would be bewitched (). It is interesting to note that wedding rings ( ) in Ancient Rome were made of iron.
We find a lot of superstitions among the Creeks and the Egyptians. But we do not have to go back to Roman days for curious superstitions and beliefs (). We can find them nowadays (today). There is still a superstition among some people to-day about horseshoes (). They believe that horseshoes bring good luck or bad luck. Though people were superstitions about iron it turned out () to be a much better metal for making tools than bronze. And so the Bronze Age gave ways to the Age of Iron.
SUPPLEMENTARY TEXTS FOR READING
Read and translate the following texts using a dictionary. Write down unknown words with their translation. Learn them.
HARDENING AND TEMPERING
Hardening means making harder. Steel which contains more than 0.75 per cent carbon becomes very hard and very brittle when hardened. High carbon steel is hardened by carrying out the following operations. The steel is first slowly heated to a proper temperature. Having been heated to red color, it is then rapidly cooled in oil, water, brine or some other liquid. The process of cooling is called quenching the steel, thus the hardening operation consists of heating and quenching. Alloy steels are usually hardened by special ways. The hardness produced by heat treatment depends upon the: 1) amount of carbon in steel; 2) temperature of heated steel; 3) speed of cooling.
The critical temperature, or critical point, is the temperature at which a piece of steel is properly hardened. When steel is heated to the critical temperature, the grain becomes very fine, that is the crystals get smaller, some other changes in the physical properties of steel take place, too, in this condition. The critical temperature is different for different kinds of steel. It depends upon the amount of carbon in steel. The more carbon the steel contains, the less it should be heated for hardening. In other words, the more carbon the steel contains, the lower is the critical point. The critical temperature may be tested with a magnet. Steel is magnetic until it reaches the critical temperature, then it is non-magnetic. Thus, a piece of steel to be hardened may be heated until it becomes non-magnetic; it should be then rapidly cooled (quenched).
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Temper is the hardness, toughness and brittleness of a metal. Tempering, also called drawing the temper, means taking some of the hardness and brittleness out of hardened steel so that it could do good work. Having been tempered, the steel becomes stronger because its grain gets finer; as we already know, steel with a coarse grain is weaker than steel with a fine grain. Hardened steel is too hard and too brittle for many tools. A hardened cutting tool will break easily while cutting with it; it is therefore better to have a cutting tool tough and not too hard. Tempering brings about this condition.
Having hardened the steel, it is polished and heated. The different temperatures will show in the form of different colors on the polished surface. Each temperature or color is a different hardness or temper. The temperatures for tempering are from 400 to 600 degrees of Fahrenheit. When the right color appears, the steel is cooled (the speed of cooling is not important here). Thus the steel is a little softened and will be tougher and less brittle.
STRUCTURE OF METALS
Strength together with plasticity is the combination of properties that makes metals so valuable in industry. In addition to strength and plasticity, metals have many favourable characteristics, such as resistance to corrosion, electrical and heat conductivity, etc.
The characteristics of metals are due to two structural factors: first, the atoms of which the metallic state is composed; and second, the way in which these atoms are arranged.
When a metal becomes solid, it crystallizes. The crystallization or solidification is accompanied by a complete change in the atomic arrangement of the metal. The atoms of liquid metal become arranged into a definite pattern, forming small solid bodies of regular geometric shape such as cubes, etc., when crystallization occurs.
If liquid is cooled slowly in a crucible, nuclei form at the temperature of freezing, and these nuclei continue to grow until the liquid has changed to solid.
Knowing that metals are composed of many crystals or grains, and that each grain in turn is composed of a great many atoms all arranged in some pattern, how can we understand the plastic flow that must take place when metals are deformed during a bending operation or during the drawing out of a piece of a metal? This deformation may be understood as shearing; that is, when a metal is subjected to stresses exceeding its elastic limit, the crystals of the metal elongate by an action of slipping or shearing which takes place within the crystals and between the crystals. If deformation of the metal continuous, the crystals become remarkably elongated. This plastic flow of the metal, resulting in permanent deformation of the crystals is accompanied by marked changes in the physical properties of the metal. The tensile strength, yield point and particularly hardness are increased, but not the scratch hardness or ductility of cutting, as in machine operations in a lathe. The stiffness remains about the same, though in some cases it may be increased as much as 3 per cent. With the increase in hardness and strength, the plasticity or formability is reduced. Ultimately, if deformation of the crystals is continued, the metal becomes brittle. This process changing the physical properties of a metal is called work-hardening.
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If the temperature of work-hardened metal is raised above normal, the deformation begins to disappear and the metal returns to the normal condition of structure and properties.
NONFERROUS FORGINGS
Nonferrous forgings are metal shapes produced by hot-working nonferrous metals, subjecting them to hammering and pressing operations. The result is the compression, bending, twisting or extrusion of the metal so that various parts of the forging are formed by pressure against dies.
