Упражнения

1. Найдите в тексте английские эквиваленты следующих слов и словосочетаний:

1. Дуговая сварка под флюсом, 2. плавкий флюс, 3.пистолет для полуавтоматической сварки, 4. глубокое проплавление, 5. производительность \ скорость наплавки, 6. электропроводный, 7. в автоматическом режиме, 8. источник питания, 9. низколегированная сталь, 10. герметичный, 11. ленточный электрод, 12. вредный дым, 13. сила тяжести, 14. шлак, 15. удаление шлака, 16. многоточечная сварка, 17. прочный шов, 18. переменная (величина), 19. плавкий, расходуемый, 20. вредное действие атмосферы.

II. Переведите на РЯ следующие слова и словосочетания:

Carbon steel, 2. stainless steel, 3. build-up, 4. wearfacing, 5. molten weld, 6. granular flux, 7. to range, 8. wire-feeder, 9. constant current, 10. consumable electrode, 11. solid electrode, 12. application, 13. ferrous alloys, 14. residue, 15. design, 16. operating factors, 17. polarity, 18. to emit, 19. process control, 20. key variables.

Ш. Охарактеризуйте различия в семантике синонимов:

Rate – speed – velocity, to feel – to sense, application – use – usage, coal – carbon, guard – shield – protect – defend

IV. Вставьте нужное слово или словосочетание, используя содержание текста:

1. High deposition … is one of SAW advantages.

2. This process requires continuously fed … electrode.

3. SAW is normally … in the automatic or semiautomatic mode.

4. Currents … from 200 to 1500A are commonly used.

5. … current is current flowing in one direction only.

6. … current does not change its quantity.

7. Wearfacing and build-up are referred to surfacing … of SAW.

8. One of SAW advantages is that minimal welding fume or arc light is ….

9. This process is normally limited … long straight welds.

10. The molten weld and the arc zone are … from atmospheric contamination.

V. Переведите на АЯ:

1. При дуговой сварке под флюсом требуется плавкий сплошной или трубчатый электрод. 2. Шов защищен от вредного действия атмосферы флюсом. 3. Расплавленный флюс становится электропроводным. 4. Чаще всего используются источники тока с постоянным напряжением. 5. Этот метод применим лишь для сварки сплавов железа. 6. К самым важным переменным процесса относятся полярность и ток – переменный или постоянный. 7.Дуговая сварка под флюсом применяется для сварки низколегированных и нержавеющих сталей. 8. При правильном расчете и контроле за процессом получают прочные швы. 10. Результаты сварки могут зависеть от типа используемых флюса и электрода.

Unit 5. SAFETY

Users of our company’s welding equipment have the ultimate responsibility for ensuring that anyone who works on or near the equipment observes all the relevant safety precautions. Safety precautions must meet requirements that apply to this type of welding equipment. The following recommendations should be observed in addition to standard regulations that apply to the work-place.

All work must be carried out by trained personnel, well acquainted with the operation of the welding equipment, incorrect operation of the equipment may lead to hazardous situations which can result in injury to the operator and damage to the equipment.

1. Anyone who uses this welding equipment must be familiar with:

• its operation

• location of energy stops

• its function

• relevant safety precautions.

2. The operator must ensure that:

• no unauthorized person is stationed within the working area of the equipment when it is started up

• no-one is unprotected when the arc is struck.

3. The workplace must:

• be suitable for the purpose

• be free from draughts

4. Personal safety equipment:

• Always wear recommended personal safety equipment, such as safety glasses, flame-proof clothing, safety gloves

• Do not wear loose- fitting items, such as scarves, bracelets, rings, etc., which could become trapped or cause burns

5. General precautions:

• Make sure the return cable is connected securely

• Work on high voltage equipment may be carried out only by a qualified electrician

• Appropriate fire extinguishing equipment must be clearly marked and close at hand

• Lubrication and maintenance must not be carried out on the equipment during operation.

