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tions in one stroke of the press. A progressive die permits successive forming operations with the same die.

In coining, metal is forced to flow into two matching dies, each of which bears an engraved designed.

Wiredrawing dies

In the manufacture of wire, a drawplate is usually employed. This tool is a metal plate containing a number of holes, successively less in diameter and known as wire dies. A piece of metal is pulled through the largest die to make a coarse wire. This wire is then drawn through the smaller hole, and then the next, until the wire is reduced to the desired measurement. Wiredrawing dies are made from extremely hard materials, such as tungsten carbide or diamonds.

Thread-cutting dies

For cutting threads on bolts or on the outside of pipes, a thread-cutting die is used. It is usually made of hardened steel in the form of a round plate with a hole in the center. The hole has a thread. To cut an outside thread, the die is lubricated with oil and simply screwed onto an unthreaded bolt or piece of pipe, the same way a nut is screwed onto a bolt. The corresponding tool for cutting an inside thread, such as that inside a nut, is called a tap.

Assignments:

I.General understanding. Answer the questions:

1.What are dies used for?

2.What is the die operation?

3.What types of dies do you know?

4.What is a wire die?

5.Describe the work of a wire die.

6.What materials are wiredrawing dies made of?

7.What is a thread cutting die made of? Describe the work of a thread cutting die.

II. Find English equivalents in the text:

Гидравлическое и механическое давление; закаленная сталь; твердые материалы; уменьшать до желаемого размера; пробивной штамп; за один ход; штамп смазывается маслом; гайка прикручивается к болту; различные формы штампов; штамп совмещенного действия; алмаз; метчик; применять; использоваться для формирования; инструмент.

III. Match two parts of the sentences according to the text:

IV. Translate the following sentences into English:

1.Для различных операций используют различные штампы.

2.Волочильные доски для проволоки делаются из очень твердых материалов.

3.Резьбонарезные плашки и метчики используются для нарезки резьбы снаружи и внутри.

4.В прессовании штампы используются парами.

5.Резьбонарезная плашка обычно делается из закаленной стали в форме круглого диска с отверстием в центре.

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V. Put the phrases (column B) under the correct headings (column A) to get right parts of a presentation:

VI. According to the texts about machine tools (Units 4, 5), the table (Unit 5, Assignment VI), and the presentation structure (the previous assignment) make a short presentation on one of the machine tools. Don’t forget about clichés (Appendix 2).

VII. 1) Work in groups and design one of these machine tools:

a)a machine tool-helper at home;

b)a multipurpose machine tool.

2)Decide together:

a)the operations the machine tool should be able to perform;

b)the power source it will use;

c)its approximate size and weight.

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Words and word combinations to the part I

Materials Science and Machine Tools

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PART II. METALS

Unit 1

Read the text:

Metals

Metals are materials most widely used in industry because of their properties. The study of the production and properties of metals is known as metallurgy.

The separation between atoms in metals is small, so most metals are dense. The atoms are arranged regularly and can slide over each other. That is why metals are malleable (can be deformed and bent without fracture) and ductile (can be drawn into wire). Metals vary greatly in their properties. For example, lead is soft and can be bent by hand, while iron can only be worked by hammering at red heat.

The regular arrangement of atoms in metals gives them a crystalline structure. Irregular crystals are called grains. The properties of the metals depend on the size, shape, orientation, and composition of these grains. In general, a metal with small grains will be harder and stronger than one with coarse grains.

Heat treatment such as quenching, tempering, or annealing controls the nature of the grains and their size in the metal. Small amounts of other metals (less than 1 per cent) are often added to a pure metal. This is called alloying and it changes the grain structure and properties of metals.

All metals can be formed by drawing, rolling, hammering and extrusion, but some require hot working. Metals are subjected to metal fatigue and to creep (the slow increase in length under stress) causing deformation and failure. Both effects are taken into account by engineers when designing, for example, airplanes, gas-turbines and pressure vessels for hightemperature chemical processes. Metals can be worked using machine-tools such as lathe, milling machine, shaper and grinder.

The ways of working a metal depend on its properties. Many metals can be melted and cast in molds, but special conditions are required for metals that react with air.

Assignments:

I.General understanding. Answer the questions:

1.What are metals and what do we call metallurgy?

2.What are grains?

3.What is crystalline structure?

4.What changes the size of grains in metals?

5.What are the main processes of metal forming?

6.How are metals worked?

7.What is creeping?

II. Translate into English:

Свойства металлов; расстояние между атомами; правильное расположение; сильно отличаются по своим свойствам; кристаллическая структура; размер зерен; форма зерен; закалка; отжиг; волочение; прокатка; ковка; экструзия; структура и свойства зерна; горячая обработка; усталость металла; ползучесть металла; плавка и отливка в формы; способы обработки металлов.

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III. Match terms and their definitions:

IV. Say whether these sentences are true (T) or false (F):

1.A crystalline structure is an irregular arrangement of atoms.

2.The metal work depends on its properties.

3.Large amount of other metals is added to a pure metal.

4.Metals have different properties.

5.When designing airplanes, gas-turbines engineers take such effects as drawing and rolling into account.

6.Coarse grains are less hard and strong than small ones.

V. Ask special questions to the sentences:

1.The separation between atoms in metals is small, so most metals are dense.

2.The properties of the metals depend on the size, shape, orientation, and composition of these grains.

3.Small amounts of other metals are often added to a pure metal and it’s called alloying.