Die-pressed or hammered forgings offer an efficient and economical method of producing irregularly-shaped metal parts from slugs cut from ingots and rods. The result is a strong, dense metal part, closely resembling the shape and size of the finished product, thus insuring a minimum of scrap metal in the final procession operation. Such forgings are freed of excess material and are ready for machining or further finishing operations.
Grain structure is uniform and dense, eliminating the disadvantages of porosity and rough surface finish. Nonferrous forgings also have high tensile strengths; the great strength and nonporosity often permit reduction in weight of parts previously produced by other processes. Fewer finishing operations are necessary, and the required machining may be performed with maximum speed. However, greater strength naturally reduces machinability.
Many nonferrous alloys are readily adaptable to the forging process and have been successfully used. Among them are forging brass, nickel, silver, leaded brasses, aluminum bronze, manganese bronze, silicon bronze and several aluminum alloys.
At present, nonferrous forgings are used for many purposes: for electrical and chemical equipment, in welding and in many other cases. Brass forgings have an important part in air compressors, compressed gas valves, gas and water meters, oil burner equipment, etc.
Nonferrous forgings can be provided in a great variety of finishes such as bright polished, plated with nickel, chromium, copper or other metals.
COLD WORKING OF STEEL
Part I
Steel is hot worked when it is in a homogeneous or heterogeneous austenitic condition. Hot working is the working of metals above the annealing temperature, so that the deformed metal becomes annealed before cooling to room temperature, and therefore has a normal grain structure with normal ductility and toughness. Cold working passes under quite different conditions; it is generally accompanied by many annealings of the metal being cold-worked.
Cold rolling, for example, like hot rolling may be carried out on a two-high or four-high rolling mill, or in a continuous rolling mill. Cold rolling is continued until the rolled section becomes too hard to continue the process, or until it reaches its final size. It may become necessary to anneal the metal after several passes through the cold rolling mill, in order to keep it in a workable condition. If annealing is carried out in an open furnace, pickling again is necessary before re-rolling to remove the scale and clean the metal. Today annealing of cold-rolled products is usually carried out in special furnaces that complete the annealing without the formation of scale.
Cold drawing is carried out by drawing the metal through a succession of conical tapering holes in a die plate. Die materials are: steel, cast iron, tungsten carbide and diamond. Shapes varying in size from the finest wire to those having a cross-sectional area of several square inches are commonly drawn. Due to the difficulty of making dies and small need for any other form, the fine sizes are drawn only to a round cross-section; larger sizes may be drawn to square, round, or irregular cross-sections, the larger sections being drawn on a drawbench. Metals can be formed to much closer dimensions by drawing than by rolling, and for this reason large quantities of steel and brass are cold drawn.
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Multiple die machines are often used to produce wire. In these machines the wire passes through one die, around a capstan, through a second die and round another capstan, etc. As many as twelve dies may be used in a machine. Having gone through each die, the wire of course, is greatly elongated. The speed of drawing in multiple die machines may reach 10 000 feet per minute on fine wire. The die, or drag plate as it is often called, may be made of a number of materials, tungsten carbide having largely replaced other die materials because of its great ability to retain its shape during the drawing operation.
Part II
In drawing seamless tubing the metal is forced between the die and the mandrel, and in this way the wall thickness, the outside diameter, and the inside diameter may be controlled. As in any cold-working operation, the metal should be free from scale and other defects before it is cold-drawn.
Cold-working operations may be divided into two large classes:
1. Where the cold working is carried out for the purpose of shaping the articles only; and where the hardening effect is not desired and must be removed at various stages of plastic shaping as well as from the finished article by annealing.
2. Where the object of cold working is not only to obtain the required shape but to harden and strengthen the metal, and where the final annealing operation is not carried out.
In order to shape metals by cold working they must be annealed at proper intervals. Otherwise deformation must be carried out at temperatures where annealing is simultaneous with hardening, as in the hot working of metals. The selected method will depend on the individual metal as well as on the desired product. Metals vary greatly in the ease with which they deform. Copper, for example, may be worked readily at room temperatures, whereas some steels can only be worked at a red heat. Practically all metals and alloys become brittle very near their melting points and hence must not be worked at too high temperatures. There are metals that can be worked only in certain temperature ranges without cracking. Thus zinc must be worked at 200 to 300 degrees of Fahrenheit; nearly pure iron must not be worked in the blue heat range. Brass must not be heated too near its melting point in annealing, also, or it becomes burnt.
