Введение
Учебное пособие предназначено для студентов 2 курса очного и заочного отделений, обучающихся по направлению 15.03.01 Машиностроение, профиль: «Оборудование и технология сварочного производства».
Пособие состоит из введения, 4 тематических блоков, включающих в себя темы соответствующие уровням подготовки студентов (основной, повышенный), видеоматериалов, заданий для самостоятельной работы студентов.
Каждый блок содержит аутентичный текстовый материал профессиональной направленности, соответствующий вышеуказанным профилям, комплекс речевых упражнений.
Представлены предтекстовые и послетекстовые упражнения. Предтекстовые задания ориентированы на введение ключевых слов и словосочетаний, терминов путем выполнения задания на нахождение соответствий между английским словом и его значением на русском языке.
Послетектовые упражнения направлены на развитие умений поиска специальной информации по прочитанному тексту и предусматривают выполнение заданий на заполнение пропусков в предложенных предложениях, ответы на вопросы по содержанию текста. Большое внимание уделено активизации лексического материала в речевых высказываниях по изучаемой тематике путем выполнения заданий на выбор правильных или неправильных утверждений с последующей аргументацией, в обсуждении прочитанного материала в группах.
Применение ИКТ (видео, интернет-ресурсы) в данном учебном пособии способствует более эффективному изучению предметной области на иностранном языке.
В пособии также предусмотрен блок для дополнительный текстов для самостоятельного чтения, перевода, реферирования и аннотирования текстов.
Автор выражает признательность Филиновой Елене Федоровне за материалы использованные при создании данного учебного пособия.
Content
| стр. | |
| Введение | 4 |
| Содержание | 5 |
| Unit 1 | 6 |
| Text 1. METALS AND THEIR PROPERTIES | 6 |
| Text 2. IRON AND STEELS | 10 |
| Video “How to Make Steel” | 13 |
| Text 3. THE IRON PILLAR FROM DELHI | 15 |
| Unit 2 | 17 |
| Text 1. THE WORLD OF WELDING | 17 |
| Text 2. WELDING | 19 |
| Text 3. HISTORY OF WELDING | 21 |
| Text 4. HISTORY OF WELDING IN THE BEGINNING | 24 |
| Unit 3 | 27 |
| Text 1. FORGE WELDING (PART 1) | 27 |
| Text 2. FORGE WELDING (PART 2) | 29 |
| Video “MIG Welding” | 32 |
| Text 3. ARC WELDING (1) | 33 |
| Video “How to Become an Electric Arc Welder” | 34 |
| Text 4. ARC WELDING (2) | 36 |
| Unit 4. | 38 |
| Text 1. CLASSIFICATION OF WELDING | 38 |
| Text 2. SHIELDED METAL ARC WELDING | 42 |
| Text 3. FIND OUT MORE ABOUT RESISTANCE WELDING AND ITS TYPES | 45 |
| Text 4. SPOT WELDING | 46 |
| Video “Resistance Welding” | 48 |
| Text 5. SEAM WELDING | 51 |
| Supplementary Texts | 53 |
| Список литературы | 63 |
UNIT 1.
| 1. Basic Level Text 1. METALS AND THEIR PROPERTIES 2. Higher level Text 2. IRON AND STEELS 3. Grammar: the Infinitive; as well as, rather than, in order to. 4. Video: HOW TO MAKE STEEL 5. Individual work Text 3. THE IRON PILLAR FROM DELHI |
Basic Level:
Exercise 1. Answer the following questions. Use the background knowledge.
a) What are metals?
b) What are the most valuable metal properties?
c) What metals are called common/ precious / rare?
d) Can you remember the most popular application areas of metals?
e) What role do metals play in our country?
Exercise 2.Give Russian equivalents to the following:
| · Chemical element | · To conduct |
| · Periodic Table | · Concentration |
| · Hammer | · Electricity |
| · Non-metals | · Basis |
| · Heat | · Volume |
| · Electrolysis | · Bone |
| · Mixture | · Strong |
Exercise 3. Read the words aloud. Pay attention to your pronunciation.
Luster, hydrogen, copper, ductile, gravity, pure, mixture, chemistry, liquid, malleable, alloy, potassium, lead, ancient, hafnium, characteristic, ornament, machine.