Warning

Arc welding and cutting can be injurious to yourself and others. Take precautions when welding. Ask for your employer’s safety practices which should be based on manufacturer’s hazard data.

Electric shock – can kill

• Install and earth the welding unit in accordance with applicable standards.

• Do not touch live electrical parts with bare skin, wet gloves or wet clothing.

• Insulate yourself from earth and the workpiece

• Ensure your working stance is safe.

Fumes and gases – can be dangerous to health

• Keep your head out of the fumes

• Use ventilation, extraction at the arc, or both, to take fumes and gases away from your breathing zone and the general area.

Arc rays – can injure eyes and burn skin.

- Protect your eyes and body. Use the correct welding screen and filter lens and wear protective clothing.

- Protect by-standers with suitable screens or curtains.

Fire hazard

• Sparks (spatter) can cause fire. Make sure therefore that there are no inflammable materials nearby.

Noise

• Protect your ears. Use earmuffs or other hearing protection.

• Warn by-standers of the risk.

Malfunction – call for expert assistance in the event of malfunction

VOCABULARY

Safety precautions – меры техники безопасности

Emergency stop – аварийный выключатель

Unauthorized person - посторонний

Safety glasses – защитные очки (из безосколочного стекла)

Flame-proof - негорючий

Return cable – обратный провод

Fire-extinguishing - противопожарный

Lubrication - смазка

Maintenance – техническое обслуживание

Safety practices – меры безопасности

Hazard data – сведения об авариях

To earth - заземлять

Live electrical parts – части или детали под напряжением

To insulate - изолировать

Working stance – рабочее место

Filter lens - светофильтр

Spatter – брызги (металла)

Inflammable – горючий, легко воспламеняющийся

Earmuff – беруши (приспособление для защиты от шума)

Manual – руководство, инструкция

Unit 6. SHIELDED METAL ARC WELDING

Shielded metal arc welding (SMAW), also known as manual metal arc welding (MMA) is a manual arc welding process that uses a consumable electrode coated in flux to lay the weld. An electric current, in the form of either alternating current or direct current from a welding power supply, is used to form an electric arc between the electrode and the metals to be joined. As the weld is laid, the flux coating of the electrode disintegrates giving off vapors that serve as a shielding gas and providing a layer of slag, both of which protect the weld area from atmospheric contamination.

Because of versatility of the process and simplicity of its equipment and operation, shielded metal arc welding is one of the world’s most popular welding processes. It dominates other welding processes in the maintenance and repair industry. And though flux-covered arc welding is growing in popularity, SMAW continues to be used extensively in the construction of steel structures and in industrial fabrication. The process is used primarily to weld iron and steels, including stainless steel, but aluminum, nickel and copper alloys can also be welded with this method.

To strike the electric arc the electrode is brought into contact with the workpiece in a short sweeping motion and then pulled away slightly. This initiates the arc and thus melting of the workpiece and the consumable electrode, and causes droplets of the electrode to be passed from the electrode to the welding pool. As the electrode melts, the flux disintegrates and its vapors protect the weld area from oxygen and other atmospheric gases. In addition, the flux provides molten slag which covers the filler metal as it travels from the electrode to the weld pool. Once part of the weld pool, the slag floats to the surface and protects the weld from contamination as it solidifies. Once hardened, it must be chipped away to reveal the finished weld. As welding progresses and the electrode melts, the welder must periodically stop welding to remove the remaining electrode stub and insert a new electrode into the electrode holder. This activity, combined with chipping away the slag, reduce the amount of time that the welder could spend laying the weld, making SMAW one of the least efficient welding processes. In general, the operator factor, or the percentage of operator’s time spent laying weld, is approximately 25%.

The actual welding technique utilized depends on the electrode, the composition of the work-piece, and the position of the joint being welded. The choice of electrode and welding position also determines the welding speed. Flat welds require the least operator skill, and can be done with electrodes that melt quickly but solidify slowly. This permits higher welding speeds. Sloped, vertical or upside-down welding requires more operator skill, and often necessitates the use of an electrode that solidifies quickly to prevent the molten metal from flowing out of the weld pool. However, this generally means that the electrode melts less quickly, thus increasing the time required to lay the weld.

