Vocabulary

coalescence соединение, слипание, сращение

molten pool ванна расплавленного металла, сварочная ванна

gas flame газовое пламя

solid-phase твёрдая фаза

ultrasonic ультразвуковой

friction трение

furnace печь

diffusion 1) рассеивание 2) диффузия

high-current сильноточный

low-voltage низковольтный, низкого напряжения

discharge разряд

arc column столб дуги

direct current (dc) постоянный ток

alternating current (ac)переменный ток

layer слой, пласт, ряд

molten-metal

droplet

капля жидкого металла

inert atmosphere инертная среда

annulus тех. узкое кольцо (зазор и т. п.)

torch сварочная горелка (для автоматической сварки –

головка)

base metal основной металл

grain зерно

precipitation осаждение

residual stress остаточное напряжение

5. Find the English equivalents for the following words and word combinations.

Расплавленный металл, необходимый размер, не нагретый металл, механические свойства, максимум температуры, защищать поверхности, быстрое охлаждение, осуществлять контроль, препятствовать окислению, вступать в химическую реакцию, термообработка, бомбардировка электронами, зона термического [теплового] воздействия, общая потребляемая энергия.

6. Complete the following sentences.

1. A characteristic feature of fusion welding is:

a) molten metal b) low-voltage discharge c) inert atmosphere

2. Furnace heating is usually employed in

a) friction joining b) diffusion bonding c) ultrasonic joining

3. The consumable electrode is made

a) negative b) positive c) neither

4. Total energy input in all welding processes is

a) is greater than required to produce a joint b) is smaller than required

to produce a joint c) equals to required to produce a joint

5. Reactions of most metals with the atmosphere or other nearby metals can

1) improve the properties of a welded joint b) make the properties of a

welded joint worse c) never influence the properties of a welded joint

6. The most common gas used in gas-shielded metal-arc and gas-shielded

tungsten-arc welding is

a) argon b) oxygen c) carbon dioxide

7. If not controlled, residual stress results in

a) precipitation processes in welded structures, b) freezing of the weldmetal

c) bowing or distortion of the weldment.

7. Say if the following sentences are true or false.

1. There is always a welding pool in solid-phase welding processes.

2. Total energy input in all welding processes is greater than needed to produce a weld.

3. Reactions of metals with the atmosphere or other nearby metals are favorable to the properties of a welded joint.

4. Fluxes and inert atmospheres play a protective role and prevent oxidation.

5. The heat-affected zone is a region with unaltered properties.

6. Residual stress is present in all welded structures.

8. Write a short report on the subject below.

Function of Fluxes and Inert Atmosphere in Welding

9. Study the Master Chart of the Principal Welding Processes (Chart

1) and complete the sentences.

1. The two basic welding processes are ... .

2. The fusion processes consist of … .

3. Among these, arc welding can be accomplished …

4. Arc welding with consumable electrodes includes the following types… .

5. Carbon arc welding, atomic hydrogen welding, inert gas tungsten arc

welding refer to … .

10. Describe the classification of pressure processes. Use the verbs in bold from the previous exercise.

11. Look through the text. Make a short summary of it.

Alternative Types of Welding

Cold welding

Cold welding, the joining of materials without the use of heat, can be

accomplished simply by pressing them together. Surfaces have to be well

prepared, and pressure sufficient to produce 35 to 90 percent deformation at

the joint is necessary, depending on the material. Lapped joints in sheets and

cold-butt welding of wires constitute the major applications of this

technique. Pressure can be applied by punch presses, rolling stands, or

pneumatic tooling. Pressures of 1,400,000 to 2,800,000 kilopascals (200,000

to 400,000 pounds per square inch) are needed to produce a joint in

aluminum; almost all other metals need higher pressures.

Friction welding

In friction welding two work pieces are brought together under load

with one part rapidly revolving. Frictional heat is developed at the interface

until the material becomes plastic, at which time the rotation is stopped and

the load is increased to consolidate the joint. A strong joint results with the

plastic deformation, and in this sense the process may be considered a

variation of pressure welding. The process is self-regulating, for, as the

temperature at the joint rises, the friction coefficient is reduced and

overheating cannot occur. The machines are almost like lathes in appearance.

Speed, force, and time are the main variables. The process has been

automated for the production of axle casings in the automotive industry.

Laser welding

Laser welding is accomplished when the light energy emitted from a

laser source focused upon a work-piece to fuse materials together. The

limited availability of lasers of sufficient power for most welding purposes

has so far restricted its use in this area. Another difficulty is that the speed

and the thickness that can be welded are controlled not so much by power but

by the thermal conductivity of the metals and by the avoidance of metal

vaporization at the surface. Particular applications of the process with very

thin materials up to 0.5 mm (0.02 inch) have, however, been very successful.

The process is useful in the joining of miniaturized electrical circuitry.

Diffusion bonding

This type of bonding relies on the effect of applied pressure at an

elevated temperature for an appreciable period of time. Generally, the

pressure applied must be less than that necessary to cause 5 percent

deformation so that the process can be applied to finished machine parts. The process has been used most extensively in the aerospace industries for joining

materials and shapes that otherwise could not be made—for example,

multiple-finned channels and honeycomb construction. Steel can be

diffusion bonded at above 1,000 ° C (1,800 ° F) in a few minutes.

Ultrasonic welding

Ultrasonic joining is achieved by clamping the two pieces to be welded

between an anvil and a vibrating probe or sonotrode. The vibration raises the

temperature at the interface and produces the weld. The main variables are

the clamping force, power input, and welding time. A weld can be made in

0.005 second on thin wires and up to 1 second with material 1.3 mm (0.05

inch) thick. Spot welds and continuous seam welds are made with good

49

reliability. Applications include extensive use on lead bonding to integrated

circuitry, transistor canning, and aluminum can bodies.

Explosive welding

Explosive welding takes place when two plates are impacted together

under an explosive force at high velocity. The lower plate is laid on a firm

surface, such as a heavier steel plate. The upper plate is placed carefully at an

angle of approximately 5° to the lower plate with a sheet of explosive

material on top. The charge is detonated from the hinge of the two plates, and

a weld takes place in microseconds by very rapid plastic deformation of the

material at the interface. A completed weld has the appearance of waves at

the joint caused by a jetting action of metal between the plates.