Exercise 5. Fill in the gaps in the table.
| Noun | Adjective | Verb | Adverb |
| gas | Gaseous | - | - |
| Brittle | |||
| To conduct | |||
| Essentially |
Exercise 10. Say what do you know about (i) steel, (ii) steel-making process, (iii) steel-making enterprises in Udmurtia, (iv) the role of Russia in world’s steel production. Give your answer in the form monologue / dialogue / group presentation.
Higher Level:
Text 2. Iron and Steels
Iron is an incredibly useful substance. It's less brittle than stone yet, compared to wood or copper, extremely strong. If properly heated, iron is also relatively easy to shape into various forms, as well as refine, using simple tools. There certainly aren't any iron shortages to worry about. The Earth's crust is 5 percent iron, and in some areas, the element concentrates in ores that contain as much as 70 percent iron.
Very pure iron is prepared by reducing ferric oxide with hydrogen at 1,000 degrees C or by vacuum melting of a product obtained by electrolysis of ferrous ammonium sulphate solution. Chemically pure iron is produced by thermal decomposition of iron pentacarbonyl at 200 to 250 degree C, when iron is deposited as a fine powder.
Physical Properties of Iron. Pure iron is a grayish-white soft metal. Its melting point and boiling point are 1,538 degree C and 2,735 degree C respectively. Pure iron is malleable and ductile and does not harden on quenching. It is more magnetic than any other metal, and its magnetic properties remain unaffected even at a very high temperature. Iron is a good conductor of heat and electricity.
Pure iron exists in three allotropic forms, depending on temperature. These are distinguished as α-, γ- and δ-iron respectively. These differ in their thermal stability, crystal structure, hardness, magnetic properties and in their ability to dissolve carbon.
Chemical Properties of Iron. Pure iron is unaffected by dry air and pure water at ordinary temperature, but commercial iron rusts in moist air and water. Pure iron gives off hydrogen, nitrogen and carbon monoxide on heating. The metal burns brilliantly when heated in oxygen and also undergoes combustion in burning sulfur. It decomposes steam at red heat, which is utilized in the manufacture of hydrogen.
Steel is the most important form of commercial iron. Steel is manufactured by blending carbon and iron in a specified ratio, where the normal percentage of carbon ranging from 0.2 to 2.14 per cent of the total weight. Apart from carbon, the other alloying materials used in the production of steel include manganese, chromium, tungsten and vanadium which impart desired properties to the steel. This metal has a wide range of properties.
The properties of steel are related to the carbon content and heat treatment. The carbon content usually ranges from 0.25 to 2 percent. As the percentage of carbon is increased, the tensile strength of the steel also enhances, but the ductility drops. Steel with 2 percent carbon resembles "cast iron" in being hard and brittle. On the other hand, steel containing a small proportion of carbon is soft and ductile like "wrought iron," and is called "mild steel."
The melting point of steel varies from 1,298.89 to 1,500 degree C. If steel is heated to redness and quenched in cold water, it gets very hard and brittle, and the product is known as "quenched steel." If this is again heated in between 200 to 300 degree C and allowed to cool slowly, the steel recovers its elasticity to some extent. This process is known as "tempering." By adjusting the temperature of tempering, steel of any desired degree of hardness can be produced. The surface color of steel changes according to temperature due to the presence of a thin oxide film during tempering. For instance, heating it to 230 degree C produces a pale yellow color, while an intense blue color is formed by heating to 300 degree C.
Special and Alloy Steels. Silicon, titanium, vanadium, molybdenum, chromium, manganese, tungsten, nickel and cobalt are used in the production of special steels with desired physical and mechanical properties. Sometimes, more than one of these elements is used. They are generally added to the melt steel in an electric furnace. For example:
· Silicon steel containing about 3.5 percent silicon and very little carbon is employed for making electromagnets and transformers.
· The presence of 2 percent of chromium in steel makes it very tough, suitable for ball-bearings and armor plates.
· Stainless steel contains about 12 to 15 percent chromium, and is resistant to the action of organic acids.
