Read and translate the texts and match the titles to the texts

· Shielded Metal Arc welding

· Submerged Arc welding

· Gas-Metal Arc welding

· Non-consumable Electrode Arc welding

1. As a non-consumable electrodes tungsten or carbon electrodes can be used. In gas-tungsten arc welding a tungsten electrode is used in place of the metal electrode used in shielded metal-arc welding. A chemically inert gas, such as argon, helium, or carbon dioxide is used to shield the metal from oxidation. The heat from the arc formed between the electrode and the metal melts the edges of the metal. Metal for the weld may be added by placing a bare wire in the arc or the point of the weld. This process can be used with nearly all metals and produces a high-quality weld. However, the rate of welding is considerably slower than in other processes.

2. In shielded metal-arc welding, a metallic electrode, which conducts electricity, is coated with flux and connected to a source of electric current. The metal to be welded is connected to the other end of the same source of current. An electric arc is formed by touching the tip of the electrode to the metal and then drawing it away. The intense heat of the arc melts both parts to be welded and the point of the metal electrode, which supplies filler metal for the weld. This process is used mainly for welding steels.

3. In gas-metal welding, a bare electrode is shielded from the air by surrounding it with argon or carbon dioxide gas and sometimes by coating the electrode with flux. The electrode is fed into the electric arc, and melts off in droplets that enter the liquid metal of the weld seam. Most metals can be joined by this process.

4. Submerged-arc welding is similar to gas-metal arc welding, but in this process no gas is used to shield the weld. Instead of that, the arc and tip of the wire are submerged beneath a layer of granular, fusible material that covers the weld seam. This process is also called electro slag welding. It is very efficient but can be used only with steels.

Vocabulary

tungsten electrodes вольфрамовые электродыdroplet капля carbon dioxide углекислый газlaver слой weld seam сварной шовsemi-automatic полуавтоматический to submerge погружатьliquid metal жидкий метал

2. Answer the questions.

1. What is the difference between the arc welding and non-consumable electrode arc welding?

2. What are the disadvantages of the non-consumable electrode arc welding?

3. How is electrode protected from the air in gas-metal arc welding?

4. What is submerged arc welding?

Find in the text.

1. вольфрамовый электрод

2. инертный газ

3. окисление

4. высококачественный сварочный шов

5. скорость сварки

6. аргон, гелий, углекислый газ

7. жидкий металл

8. слой плавкого материала в виде гранул

9. листовой металл

10. полуавтоматические сварочные станки

Translate into Russian.

1. In resistance welding, heat is obtained from the resistance of metal to the flow of an electric current.

2. The heat from the arc melts the edges of the metal.

3. A bare electrode is shielded from the air by surrounding it with argon or carbon dioxide gas.

4. Submerged-arc welding is similar to gas-metal arc welding.

5. Electrodes are clamped on each side of the parts to be welded.

6. Resistance causes heat, which melts the metals and creates.

Read the grammar table and use it by the translation of the following text.

Metals and man.
For many centuries metals have served man helping him to conquer nature, to create useful machines and mechanisms.
The world of metals is rich and interesting. Among metals are the old friends of a man: iron (Fe), cooper (Cu), lead (Pb), mercury (Hg), gold (Au), silver (Ag), tin (Sn). At present out of 104 elements of the Mendeleyev Periodic Table about 80 are metals. Metals have found wide application because they possess properties which made them so useful: for example, they combine high strength and plasticity. Some other materials, stone for example, possess strength, but are brittle. Rubber is highly plastic, but it is not strong.
Ancient Romans knew only 8 metals: gold, silver, copper, tin, lead, mercury, antimony, iron.
In 1763 the great scientist Lomonosov knew only 6 metals: gold, silver, copper, tin, lead, iron. He excluded antimony and mercury from the list of metals because of their bad so ductility (forgeability) as ductility to be the main characteristic of metals.
In 1869 Mendeleyev discovered this Periodic System, 50 metals being know by that time.
The first scientific definition of metal was given by M.V. Lomonosov in his book “The first foundation of metallurgy and mining” (Первые основания металлургии и рудных дел) in 1763. He wrote: “Metals are light colour bodies which can be forged” (Металлы – светлые тела которые ковать можно). This definition does not lose its scientific significance even now. It comprises the two main characteristics of metal: plasticity and metallic luster.
Besides, metals possess high electrical conductivity and heat conductivity.
In engineering metals are defined as substances possessing the following properties: metallic luster, plasticity (ductility), high electric conductivity which rises with the decrease temperature.

Text 6

Read and translate the text.

