Урок 4 Тема. Чёрные и цветные сплавы

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Название	Урок 4 Тема. Чёрные и цветные сплавы
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Тип	Урок

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Тема. Сварка (продолжение).

Грамматика. Participle II в функции обстоятельства с предшествующими союзами (повторение).
Упр. 1. Прочитайте следующие слова и выражения. Какие русские слова они вам напоминают?

actual, inspection, design, ionized gas, base metal, chemical composition, specified, ionic.
Упр. 2. При помощи суффикса – en образуйте глаголы от следующих прилагательных. Переведите на русский язык.
black a – чёрный

blacken v – делать чёрным
deep, wide, weak, short, hard, thick,
Упр. 3. Переведите следующие словосочетания:

a film of oxides

to weaken the weld

a source of a filler metal

a stream of an ionized gas

high-speed cutting

by the way

the presence of impurities

considerable internal stresses

the purpose of heat treatment

to improve the structure

welded structures

Упр. 4. Переведите предложения, обращая внимание на Participle II в функции обстоятельства с предшествующими союзами: when, while – когда; if – если; unless – если ... не; until – пока ... не;

When heated to 100⁰С water boils.

При нагревании до 100⁰С вода кипит.

Когда воду нагревают до 100⁰С, она кипит.

Unless heated to a definite temperature metals do not melt.

Без нагревания до определённой температуры металлы не плавятся.

Если металлы не нагревать до определённой температуры, они не плавятся.

When used fluxes melt in the heat of the arc.
Unless acted upon by some external force the parts to be welded by resistance welding can't be joined.
Until cleaned, two workpieces couldn't be properly welded.
If selected the welding torch for welding particular workpieces should be the lightest equipment which will do the job satisfactorily.
Unless selected properly a filler metal can reduce the strength of the weld.
If applied a filler wire should be cleaned as thoroughly as the weld joints.
Unless removed after welding fluxes can cause corrosion of the weld and the base metal.
When applied the welding robot "Sever" welds the pipes ten times faster than a team of 12 welding operators.
Until tested welded pipelines cannot be put into operation.

Упр. 5. Слова к тексту “Welding” (Part II).

1. preparatory [prI'pxrqtqrI] a	подготовительный A lot of preparatory work must be done before welding.
2. precede [prJ'sJd] v	предшествовать Cleaning precedes welding.
3. actual ['xktjuql] a	действительный, фактический, актуальный Actual data were obtained by complex calculations.
4. choice [COIs] n	выбор The choice of a welding technique depends on many factors.
5. joint ['GOInt] n	стык, соединение Brazed joints in aluminium alloys have a good resistance to corrosion.
6. moreover [mL'rouvq] adv	более того Moreover, brazed joints in aluminium alloys possess good strength.
7. consumable [kqn'sjHmqbl] a	зд. плавящийся The composition of consumable electrodes must be similar to the composition of the metals to be welded.
8. nonconsumable a	зд. неплавящийся Tungsten is widely used for nonconsumable electrodes.
9. shield [SJld] v	защищать As with other reactive metals, in welding zirconium must be shielded from air.
10. shielding n	защита The shielding of the zirconium weld must be made with very pure argon, helium or a mixture of these two.
11. shielding a	защитный Zirconium can be welded with tungsten electrodes in the environment of shielding (inert) gases, filler metal being zirconium or one of its alloys.
12. separately ['sep(q)rItlI] adv	отдельно Aluminium and some semiconductors such as graphite and magnetite must be kept separately as in contact with them aluminium corrodes.
13. melt v (through)	проплавлять The welder should be very careful not to melt through the whole thickness of the metal otherwise the structure can break.
14. tough [tAf] a	жёсткий, прочный Austenitic stainless steels are both tough and ductile.
15. manual ['mænjuql] a	ручной Manual welding of pipelines in the past often resulted in failures.
16. hardfacing n	наплавка твёрдым сплавом Titanium carbides are often used for hardfacing new and worn parts to increase their resistance to wear.
17. penetrate ['penItreIt] v	проникать In liquid corrosion monitoring a liquid penetrates into any defects open at the surface and then a coloured powdered material is applied on the surface.
18. penetrating a	проникающий The penetrating rate in turbo-drilling is faster than the one in conventional rotary drilling.
19. red shortness n	красноломкость Red shortness is a negative structural phenomenon of steels which leads to failures of constructions.
20. deteriorate [dI'tIqrIqreIt] v	ухудшать(ся) Even a properly applied coating of paint does not last forever. It breaks down and deteriorates within a year or so due to the effect of the environment.
21. weldability ["weldq'bIlItI] n	свариваемость Weldability of steels can be improved by removing exceeding amounts of carbon, phosphorus and sulphur.
22. predetermined ['prJdI'tWmInd] a	заранее определённый The colour of your eyes is predetermined by the colours of you parents’ eyes.
23. hold (held, held) v	зд. выдерживать The dam wasn’t strong enough to hold the flood waters.
24. relieve [rI'lJv] v	облегчать, уменьшать The corrosion rate of aluminium coupled to copper in seawater is relieved greatly when the seawater is deaerated.
25. ultrasonic ["Altrq'sOnIk] a	ультразвуковой Ultrasonic testing is a nondestructive method of determining wall thickness or the location of defects within any material capable of conducting sound.
26. prescribed [prIsk'raIbd] period of time	заранее определённый период времени Smelting of both ferrous and non-ferrous metals is performed for a prescribed period of time.
27. to refine the grain	улучшать структуру Heat treatment of stainless steels is employed to refine their grains, for them to meet special conditions and to be used for special applications.
28. submerged [sqb'mWGd] arc welding	дуговая сварка под флюсом
29. (gas) shielded metal arc welding	дуговая сварка металлическим электродом в среде защитного газа
30. inert-gas tungsten-arc welding	дуговая сварка вольфрамовым электродом в среде инертного газа
31. electron beam welding	электроннолучевая сварка
32. laser ['leIzq] (beam) welding	лазерная сварка