Application. Steel is extensively employed for structural purposes, for making tools, machineries, railroads and domestic articles. It is also used for making bar magnets, magnetic needles, armor plates, razors, knives, swords, watches and springs.
http://metallics.org.uk/how-iron-and-steel-work/
Vocabulary:
| Substance – вещество To heat- нагревать Shortage – нехватка, недостаток Earth's crust – земная кора ferric oxide – оксид железа (III) melt – плавить ferrous ammonium sulphate solution – раствор сернокислой закиси железа и амония decomposition – разложение, распад iron pentacarbonyl – пентакарбонил железа soft – мягкий melting point – точка (температура) плавления boiling point – точка кипения quenching – закалка allotropic form – аллотропическая модификация to dissolve – растворять To rust- ржаветь moist air – влажный воздух combustion – горение, сжигание Steel – сталь specified ratio – установленное соотношение | manganese – марганец tungsten – вольфрам to impart – передавать heat treatment – термообработка tensile strength – прочность на растяжение to enhance – усиливать, увеличивать cast iron – чугун wrought iron – ковкий чугун mild steel – малоуглеродистая сталь quenched steel – закаленная сталь elasticity - упругость to some extent – до некоторой степени tempering – нормализация oxide film – оксидная пленка Silicon – кремний electric furnace – электрическая печь Tough – вязкий, прочный ball-bearing – шариковый подшипник armor plates – броневая плита Stainless steel – нержавеющая сталь organic acid – органическая кислота |
WORKSHEET 1
A. RESTORE THE INFORMATION ON THE LECTURER’S BLACKBOARD:
| HOW TO MAKE STEEL ____5 – 96% 11_____ C Carbon % ________________ Vanadium _______________ Tungsten ______________elements ___________________ _________________ |
B. Give definitions to the following words:
| Trace element | is that improves |
| Steel | is an alloy |
| Stainless | is steel property |
C. Explain the meaning of the words:
| To improve | |
| To rust |
D. WRITE AN ABSTRACT ABOUT MAKING STEEL
| HOW TO MAKE STEEL |
Individual work:
r ead the text 3 and make the tasks below:
Unit 2
What is welding?
| 1. Basic Level Text 1. The world of welding 2. Basic Level Text 2.WELDING 3. Grammar: Passive Voice, either....or; both....and 4. Text 3. HISTORY OF WELDING 5. Text 4. HISTORY OF WELDING - IN THE BEGINNING |
Basic level:
Text1. The world of welding
The technology of welding has contributed greatly toward making the world better, more productive and a more wonderful place in which to live. Welding is used in the manufacture of almost everything made of metal - ships, locomotive, railroad rails and care, automobiles, pipelines, tanks, aircraft, and household appliances.
Welding used today in so many important industries of our national economy, that if welding disappeared, we might say: «Without welding the world would fall apart». It keeps railroads, truck fleets, steel mills, power plants. Nuclear power plants and spaceships, translators and vacuum tubes, gas-turbine wheels and diaphragms require modern welding technology and quite unusual welding processes.
No present-day technological process has developed at such a rapid race as that of welding. Just a few years ago the ordinary manual arc welding processes was the basic method used in industry. Arc welding, resistance welding, gas welding, shielded inert-gas metal-arc welding, electro-slag welding, atomic hydrogen welding, ultrasonic welding and other commercial processes of manual and automatic welding are widely used in our country.
The scientific and technical aspects of electronic welding are studied by many research establishments, departments of higher schools and factory laboratories. The science and technology of welding have an important part to play in the future world. Without welding interplanetary liners cannot be built, welding is necessary for building launching sites on other planets and in outer space.
Among the means that would be used in the future to join refractory metals and other materials are high frequency current ultrasonic, plasma, controlled fusion and electron beam. The very term «Welding» would become old-fashioned and welding would be replaced by a kind of «gluing» or «cold welding», with which the metal was not heated to melting point but was joined by means of tremendous compression and the uniting of atoms.
Comments:
1. no process - никакой процесс
2. as that of - «that» заменяет существительное
3. in the field - in the field of welding
4. the very term - сам термин
Text 2. Welding
Welding is a fabrication or sculptural process that joins materials, usually metals or thermoplastics, by causing coalescence. This is often done by melting the workpieces and adding a filler material to form a pool of molten material (the weld pool) that cools to become a strong joint, with pressure sometimes used in conjunction with heat, or by itself, to produce the weld. This is in contrast with and brazing, which involve melting a lower-melting-point material between the workpieces to form a bond between them, without melting the workpieces.