TOPIC: GEOGRAPHICAL POSITION OF GREAT BRITAIN
Part I
The United Kingdom of Great Britain and Northern Ireland is situated on 2 large islands and 5000 smaller ones. These are the British Isles. Great Britain, the largest island in Europe, includes England, Scotland and Wales. It is separated from Ireland by the Irish Sea, from the European Continent-by the North Sea, the English Channel and the Strait of Dover. On the west coasts Great Britain is bound by the Atlantic Ocean.
The southern part of Ireland is an independent republic.
The greater part of the surface of England and Ireland is flat. The northern part of Scotland and Wales is mountainous and rocky. The highest mountain of the country is Ben Navis in Scotland. The main rivers are short but can be used by ships. There is a number of lakes in the country. The coastline of the country has excellent harbours.
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As a rule, the climate depends on the geographical position of the country. The British Isles are washed by the warm current of the Gulf Stream. So the weather is mild, wet, cloudy, windy and changeable.
The total area of the country is about 21600 square miles or 245000 square kilometers. The population of Great Britain is about 55 million, 44 being Englishmen. Nearly all people speak English, but some speak Celtic languages.
The main cities are London, Birmingham, Liverpool, Manchester.
to separate ();
to include ;
to wash ;
to depend on ;
to be situated ;
to be bound ;
island ;
coast , ;
surface ;
harbour ;
current ;
independent ;
flat , ;
mountainous ;
rocky ;
changeable ;
moderate ;
mild ;
wet ;
cloudy ;
total , ;
as a rule ;
the English Channel ;
the Strait of Dover --;
Ben Navis ;
The Gulf Stream ;
Celtic .
TOPIC: POLITICAL SYSTEM AND PARTIES OF GREAT BRITAIN
PART II
Great Britain is a parliamentary monarchy. The King or the Queen is at the head of the state but does not play an important part in the political life of the country. The Queens powers are limited by the Parliament. It consists of 2 chambers: the House of Lords and the House of Commons. The House of Lords has 850 inherited members and the House of Commons has 660 elected members. The Government is formed by the Prime Minister, usually the leader of the party that has the majority in the House of Commons. The highest executive power is the Cabinet. It consists of 18 ministers and the Prime Minister. The country is ruled by the Government in the name of the Queen.
At present there are 4 main political parties in the country. The Conservative Party and the Liberal Party were founded in the middle of the 19th century and were supported by the rich people. The Labour Party was founded by the Trade Union Congress at the beginning of the 20th century. The Communist Party is the only party that defends the interests of the working people. It was founded in 1920.
to be limited ;
to rule , ;
to defend ;
to support ;
to be founded ;
monarchy ;
at the head ;
power(s) ;
chamber ;
in the name of ;
majority ;
parliamentary ;
executive ;
elective ;
inherited , ;
the House of Lords ;
the House of Commons ;
the Conservative Party ;
the Liberal Party ;
the Labour Party ;
the Trade Union Congress -;
the Cabinet ;
the Prime Minister -.
TOPIC: INDUSTRY AND AGRICULTURE OF GREAT BRITAIN
PART III
Great Britain is highly developed industrial capitalist country. It is a member of the Common Market. Before the Second World War the country was an old naval powerful state. After the war Great Britain has lost almost all its colonies, some of them fell under the influence of the USA, others obtained independence.
During the last decades there has been a great change in the structure of British industry. The main British exports were coal and textiles. But now British export of machinery, vehicles and electrical goods has greatly increased.
There is no variety of mineral resources in the country, but coal deposits take the 6th place in the world. Coal-mining is one of the oldest industries together with ship-building and cotton industries.
Sheffield is the centre of steel industry. Manchester is a textile centre. Liverpool is an important port as well as London. Clydeside and Belfast are famous for their ship-building.
One-third of the budget has been devoted to arms expenditure. Military industry receives more state funds.
Four-fifth (4/5) of the land is devoted to agriculture. It provides employment for more than 1 million people. The main branch of British agriculture is dairy-farming. The main grain crops are wheat and barley.
to obtain ;
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the Common Market ;
to fall under the influence ;
to increase ;
to develop ;
to be famous for -;
to receive ;
to provide ;
production ;
variety ;
deposit ;
vehicle ;
dairy-farming ;
grain crops ;
barley ;
wheat ;
arms expenditure ;
resources ;
to manufacture ;
employment ;
to devote , ;
naval ;
coal-mining
Bibliography
1. .., .. . .- /: , 2004. 352 .
2. .. . .: , 1991. 225 .
3. .. . .: . ., 1990. 416 .
4. .., .. .- .: . ., 1991. 320 .
Contents
| Lesson I: Metals and Men Lesson II: Metals and non- metals Lesson III: Classification of metals Lesson IV: Production of Metals Lesson V: Metals as engineering materials Supplementary texts for reading Topic: Geographical Position of Great Britain (Part I) Topic: Political System and Parties of Great Britain (Part II) Topic: Industry and Agriculture of Great Britain (Part III) Bibliography |
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