Прочитайте текст “Welding” (Part II). Выполните следующие задания.

Скажите, какие подготовительные шаги нужно предпринять, чтобы сварочный шов был хорошего качества.
Найдите в тексте случаи употребления Participle II с предшествующими союзами.

Welding (Part II)
The preparatory steps which precede actual welding are significant to any successful welding operation. Such things must be considered as a welding method to be used, the choice of the base and filler metals, the actual joint design and often the inspection methods which are to be used.

The proper cleaning of the surfaces to be joined is one of the main conditions for obtaining high-quality welds in the majority of welding processes. Moreover, the heating of metals to a high temperature causes oxidation and a film of oxides is formed on the heated surfaces that weakens the weld. To avoid it, a flux is applied to the heated metal. At the welding heat the flux melts, and the oxide particles are dissolved in it together with any other impurities which may be present. Fluxes are used in submerged arc welding. The inventor of this method was a Russian engineer N.G. Slavjanov who first demonstrated this method as early as 1888. He was the first to use consumable electrodes.

Another way to obtain a sound weld is to weld metals in the environment of inert gases, mainly argon or helium or their mixture. These gases are called shielding gases. When used shielding gases improve the quality of the weld as well.

Shielding gases may be used in arc processes, with both consumable and nonconsumable electrodes being applied. Consumable electrodes serve both as conductors of electricity and a source of a filler metal. An example of this process is gas-shielded metal-arc welding.

In welding processes with nonconsumable electrodes the conductor of electricity is a metal electrode and a filler metal is provided separately. Inert-gas tungsten-arc welding in which a tungsten electrode is used is an example of this process. It was introduced in the 40's for welding magnesium. Nowadays it is of great significance for welding not only magnesium but also aluminium, titanium, stainless steels.

Later plasma arc welding was developed. It is a kind of inert-gas-shielding processes. Plasma is a stream of ionized gas. It is so hot and dense that it melts through thick metals and works efficiently on even the toughest alloys. Plasma welding can be used on the materials that do not conduct electricity. This method is used not only for welding but also for cutting aluminium and stainless steels, as well as for high-speed cutting of carbon steels. By the way, different welding processes can be used for cutting metals and for hardfacing.

There are some more melting processes which are certain to play important roles in years to come. In electron beam welding a stream of electrons is focused on the welding zone. The beam has a great penetrating power, it can be used to weld almost any metal, in almost any thickness.

In laser beam welding a beam of light is used instead of a beam of electrons. Like the electron beam, this light has a great penetrating power.

As mentioned above one of the preparatory steps which preceeds actual welding is the choice of a base metal and a filler metal. A sound weld can be obtained when the base metal possesses good weldability which is affected by the chemical composition of the metal, its physical properties, the degree of alloying, the presence of impurities and the heat treatment to which it is subjected. So before welding one must know all these data and choose the filler metal of the proper composition.

The following elements present in the base metal if they exceed the permissible amounts can deteriorate the weldability of steels. Carbon if it exceeds 0.3 per cent causes brittleness of the weld. Phosphorus in amounts more than 0.04 per cent increases brittleness as well. The sulphur content being over 0.04 per cent, red shortness is caused.

The concentration of heat in a small area in welding can lead to considerable internal stresses. To avoid it heat treatment is used. Heat treatment is a very important engineering process. The purpose of heat treatment is to improve the structure of steel and to obtain higher or specified mechanical properties. The metal structure is changed by means of 3 techniques, i.e.:1) heating the metal to a predetermined temperature; 2) holding it at this temperature for a prescribed period of time and at last 3) cooling it at a prescribed rate. The types of heat treatment applied in practice are: 1) annealing, 2) normalization, 3) hardening and 4) tempering.

If applied heat treatment relieves internal stresses in the metal, refines the grain and reduces hardness. The metals become more plastic and ductile.

After welding welded structures should be inspected to avoid failures. There are different ways of welds inspection, among them radiography (using highly penetrating X-rays and gamma rays), ultrasonic testing, electrical resistance principle.

It should be mentioned that due to the development of new branches of industry new welding processes are being developed and introduced successfully, e.g. ionic, diffusion, ultrasonic, electromagnetic processes and others.

In conclusion it should be noted that there are manual, semi-automatic and automatic welding processes.

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