Many different energy sources can be used for welding, including a gas , an electric arc, a laser, an electron beam, friction, and ultrasound. While often an industrial process, welding can be done in many different environments, including open air, under water and in outer space. Regardless of location, however, welding remains dangerous, and precautions are taken to avoid burns, electric shock, eye damage, poisonous fumes, and overexposure to ultraviolet light.
Until the end of the 19th century, the only welding process was forge welding, which blacksmiths had used for centuries to join iron and steel by heating and hammering them. Arc welding and oxyfuel welding were among the first processes to develop late in the century, and resistance welding followed soon after. Welding technology advanced quickly during the early 20th century as World War I and World War II drove the demand for reliable and inexpensive joining methods. Following the wars, several modern welding techniques were developed, including manual methods like shielded metal arc welding, now one of the most popular welding methods, as well as semi-automatic and automatic processes such as gas metal arc welding, submerged arc welding, flux-cored arc welding and electroslag welding. Developments continued with the invention of laser beam welding and electron beam welding in the latter half of the century. Today, the science continues to advance. Robot welding is becoming more commonplace in industrial settings, and researchers continue to develop new welding methods and gain greater understanding of weld quality and properties.
Vocabulary:
| fabrication – производство coalescence – соединение, слияние melting – плавление pressure – давление heat – тепло, нагревать brazing –пайка, спайка electron beam- электронный луч friction – трение ultrasound – сверхзвукоковой under water- подводный space – пространство, космос forge welding – кузнечная сварка resistancewelding – контактная сварка shielded metal arc welding– дуговая сварка защищенным электродом energy source - источник тепла | process – процесс elecrtoslsg welding — элекрошлаковая сварка flux-cored arc welding – дуговая сварка под флюсом filler material- присадочный материал bond– связывать quality– качество joint– соединение property– свойство workpiece– деталь thermoplastic– термопластичный submerged arc welding – дуговая сварка с погружением gas metal arc welding – газово-металлическая дуговая сварка |
Text 3. History of welding
The history of joining metals goes back several millennia, with the earliest examples of welding from the Bronze Age and the Iron Age in Europe and the Middle East. Welding was used in the construction of the iron pillar in Delhi, India, erected about 310 AD and weighing 5.4metric tons.
The Middle Ages brought advances in forge welding, in which blacksmiths pounded heated metal repeatedly until bonding occurred. In 1540, Vannoccio Biringuccio published De la pirotechnia, which includes descriptions of the forging operation. Renaissance craftsmen were skilled in the process, and the industry continued to grow during the following centuries. Welding, however, was transformed during the 19th century.
In 1802, Russian scientist Vasily Petrov discovered the electric arc and subsequently proposed its possible practical applications, including welding. In 1881-82 a Russian inventor Nikolai Benardos created the first electric arc welding method known as carbon arc welding, using carbon electrodes. The advances in arc welding continued with the invention of metal electrodes in the late 1800s by a Russian, Nikolai Slavyanov (1888), and an American, C. L. Coffin (1890). Around 1900, A. P. Strohmenger released a coated metal electrode in Britain, which gave a more stable arc. In 1905 Russian scientist Vladimir Mitkevich proposed the usage of three-phase electric arc for welding. In 1919, alternating current welding was invented by C. J. Holslag but did not become popular for another decade.
Resistance welding was also developed during the final decades of the 19th century, with the first patents going to Elihu Thomson in 1885, who produced further advances over the next 15 years. Thermite welding was invented in 1893, and around that time another process, oxyfuel welding, became well established. Acetylene was discovered in 1836 by Edmund Davy, but its use was not practical in welding until about 1900, when a suitable blowtorch was developed at first, oxyfuel welding was one of the more popular welding methods due to its portability and relatively low cost. As the 20th century progressed, however, it fell out of favor for industrial applications. It was largely replaced with arc welding, as metal coverings (known as flux) for the electrode that stabilize the arc and shield the base material from impurities continued to be developed.