1. Metal arc welding is a method of joining metals by heating, melting and fusing the edges or surfaces together, no mechanical pressure being applied. Metal-arc welding is a fusion welding process.
2. In metal-arc welding, the intense heat, required to melt and fuse metal of the work to be welded, is created by an electric arc. The arc is most widely used source of electrical energy, and, therefore, heat energy for fusion welding. By means of the arc the great amount of electrical energy is transformed into heat energy in a small space (zone).
3. The electric arc is a highly desirable source of welding heat for a number of reasons. It has a very high temperature – 6.000 – 10.0000FF. (according to Fahrenheit) and is able to melt refractory metals and alloys having a very high melting point. The electric arc is the highest concentration of electrical energy used in any industrial process. This property permits (allows) it to produce a large amount of heat in the welding zone.
4. There are two simple ways of using the electric arc to provide welding heat. It can be established (created) between two electrodes or it can be created between the electrode and base metal to be welded. Of course, there are other ways of creating the arc.
5. The stability and other properties of the welding arc depend upon such factors as the current and polarity, the temperature and length of the arc, the type of electrode to be used and its flux coating, the metal to be welded and the type of the joint. Welding equipment is also of great importance.

Vocabulary

welding equipment сварочное оборудование

heating нагревание

melting плавление

fusing плавка

electrical energy электроэнергия

properties of metals свойства металлов

the temperature температура

industrial process промышленный процесс

2. Match the title to the text.

1. History of arc welding.
2. Generators and transformers.
3. Welding materials.
4. The arc and its characteristics features.
5. Welding shop and its operation.

3. Match the title to each paragraph.

В тексте 5 абзацев. Какие из приведенных заголовков соответствуют каждому из абзацев:
a. факторы, влияющие на качество дуги.
b. способы образования дуги.
d. характеристика дуги.
c. свойства дуги.
e. дуга – источник энергии.

Text 7

This is a story about welding materials and equipment.

Read and translate the text.

1. Welding current is conducted from the source of power to the arc by an insulated copper or aluminum cable. A very flexible cable is used between the electrode holder and the welding machine. This cable is designed for welding service.
For grounding the welding circuit, a less flexible, but equally wear resistant cable is used. The size of the cables used in welding depends upon the type of the material to be welded and the distance of the source of power.
2. The electrode is an important component of the electric circuit. We know electrodes to be divided into consumable and non-consumable electrodes. Tungsten and carbon electrodes are non-consumable. In the case of carbon and tungsten arc welding a filler metal may be fed from aside to supply an additional metal to the molten pool. As for the consumable electrodes, they are produced in the form of metal rod or wire, and for this reason provide a filler metal.
3. All the consumable electrodes are divided into bare and coated electrodes. An important advantage of arc welding is in the protection that a special mineral flux composition provides for the molten deposit. It is know that metal electrodes for the covered with flux coatings produce stronger welded joints as compared with those made with bare electrodes.
4. As it was mentioned, the electrodes are held in a special device-an electrode holder. The electrode holder is a clamping device for holding the electrode and is provided with an insulated handle for the operation’s hand. It should be mechanically strong, light in weight and hold the electrode firmly in position during welding.
5. We know that the arc is very hot and therefore it throws off both light and heat. To protect the operator’s face and eyes from the direct rays of the arc it is necessary to use a face shield or helmet. These shield or helmets are produced of pressed insulating material black in colour. The shield should be light in weight and comfortable to the welder. Shields are provided with special welding coloured lens absorbing the infrared rays, special goggles are used by welder’s assistants, foremen, inspectors and others working near the welder.
6. In addition to the equipment and materials described above, there should be available steel brushes for cleaning welds, tools for removing scale and slag from the surface of the weld and other shop equipment. Of course, in any welding shop you may find the equipment for welding inspection.

Vocabulary
Insulate – изолировать
Flexible – гибкий
Wear resistant – износостойкий
Consume – тратить, расходовать
Consumable electrode – плавящийся электрод
Composition – смесь, состав
Impurity – примесь
Float – плавить на поверхности
Eliminate – устранять, предотвращать
Handle – рукоятка
Shield – щиток (сварочный)
Helmet – шлем
Coloured – цветной

Match the title to each paragraph.
1. Electrode flux coating.
2. Electrode and their types.
3. Cables and their features.
4. Other welding equipment.
5. Protection of welder’s face and eyes.
6. Electrode holders.

Answer the questions
1. What of electrodes are applied in welding?
2. How is a filler metal provided?
3. What is the difference between the two of cables?
4. What will you say about the electrode holder?
5. How are the welder’s face and eyes protected from welding rays?
6. Say a few words about welding helmet.

4. Find the words

Insulateflexiblewearresistantimpurityfloathandlehelmetcoloured