Text a Welding

In our country a higher proportion of metal parts is joined by we ding. This process finds widespread application in almost all branches of industry and construction.

Welding is not a new process. This process was first used by the ancients as a means of joining metal has continued through the years to the present day.

An electric arc was discovered by Russian engineer V. V. Petrov. 7 years later it was described by an English physicist Devi. Petrov predicted the use of electric arc was used for metal welding. For the first time elecric arc was used for metal welding with carbon electrode in 1882 by Russian engineer N. N. Bernardos. It is called Bernardos 's process of welding. But the Bernandos system of arc welding was difficult and dangerous. Later Slavianoff repiased the carbon electrode with a metallic electrode.

Welding is a method of causing fusion between two pieces of metal to form one homogeneous mass of metal.

Welding process may be classified according to the source of energy employed for heating the metals and the state of the metal of the place being welded.

In fusion welding the welding area is heated only to a by a concentrated source of heat to a molten state and filler metal plastic or must be added to me weld.

Pressure welding process involves the heating of the metallic parts slightly fused state and forcing them together with external pressure.

In accordance with the method applied for fusing the filler metal to procedures' are classified as manual, semi- automatic or automatic welding.

The three main welding process are: 1, Arc welding. 2. Resistance welding. 3. Gas welding.

Arc welding is a non- pressure (fusion) welding process where in the welding heat is obtained from an arc either between the base metal or weld metal and an electrode or between two electrodes. In arc welding electric current passes through an electrode and the work thus forming an arc. When the arc is established a high temperature exists between the arc

terminals, heating the tip end of the electrode wire and a small area on the surface of the parent metal to a liquid state. Metal arc welding is probably the most widely used of all present day welding processes.

The main advantages of the arc welding is the absence of arc blow and it is easy to control and to maintain. Arc welding is usually faster because of larger electrodes.

Exercise 9. Read the text and find

a) the definition of welding;

¹ procedure - метод; процесс производства.

2. the definition of arc welding;

3. the advantages arc welding.

Exercise 10. Complete the following sentences:

1. Welding lis ...

2. This process finds ...

3. An electric arc was discovered

4. The threу main welding process arc ...

5. Arc welding is

Exercise 11. Define which of this statements correspond to the text.

Use the expressions: that's right, 1 don't think so, 1 can't agree, that's wrong.

1. The earliest means of welding is arc welding.

1. Welding is a method of causing fusion between two pieces of metal to form one homogeneous mass of metal.

2. Arc welding is a pressure welding process.

3. Forge welding is the most Widely used of all present day welding process.

Exercise 12. Answer the following Questions:

1. Is welding a new process?

2. What process is called welding ?

3. What we ding process was the earliest one ?

4. By whom was an electric arc discovered ?

5. Who used the electric arc. for metal welding with carbon electrode for the first time?

6. By whom was a new method of welding with metal electrode suggested

7. What are the four main process of fusion of two masses of metal?

8. What kinds of process is arc welding?

9. What arc the main advantages of arc welding?

10. Is are welding widely used in present day welding process?

Exercise 13. Get ready to retell the text

Resistance welding is a pressure process and the oldest of modern fusion welding processes. It was discovered by the English physicist James Joule in 1856.

The fundumental principle upon which all resistance welding is based is that when an electric current is sent through metal the resistance of the metal to this electric flow heats the metal.

By applying sufficient current, the resulting high temperature may produce fusion temperature and make welding possible.

Resistance welding has a number of advantages. It is fast, there is very little warpage of the metal, the process can be accurately controlled, and the welds are consistently uniform. This type of welding is particularly well suited to all forms of automatic production.

Gas welding is a fusion - welding process in which the required heat is supported by a high - temperature flame obtained by a mixture of two gases. The two gases are mixed in proper proportions in a welding blowpipe or torch which is designed so that the operator has complete control of the welding flame.

Joining of base metals is achieved by fusion of a metal deposited between the surfaces of the metals to be joined.

The oxygen - acetylene mixture is almost universally used in we ding industry. The highest temperature oxyacetilene is about 6.000°F.

Exercise 14. Read the text В and give it a suitable title. Give your reasons for the choice.

Exercise.15. Read the text and find.

a).the definition of resistance welding.

b).the definition of gas welding.

c).the advantages of resistance and gas welding.

Exercise 16. Define which of these statements is right or wrong using the phrase

a). it is right b).it is wrong

1. Resistance welding has is a non - pressure welding process.

2. Resistance welding has no advantages.

3. Gas welding is a fusion - welding process. 5. The two gases are mixed in a torch.

Exercise 17. Complete the following sentences:

1. Types of resistance welding are

2. In gas welding required heat is supplied by

3. The oxygen - acetylene mixture is

Exercise 18. Answer the following questions:

1. In what welding processes is pressure applied?

2. Who discovered the principle of resistance welding?

3. is the resistance welding the oldest of modern fusion welding processes?

4. What are the types of resistance welding?

5. What kind of process is gas welding?

6. What gas mixture is most commonly used in welding industry?

7. What is the highest temperature of the oxyacetylene flame?

Exercise 19. Look through text В again and express the main points of in three sentences.

TEXT С

Spot Welding.- This process consists of holding two or more metals between suitable electrodes which pass a heavy current through the material to be welded.

The electrodes then arc forced together by pressure of sufficient force to join the. surfaces of the base metals in a spot.

Spot welding is applicable to many kinds of work. The welds are rapidly made. • Ferrous and non- ferrous metals and their alloys may be spot welded. This process is suitable for welding parts of automobiles, airplanes, refrigerators.

Butt - Welding. - By this process the parts to be welded arc gripped¹ mechanically and pressed together while heat is generated by passage of a heavy current through the area of the joint.

Butt welding is used extensively for resistance welding work. Pipes, tubing, bare, rods may be butt welded.

Flash Welding is another type of butt welding, the difference consisting in the method of hearing the base metals.

Seam Welding is a resistance welding process which consists of passing two or more base metals between electrodes which are in the form of rollers². The current is transmitted through the electrodes to the metals. The mechanical pressure required for forcing them together as well as the current is transmitted by the roller- shaped electrodes. Refrigerators, metal соnitainers, automobile mufflers are produced by seam welding.

Projection Welding is similar to spot welding land consists of joining two pieces of metal, one or both of which have mechanically formed projections. The purpose of the projection is to localize the current.

Exercise 20. Read the text and give it a sutable title. Live your reasons for the choice.

Exercise 21. Translate this text in writing.

Exercise 22. Write out all special terms from the text and give their Russian equivalents.

Exercise 23. Name the main types of Resistance welding.

Exercise 24. Summarizing the information of texts A and В and С write an abstract using the key- patterns (see p. ).