World War I caused a major surge in the use of welding processes, with the various military powers attempting to determine which of the several new welding processes would be best. The British primarily used arc welding, even constructing a ship, the Fulagar, with an entirely welded hull. Arc welding was first applied to aircraft during the war as well, as some German airplane fuselages were constructed using the process.Also noteworthy is the first welded road bridge in the world, designed by Stefan Bryła of the Warsaw University of Technology in 1927, and built across the river Słudwia Maurzyce near Łowicz, Poland in 1929.
During the 1920s, major advances were made in welding technology, including the introduction of automatic welding in 1920, in which electrode wire was fed continuously. Shielding gas became a subject receiving much attention, as scientists attempted to protect welds from the effects of oxygen and nitrogen in the atmosphere. Porosity and brittleness were the primary problems, and the solutions that developed included the use of hydrogen, argon, and helium as welding atmospheres. During the following decade, further advances allowed for the welding of reactive metals like aluminum and magnesium. This in conjunction with developments in automatic welding, alternating current, and fluxes fed a major expansion of arc welding during the 1930s and then during World War II.
During the middle of the century, many new welding methods were invented. 1930 saw the release of stud welding, which soon became popular in shipbuilding and construction. Submerged arc welding was invented the same year and continues to be popular today. In 1932 a Russian, Konstantin Khrenov successfully implemented the first underwater electric arc welding. Gas tungsten arc welding, after decades of development, was finally perfected in 1941, and gas metal arc welding followed in 1948, allowing for fast welding of non-ferrous materials but requiring expensive shielding gases. Shielded metal arc welding was developed during the 1950s, using a flux-coated consumable electrode, and it quickly became the most popular metal arc welding process. In 1957, the flux-cored arc welding process debuted, in which the self-shielded wire electrode could be used with automatic equipment, resulting in greatly increased welding speeds, and that same year, plasma arc welding was invented. Electroslag welding was introduced in 1958, and it was followed by its cousin, electrogas welding, in 1961. In 1953 the Soviet scientist N. F. Kazakov proposed the diffusion bonding method.
Other recent developments in welding include the 1958 breakthrough of electron beam welding, making deep and narrow welding possible through the concentrated heat source. Following the invention of the laser in 1960, laser beam welding debuted several decades later, and has proved to be especially useful in high-speed, automated welding. In 1991 friction stir welding was invented in the UK and found high-quality applications all over the world. All of these three new processes, however, continue to be quite expensive due the high cost of the necessary equipment, and this has limited their applications.
VOCABULARY:
| application - применение carbon electrode - угольный электрод arc welding - дуговая сварка invention - изобретение coated metal electrode - покрытый металлом электрод scientist - ученый alternating current - переменный тoк | attempt - попытка torch - горелка determine - определять porosity - пористость brittleness - хрупкость heat source - источник энергии stud welding - сварка встык |
ИСТОРИЯ РАЗВИТИЯ СВАРКИ
Основоположниками использования тепла электрической дуги для целей сварки были русские ученые В. В. Петров, Н. Н. Бенардос и Н. Г. Славянов.
В 1802 г. впервые в мире профессор физики Санкт-Петербургской Медико-хирургической академии Василий Владимирович Петров открыл электрическую дугу. Русский изобретатель Николай Николаевич Бенардос в 1882 г впервые применил электрическую дугу для соединения в одно целое металлов, использовав угольную дугу, питаемую электрической энергией от аккумуляторной батареи. В 1885 г. он получил патент под названием «Способ соединения и разъединения металлов непосредственным действием электрического тока». Н. И. Бенардос является автором и ряда других видов сварки, которые применяют сейчас в промышленности. Несколько лет спустя, в 1888 г. русский инженер-металлург и изобретатель Н. Г. Славянов разработал вид сварки металлическим электродом и получил два патента.
