Control work.

Прочтите текст и выполните следующие после текста упражнения:

ARC WELDING

In arc welding the workpieces are not melted by a flame. They are melted by an electric arc. In order to

create the arc, a powerful electric current must be provided. The current must be at least 60 A. otherwise the arc

will not create enough heat. For thicker workpieces, the current may be 250 A. In order to earn this current, the

cables from the transformer should be quite thick or else they will overheat. To supply the necessary current the

transformer is used and to complete the electric circuit an earth clamp is used, which is attached to the

workpiece. Then the current flows around the circuit and the arc appears. It must be securely attached,

otherwise an arc will appear between the clamp and the workpiece. To strike the arc. the transformer should be

switched on first. The electrode holder contains an electrode rod which provides the filler metal to join the

workpieces. As the current flows between the electrode and the workpiece, the tip of the electrode melts and

falls onto the workpiece. The electrode must be moved across the joint continuously, if it is moved too quickly

neither the electrode nor the workpiece will melt.

While choosing an electrode type it is necessary to know:

a. Position to which the workpiece is to be welded.

b. Type and thickness of metal used.

c. Type of welding current.

d. Class of work: deep penetration, surface quality, etc.

I. Найдите в правой колонке перевод английских слов и фраз

(пишем по образцу: 1 – l ) :

1. arc welding а. перегреваться

2. to melt b. держатель

3. flame с. зажим заземления

4. to overheat d. прикреплять надежно

5. electric circuit е. зажигать дугу

6. earth clamp f. электрод

7. to appear g. присадочный металл

8. to attach securely h. плавиться

9. to strike the arc i. глубокое проникновение

10. holder j. электрическая цепь

11. electrode rod k. наплавляться (падать на ...)

12. filler metal 1. дуговая сварка

13. deep penetration m. качество поверхности

14. surface quality n. появляться

15. to fall onto o. пламя

II. Найдите соответствующие ответы на во и напишите их: (например 6-F )

Questions Answers

1.How are the workpieces melted in arc welding? a. For supplying the necessary current.

2. How is the arc created? b. By an electric arc.

3. What is the transformer used for? c. An arc will appear between the clamp and the

workpiece.

4. Why must the electrode be moved across the

joint continuously?

d. By a powerful electric current.

5. What will happen if the earth clamp is not

securely attached?

e. Otherwise neither the electrode nor the workpiece

will melt.

III. Complete the sentences with the proper verb form (conditional sentences)

(Запишите полностью предложения):

1.If people (eat) less, they (feel) better. It’s a rule.

2.I (not go out), if I (be) you. It’s raining.

3.If it (rain), I (not go) to the park. – I agree.

4. If I (have) a lot of money, I (travel) round the world.

5. If the weather (be) nice 2 days ago, I (go) to the beach.

IV. Complete the sentences with Perfect forms (запишите полностью предложения):

1. I (read) already this journal.

2. She already (make) the cake when I came.

3. They (finish) their work by tomorrow evening.

4. Sue not (return) the book to the library yet.

5. My friend (complete) the work before I came.