I. Переведите предложения, обращая внимание на перевод объектного и субъектного инфинитивного оборота.

1. Everybody was waiting for him to announce it. 2. We may expect a short circuit to result from wire fault. 3. Everybody is certain to know that alternating voltage can be increased and decreased. 4. A fuse is expected to melt and break the circuit. 5. He is said to be working on his report.

II. Переведите предложения, обращая внимание на перевод зависимого и независимого причастного оборота.

1.  Industrial applications of energy increasing, more and more energy is needed every year. 2. The method being used by this engineer is very effective. 3. The experiment having been finished, the scientist published the results. 4. The engineer testing the engine is a good specialist. 5. I've just had my suit cleaned. III. Переведите предложения, обращая внимание на перевод условных предложений.

1. Do you ever wish you could fly? 2. If you were in my position, what would you do? 3. I decided to stay at home last night. I would have gone out if I hadn't been so tired. 4. I'll come tomorrow unless I have to work. 5. You might have seen him yesterday if you had called at seven.

IV. Прочитайте и письменно переведите следующий текст. Письменно ответьте на вопросы к тексту.

 

Basic principles of welding

A weld can be defined as a coalescence of metals pro­duced by heating to a suitable temperature with or with­out the application of pressure, and with or without the use of a filler material.

In fusion welding a heat source generates sufficient heat to create and maintain a molten pool of metal of the required size. The heat may be supplied by electricity or by a gas flame. Electric resistance welding can be consid­ered fusion welding because some molten metal is formed.

Solid-phase processes produce welds without melting the base material and without the addition of a filler metal. Pressure is always employed, and generally some heat is provided. Frictional heat is developed in ultra­sonic and friction joining, and furnace heating is usu­ally employed in diffusion bonding.

The electric arc used in welding is a high-current, low-voltage discharge generally in the range 10-2,000 am­peres at 10-50 volts. An arc column is complex but, broadly speaking, consists of a cathode that emits elec­trons, a gas plasma for current conduction, and an anode region that becomes comparatively hotter than the cath­ode due to electron bombardment.

Most metals, when heated, react with the atmosphere or other nearby metals. These reactions can be extremely detrimental to the properties of a welded joint. Most metals, for example, rapidly oxidise when molten. A layer of oxide can prevent proper bonding of the metal. Molten-metal droplets coated with oxide become en­trapped in the weld and make the joint brittle. Some valu­able materials added for specific properties react so quickly on exposure to the air that the metal deposited does not have the same composition as it had initially. These problems have led to the use of fluxes and inert atmospheres.

In fusion welding the flux has a protective role in fa­cilitating a controlled reaction of the metal and then pre­venting oxidation by forming a blanket over the molten material. Fluxes can be active and help in the process or inactive and simply protect the surfaces during joining.

Inert atmospheres play a protective role similar to that of fluxes. In gas-shielded metal-arc and gas-shielded tungsten-arc welding an inert gas – usually argon – flows from an tube surrounding the torch in a continuous stream, displacing the air from around the arc. The gas does not chemically react with the metal but simply pro­tects it from contact with the oxygen in the air.

Questions:

1. How can a process of welding be defined? 2. What are the main groups of processes of welding? 3. What does an arc column consist of? 4. What are the principles of gas welding?

1.2.4.3. Вариант № 3