Exercise 7. Give English equivalents to:
защитный газ, переменный ток, пористость, хрупкость, сварка встык, Электронно-лучевая сварка, дуговая сварка, покрытый металлом электрод, покрытие, электрошлаковая сварка, плазменная сварка, электрический удар, алюминий, магний, углерод, источник тепла
Exercise 8. Find equivalents:
either....or; both....and; not only....but also...; as a rule; such as...; therefore; since
Unit 3
Basic Types of Welding.
| 1. Basic level. Text 1. Forge welding (Part 1) 2. Grammar: Word-building 3. Basic Level. Text 2. Forge welding (Part 2) 4. Higher Level. Text 3. ARC-welding (1) 5. Individual work. Text 4. ARC-welding (2) 6. video: MIG Welding, How to become an electric arc welder |
Basic Level:
Fuel and Furnaces Required
Coal, coke, charcoal, gas and oil can be used in furnaces required to heat objects to the plastic state. Heating must be uniform and neither too much nor too little. Too much heat may burn the metal and produce a brittle weld. Too little heat will prevent the metal from being plastic and thus result, in a weak inadequate weld.
Surface Preparation
Surfaces of the metal pieces to be forge welded are prepared by upsetting the pieces at the ends. Various edge preparations required to be carried out before forge welding.
Procedure for Forge Welding
The parts to be forge welded are given an edge (or joint) preparation as explained above. Then, the parts are heated to over l000°C until they are plastic. In this condition, the parts are placed on the anvil end to end and are hammered together, either using a power hammer or manually, until they form a solid structure of metal.
In forge welding operation, a very important requirement is that during heating the absorption of sulphur from the coke of the fire and scaling of the pieces (to be welded) should be prevented or that if scale is formed, the hammering should be done in such a way as to squeeze this out of the joint and permit metal to metal contact. Besides being united by blows from a hammer, the workpieces may also be welded by being rolled, drawn or squeezed together.
Advantages and Disadvantages and Applications of Forge Welding - If made correctly, a forge welded joint has every quality of the original metal and is as good in strength as an arc or oxyacetylene welded joint.
Disadvantages
(i) Forge welding requires considerable skill on the part of the operator.
(ii) It is restricted to wrought iron and mild steel.
(iii) It is usually limited to the joining together of pieces of solid steel stock.
(vi) It is a slow process as compared to arc and gas welding.
(v) There is the danger of sulphur pickup by the metal from the coke of the furnace.
Applications
(i) Forge welding finds use in blacksmith shops, rail road shops and repair shops of general character.
(ii) (ii) It is also used for making pipes from plates by rolling the plate to cylindrical form and making the longitudinal junction by forge welding. Strip/plate is pulled through dies to form a rolled cylinder, the long edges being butted together in the dies at the high temperature required to form a forge weld
(iii) Types of Forge Welding – 1. Fire welding in which pieces to be joined are heated in the fire by the blacksmith. He withdraws them at the appropriate time and joins them by hammer blows. 2. Water gas welding which finds application in the manufacture of pipes, containers, etc. Edges of the plate (to be converted into a pipe) are heated by water gas flame. (consisting essentially of hydrogen, carbon monoxide and nitrogen) and as they attain the appropriate temperature, they are welded together under the hammer or by means of pressure rollers.
Flux Requirements The flux
(i) gives protection (to metal pieces) from oxidation.
(ii) combines with the oxides to form a fluid slag which is readily squeezed out of the joint thereby preventing the scale from being trapped at any point between the joint surfaces. This produces a sound weld.
(iii) used to dissolve oxides, forms a protective coating and shield over the heated area of the metal and prevents further oxidation and burning of metal. Borax in combination with salammoniac is the most commonly used flux for forge welding steel.
VOCABULARY:
| Coal - уголь weld - шов edge - край, кромка anvil - наковальня considerable - значительный | Shop - цех roll - прокатывать draw - тянуть, вытягивать advantage - преимущество manufacture - производство |
Text3. ARC-welding (1)
Technique of arc welding.
Metal-arc welding is a process of joining two pieces of metal by heating, melting and fusing the edges or surfaces under the temperature of 5,400-6,0000 F. In arc welding, the intense heat, required to reduce metal to a liquid state, is created by an electric arc. The arc is formed between the work to be welded and a metal wire called an electrode. The electrode, held in a suitable holder, is brought close to metal to be welded, forming an arc between the tip of the electrode and the work.
