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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 aluminum, steel and copper produced is 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. The initial piece is a thick-walled tube, and the extruded part is shaped between a die on the outside of the tube and a mandrel held on the inside.

Вариант №5.

I. Перепишите предложения, определите степени сравнения прилагательных или наречий, переведите на русский язык.

1. He is the best student in our group.

2. We discussed the most important problems at the meeting yesterday.

3. August is the most rainy season.

4. Better late than never.

5. He is the younger brother.

II. Перепишите предложения, определите видовременные формы глаголов и укажите их инфинитив, переведите предложения на русский язык.

1. My sister lived in Leningrad last year.

2. It often rains in autumn.

3. Many different crops have grown on our farm.

4. Farmers had harvested crops by the end of the month.

5. Third-year students will work at the computer centre.

III. Перепишите предложения, подчеркните в каждом из них модальный глагол или его эквивалент, переведите предложения на русский язык.

1. You must not smoke here.

2. They could start the experiment yesterday.

3. It may rain today.

4. I have to come in time.

5. He is able to play chess.

IV. Перепишите предложения. Подчеркните причастия, установите функции каждого из них (определение, обстоятельство, часть сказуемого). Переведите предложения на русский язык.

1. The student translating the text is my friend.

2. He is going along the street.

3. The working man is my father.

4. When done this work will give good results.

5. We saw the houses built many years ago.

V. Прочитайте и устно переведите весь текст. Письменно переведите абзацы 2,4.


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