VI. Translate these sentences into English:

1.Металлы — плотные материалы потому, что между атомами в металлах малое расстояние.

2.Металлы имеют кристаллическую структуру благодаря правильному расположению атомов.

3.Чем меньше зерна, тем тверже металл.

4.Закалка и отжиг изменяют структуру зерен и свойства металлов.

5.Легирование изменяет структуру зерен и свойства металлов.

6.Металл деформируется и разрушается из-за усталости и ползучести.

VII. 1) Read the text using a dictionary.

2) With a partner render this text in the form of an interview. Use the questions given below as a plan.

1.Who discovered titanium?

2.Why was titanium of interest only to research chemists for many years?

3.What properties does titanium have? Comment upon them.

4.What fields does titanium use in?

5.What is the evidence of experiment result, having been described in the text?

6.What happens to titanium nickeloid when being at room temperature? When heated to a certain temperature?

A Wonder Metal

The story of titanium is extraordinary. To begin with, it was discovered twice. A British scientist, William Gregor, found it first and called it menachanite, and six years later, in 1797, M.H. Klaproth, a German chemist, also found it and gave it its present name.

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For many years, titanium was of interest only to research chemists — it was considered too brittle to be of any practical value. Yet it was the impurities with which it was usually associated that made it brittle.

It cost the chemists in many countries endless efforts to isolate pure titanium and even more to start producing it commercially. In 1948 the world stock of pure titanium was only ten tons. Today the output is much larger.

Titanium has one surprising property — it is completely inert in biological media, something the medical community was quick to notice. It is being used to make artificial joints and many other things necessary in surgery at the Priorov Central Institute of Traumatology and Orthopedics. Titanium instruments do not corrode, and are thirty per cent lighter than instruments made of stainless steel.

Titanium’s high standard of corrosion resistance, lightness, tensile strength, and the ease of forging, rolling are finding it more and more uses. Titanium alloys are very useful in mechanical engineering, and for chemical and refractory apparatus. Titanium helped Russian design engineers to surmount the sound and heat barriers in supersonic and high-attitude aircraft designing. Moreover, it is still a source of surprise for the investigator.

A group of researches under the leadership of Prof. I. Kornilov produced a material that has a kind of “memory”, as the following experiment shows: a thin bent strip of the new alloy was clamped to a stand, a 500-gram weight hung on the free end. A current was passed through for several seconds, which heated the strip to more than 100 C. As if commanded by an enigmatic force, it straightened out like a tight spring and lifted the load. When the current was switched off, the strip gradually went back to its original shape. The cycle was repeated a number of times, and the strip always “remembered” its original shape. The surprising phenomenon of direct conversion of thermal energy into mechanical is seen with the naked eye.

The explanation is in the crystalline modifications of titanium-nickel alloy which, changing with the temperature, also changes back again.

This is why the material has a “memory” and specific acoustic properties. At room temperature, the alloy called titanium nickeloid becomes soft, ductile and doesn’t produce the characteristic metallic sound when struck. However, when it is heated to a certain temperature, it becomes hard, resilient and ringing.

Titanium and its alloys are coming out in the commercial field — they have already made quite a name for themselves as structural materials.

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Unit 2

Sheet-Metal Forming Area

Read the text:

Metalworking Processes

Metals are important in industry because they can be easily deformed into useful shapes. A lot of metalworking processes have been developed for certain applications. They can be divided into five broad groups: rolling; extrusion; drawing; forging; sheet-metal forming.

During the first four processes metal is subjected to large amounts of strain (deformation). But if deformation goes at a high temperature, the metal will recrystallize — that is, new strain-free grains will grow instead of deformed grains. For this reason metals are usually rolled, extruded, drawn, or forged above their recrystallization temperature. This is called hot working. Under these conditions there is no limit to the compressive plastic strain to which the metal can be subjected.

Other processes are performed below the recrystallization temperature. These are called cold working. Cold working hardens metal and makes the part stronger. However, there is a limit to the strain before a cold part cracks.

Rolling is the most common metalworking process. More than 90 percent of the aluminium, steel and copper produced are rolled at least once in the course of production. The most common rolled product is sheet. Rolling can be done either hot or cold. If the rolling is finished cold, the surface will be smoother and the product stronger.

Extrusion is pushing the billet to flow through the orifice of a die. Products may have either a simple or a complex cross section. Aluminium window frames are the examples of complex extrusions.

Tubes or other hollow parts can also be extruded. In impact extrusion, the workpiece is placed in the bottom of a hole and a loosely fitting ram is pushed against it. The ram forces the metal to flow back around it, with the gap between the ram and the die determining the wall thickness. The example of this process is the manufacturing of aluminium beer cans.

Drawing consists of pulling metal through a die. One type is wire drawing. The diameter reduction that can be achieved in one die is limited, but several dies in series can be used to get the desired reduction.

Sheet-metal forming is widely used when parts of certain shape and size are needed. It includes forging, bending and shearing. The characteristic of sheet metal forming is that the thickness of the sheet changes little in processing. For example, to make the roof of an automobile from a flat sheet, the edges are gripped and the piece pulled in tension over a lower die. Next an upper die is pressed over the top. Finishing the forming operation, in finally the edges are sheared off to give the final dimensions.

Forging is the shaping of piece of metal by pushing with open or closed dies. It is usually done hot in order to reduce the required force and increase the metal’s plasticity.

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