The most common quality problems associated with SMAW include weld spatter, porosity, poor fusion, shallow penetration and cracking. Weld spatter, while not affecting the integrity of the weld, damages its appearance and increases cleaning costs. It can be caused by excessively high current, a long arc, or arc blow, a condition associated with direct current characterized by the electric arc being deflected away from the weld pool by magnetic forces. Arc blow can also cause porosity in the weld, as can joint contamination, high welding speed, and a long welding arc, especially when low-hydrogen electrodes are used. Porosity, often not visible without the use of advanced non-destructive testing methods, is a serious concern because it can potentially weaken the weld. Another defect affecting the strength of the weld is poor fusion, though it is often easily visible. It is caused by low current, contaminated joint surfaces, or the use of an improper electrode. Shallow penetration, another detriment to weld strength, can be addressed by decreasing welding speed, increasing the current or using a smaller electrode. Any of these weld-strength-related defects can make the weld prone to cracking, but other factors are involved as well. High carbon or sulfur content in the base material can lead to cracking, especially if low-hydrogen electrodes and preheating are not employed. Furthermore, the workpieces should not be excessively restrained, as this introduces residual stresses into the weld and can cause cracking as the weld cools.

SMA welding, like other welding methods, can be a dangerous and unhealthy practice if proper precautions are not taken. The process uses an open electric arc, presenting a risk of burns which is prevented by personal protective equipment in the form of heavy leather gloves and long sleeve jackets. Additionally, the brightness of the weld area can lead to a condition called arc eye, in which ultraviolet light causes the inflammation of the cornea and can burn the retinas of the eyes. Welding helmets with dark face plates are worn to prevent this exposure, and in recent years, new helmet models have been produced featuring a face plate that self-darkens upon exposure to high amounts of UV light. To protect by-standers, especially in industrial environments, transparent welding curtains often surround the welding area. These curtains, made of polyvinyl chloride plastic film, shield nearby workers from exposure to the UV light from the electric arc, but should not be used to replace the filter glass used in helmets.

In addition, the vaporizing metal and flux materials expose welders to dangerous gases and particulate matter. The smoke produced contains particles of various types of oxides. The size of the particles in question tends to influence the toxicity of the fumes, with smaller particles presenting a greater danger. Additionally, gases like carbon dioxide and ozone can form, which can prove dangerous if ventilation is inadequate.

VOCABULARY

SMAW – shielded metal arc welding – дуговая сварка металлическим электро-

дом в защитной среде

Consumable electrode – плавящийся электрод

To disintegrate – разлагаться, распадаться

To give off – зд. выделять

Versatility – зд. многофункциональность

Maintenance – тех.обслуживание

Flux-cored electrode – фитильный электрод с флюсом

To strike the arc – включить, зажечь дугу

Molten slag – расплавленный шлак

To solidify - застывать

To chip away - скалывать

Stub – огарок электрода

Industrial fabrication – промышленное производство

To initiate – вызывать, начинать

Filler metal – наплавочный металл

Electrode holder – держатель электрода

Composition - состав

Weld spatter - брызги (металла при сварке)

Penetration – глубина проплавления

High current – ток большой величины

Arc blow – уход, сдвиг дуги

To deflect – отклоняться, уходить в сторону

Restrain - зажимать

Residual stress – остаточное напряжение

Arc eye – ослепление от света дуги, «сварки нахвататься»

Cornea – роговица глаза

Retina – сетчатка (глаза)

Filter glass - светофильтр

Welding helmet – маска, шлем (сварщика)

Particulate matter – мелкие частицы

Clamp - зажим

Welding lead – питающий провод

Arc distance/length – расстояние \ длина дуги

Fluctuations – отклонения, колебания