Exercise 3 Based on what you have read, match each of the arc welding methods with its description
| · Submerged arc welding · Shielded metal arc welding · Gas metal arc welding · Gas tungsten arc welding | a) It’s a manual welding process that uses a nonconsumable tungsten electrode, an inert or semi-inert gas mixture and a separate filler material. b) It’s a semi-automatic or automatic process that uses a continuous wire feed as an electrode and an inert or semi-inert gas mixture to protect the weld from contamination. c) It’s a high-productivity welding method in which the arc is struck beneath a covering layer of flux. d) One of the most common types of arc welding which is also known as manual metal arc welding or stick welding. |
Exercise 4 Find sentences with Modal verbs in the text. Translate them into Ukrainian. Write these sentences in Past and Future Tenses.
Exercise 5 Match the symbols of arc welding hazards with their meaning.
a) 
b) 
c) 
d)
| 1 Hot parts can cause severe burns. 2 Electric shock can kill. 3 Arc rays can burn eyes and skin. 4 Welding can cause fire or explosion. |
UNIT 6
Exercise 1 Scan the text to find what gas welding methods were described in the text:
Gas welding
The most common gas welding process is oxyfuel welding, also known as oxyacetylene welding. It is one of the oldest and most versatile welding processes, but in recent years it has become less popular in industrial applications. It is still widely used for welding pipes and tubes, as well as repair work. It is also frequently well-suited, and favoured, for fabricating some types of metal-based artwork. Oxyfuel equipment is versatile, lending itself not only to some sorts of iron or steel welding but also to brazing, braze-welding, metal heating (for bending and forming), and also oxyfuel cutting. The equipment is relatively inexpensive and simple, generally employing the combustion of acetylene in oxygen to produce a welding flame temperature of about 3100 °С. The flame, since it is less concentrated than an electric arc, causes slower weld cooling, which can lead to greater residual stresses and weld distortion, though it eases the welding of high alloy steels. A similar process, generally called oxyfuel cutting, is used to cut metals. Other gas welding methods, such as air acetylene welding, oxygen hydrogen welding, and pressure gas welding are quite similar, generally differing only in the type of gases used. A water torch is sometimes used for precision welding of small items such as jewellery.
Gas welding is also used in plastic welding, though the heated substance is air, and the temperatures are much lower.
Exercise 2 Comprehension questions:
1 What is gas welding? How os it performed?
2 What fuels are used in gas welding?
3 How is the gas welding torch designed?
4 What equipment is used for oxyfuel welding?
5 What temperatures are used for different methods of gas welding?
Exercise 3 Find in the text sentences with adjectives. Translate these sentences into Ukrainian. Make up sentences of your own, using these adjectives in the positive, the comparative and the superlative degrees.
Exercise 4 Give Ukrainian equivalents of the following gas welding methods and terms:
· oxyfuel welding/ oxyacetylene welding;
· combustion of acetylene in oxygen;
· weld cooling;
· weld distortion;
· alloy steel;
· oxyfuel cutting;
· air acetylene welding;
· oxygen hydrogen welding;
· pressure gas welding;
· a water torch;
· plastic welding.
Exercise 5 Put the following sentences in the negative and the interrogative forms. Translate them:
1 The heated edges are fused without the deposit of metal.
2 All gas welding processes utilize oxygen combined with acetylene and other fuels.
3 Oxyacetylene welding has become less popular in industrial applications in recent years.
4 Oxyfuel welding is one of the oldest and most versatile welding processes.
UNIT 7
Exercise 1 Scan the text for answering the question: What is resistance welding used for?
ELECTRIC WELDING
This type of welding is a pressure process, as is forge welding. It consists of heating to their plastic temperature the surfaces of parts to be joined, then applying pressure mechanically to achieve complete union of the parts. The heating is accomplished by passage of a heavy, localized electric current. Alternating current of common commercial voltage is employed for this purpose.
In all types of resistance welding, selection of proper electrodes is important to the success of the process. Electrodes must possess a high degree of thermal and electrical conductivity, and they also must possess strength and hardness.
Small pools of molten metal are formed at the weld area as high current (1000-100,000 A) is passed through the metal. In general, resistance welding methods are efficient and cause little pollution, but their applications are somewhat limited and the equipment cost can be high.
Types of resistance welding are: spot welding; butt welding; flash welding; percussion welding; seam welding; projection welding.
Spot Welding.— Spot welding is a popular resistance welding method used to join overlapping metal sheets of up to 3 mm thick. Two electrodes are simultaneously used to clamp the metal sheets together and to pass current through the sheets. The advantages of the method include efficient energy use, limited workpiece deformation, high production rates, easy automation, and no required filler materials. Weld strength is significantly lower than with other welding methods, making the process suitable for only certain applications. It is used extensively in the automotive industry—ordinary cars can have several thousand spot welds made by industrial robots.
A spot-welding machine is the simplest form of resistance-welding device; therefore it is widely adapted throughout the metal-working industry.
Butt-Welding.— By this process the parts to be welded are gripped 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, bars, rods, light- and medium-weight structural shapes, etc., may be butt welded.
Flash Welding.— This is another type of butt welding, the difference consisting in the method of heating the base metals. The electrodes are clamped to the parts to be joined, and a heavy current is passed through them. The movable electrode brings the surface of the metal it holds into contact with the surface of the metal held in the stationary electrode. Just before the two pieces meet, an arc developed in the short gap causes sufficient heat to make the surface to be joined plastic.
Percussion Welding.— This process is similar to flash welding inasmuch as it relies upon a sudden discharge of electrical energy (produced by the arc) at the joint to generate sufficient heat to make the surfaces to be joined plastic. The pressure required to accomplish the weld at the proper moment is obtained by employing a heavy spring.
Seam Welding.— This is a resistance-welding process which consists of passing two or more base metals between electrodes which are in the form of rollers. 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. The welded joint thus produced is similar to a seam made in cloth.
Refrigerators, metal containers, gasoline tanks, automobile mufflers, aircraft fabrications, pipes for furnaces and stoves, and other products requiring pressure-tight seams are rapidly produced by seam welding.
Projection Welding.— This process is similar to spot welding and 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.
The current and pressures required for this type of welding are heavier than those applied in spot welding. Various sheet-metal parts used in automobile and aircraft production are welded by this process.
Electric Arc Welding.— This is a fusion-welding process in which surfaces to be joined are fused by the heat of an electric arc. By bringing the work and the electrode together as conductors, an electric circuit is established; then, by separating the conductors, an electric arc is created in which the electrical energy is converted into heat.
Exercise 2 Comprehension questions:
1 What is electric welding?
2 What electric current is employed for electric welding?
3 What types of resistance welding are described in the text?
4 What type of resistance welding is used in the automotive industry?
5 What was seam welding used for in the past and what is it used for nowadays?
Exercise 3 Find in the text English equivalents to the following:
Електрозварка, електричний ток, звичайна промислова напруга, термоелектричнопровідність, точкова зварка, рель‘єфна зварка, нерухомий електрод, зварка методом опору, шов в матерії, деталі із листового заліза, елеткродуга.
Exercise 4 Match each of the following electrical welding methods with its descriptions:
| · Projection welding · Butt-welding · Percussion welding · Spot welding · Electrical arc welding · Seam welding · Flash welding | a) This process consists of holding two or more metals between suitable electrodes which pass a heavy current through the materials to be welded; b) This process consists of joining two pieces of metal one or both of which have mechanically formed projections; c) By this process the parts to be welded are crippled mechanically and pressed together while heat is generated by passage of a heavy current through the area of joint; d) This process relies upon a sudden discharge of electrical energy at the joint to generate sufficient heat to make the surfaces to be joined plastic; e) This is a fusion-welding process in which surfaces to be joined are fused by the heat of an electric arc; f) This process consists of passing two or more base metals between electrodes which are in the form of rollers; g) This is another type of butt-welding, the difference consisting in the method of heating the base metals. |
Exercise 5 Put 5 questions to the sentence:
Resistance welding involves the generation of heat by passing current through the resistance.
UNIT 8
Exercise 1 Read and translate the texts:
Energy beam welding
Energy beam welding methods, namely laser beam welding and electron beam welding, are relatively new processes that have become quite popular in high production applications. The two processes are quite similar, differing most notably in their source of power. Laser beam welding employs a highly focused laser beam, while electron beam welding is done in a vacuum and uses an electron beam. Both have a very high energy density, making deep weld penetration possible and minimizing the size of the weld area. Both processes are extremely fast, and are easily automated, making them highly productive. The primary disadvantages are their very high equipment costs (though these are decreasing) and a susceptibility to thermal cracking. Developments in this area include laser-hybrid welding, which uses principles from both laser beam welding and arc welding for even better weld properties.
Solid-state welding
Like the first welding process, forge welding, some modern welding methods do not involve the melting of the materials being joined. One of the most popular, ultrasonic welding is used to connect thin sheets or wires made of metal or thermoplastic by vibrating them at high frequency and under high pressure. The equipment and methods involved are similar to that of resistance welding, but instead of electric current, vibration provides energy input. Welding metals with this process does not involve melting the materials; instead, the weld is formed by introducing mechanical vibrations horizontally under pressure. When welding plastics, the materials should have similar melting temperatures, and the vibrations are introduced vertically. Ultrasonic welding is commonly used for making electrical connections out of aluminum or copper, and it is also a very common polymer welding process.
Another common process, explosion welding, involves the joining of materials by pushing them together under extremely high pressure. The energy from the impact plasticizes the materials, forming a weld, even though only a limited amount of heat is generated. The process is commonly used for welding dissimilar materials, such as the welding of aluminum with steel in ship hulls or compound plates. Other solid-state welding processes include co-extrusion welding, cold welding, diffusion welding, friction welding (including friction stir welding), high frequency welding, hot pressure welding, induction welding, and roll welding.
Exercise 2 Comprehension questions:
1 What is similar and different between laser beam welding and electron beam welding?
2 What are disadvantages of both these methods?
3 What is ultrasonic welding used for?
4 How is ultrasonic welding performed?
5 What is explosion welding and what is it used for?
Exercise 3 Give Ukrainian equivalents of the following:
· laser beam welding;
· electron beam welding;
· high energy density;
· weld penetration;
· thermal cracking;
· laser-hybrid welding;
· solid-state welding;
· ultrasonic welding;
· explosion welding.