The arc is a means for transforming electrical energy into heat. The tremendous heat, highly concentrated at the tip of the electrode, molten a small pool of metal. The pieces to be joined thus become liquid and fuse together in this molten pool called the crater. At the same time, the end of the electrode at the arc metals, and this molten metal is carried over by the arc to the molten pool on work piece. With a consumable electrode, once the arc is obtained, it is necessary to move the electrode uniformly toward the work piece, thus compensating for the loss of metal at its end. As the areas solidify, the metals are joined into one solid, homogeneous piece. Metal-arc welding is a normally a manual rather than mechanized operation. If the pieces to be joined are relatively thick, it may be necessary to make two or more passes in order to complete the weld.
The arc welding process requires a continuous supply of electric current, sufficient in amount (amperes) and of proper voltage to maintain an arc. This current may be either alternating (AC) or direct (DC). The source of energy must provide a range of voltage across the arc from 17, which in the minimum for starting an arc, to approximately 45 volts. Welding current may vary from 10 amperes to as high as 1,500 and over for automatic welding.
If DC is used, the polarity of the welding circuit is important to correct procedure. DC welding machines have positive and negative terminals. When the electrode is connected to the negative terminal, «straight» or standard polarity is used. This means that the current is flowing from the work to the electrode. By changing the lead or polarity switch the current will flow in the opposite direction, from electrode to work. This is known as «reveres» polarity. Most welding machines are equipped with a polarity switch for reversing the flow of current without changing the lead cables at the terminals.
Several different types of welding machines are available for satisfactory welding current. Direct current. Direct current is produced in either electric motorgenerator sets or engine-driven generator sets. Practically all AC arc-welding machines are transformers which take current from an outside source and convert into welding current. Combination welders, producing both AC and DC current, are the most versatile of all types of welders. They are basically a transformer and rectifier with means provided for tapping into the either AC or DC output.
Exercise 12. Answer the questions:
1) What was welding in its original meaning?
2) When does the history of electric arc-welding begin?
3) What did Petrov and Davy investigate?
4)Who was a founder of metal-arc welding?
5) When did he develop metal-arc welding?
6) What is metal-arc welding?
7) How is the welding heat created?
8) Describe briefly the metal-arc welding process?
9) What current is used in the metal-arc?
10) What factors are required for maintaining the arc?
11) How do the voltage and amperes of the welding current used?
12) What machines is direct current produced in?
13) What does «straight polarity» mean?
14) How is «reverse» polarity obtained?
15) What is the A.-C. arc-welding machine?
16) What welding machines are the most versatile types of machines?
17) What metal-arc equipment is there in your laboratory?
18) Did you work as a welding operator?
Exercise 13 . Watch the video HOW TO BECOME AN ELECTRIC ARC WELDER www.youtube.com/watch?v=WaDsmeB5ywM and discuss the following questions:
1. What are the tools for arc welding?
2. How to assemble the welding tool?
3. What is “alive wire”?
4. How to create an electric arc?
5. What happens to a wire when the electric arc is created?
6. What is flux? What is it used for?
7. Tell about the first exercises of an electric arc welder?
8. What is the “rows of neat little dots”?
Exercise 14 . Fill in the Worksheet 3.
| A. TO CLAMP MEANS | · TO FIX · TO PLACE · TO MAKE |
| B. ELECRICALLY CHARGED ELECTRODE IS | ___________________________________ |
| C. TO CREATE AN ELECTRIC ARC YOU NEED AND ELECTRIC ARC | · ____________________ DOWN A PIECE OF STEEL WITH AN ________________ · BEGINS TO _____________________ WIRE. |
| D. WIRE IS COVERED WITH | _____________________________ THAT PREVENTS ______________ AND NITROGEN TO GET IN THE ___________________ . AND __________________ THE WELD FROM THE ATMOSPHERE. |
Individual Work:
Text 4. Arc welding (2).
Arc welding. In arc welding, the heat required to metal the parts being joined is obtained by striking an arc between an electrode and these parts. Both direct and alternating currents are used but direct current is the common. Two kinds of electrode are used: (a) carbon, and (b) metal, and the latter may be (1) bare, (2) coated, or (3) cored. The metal electrode is by far the most widely used, the carbon arc process being now chiefly confined to certain automatic welding machines and for welds that require no filler metal. In direct current welding the electrode is usually made the negative pole and the work positive, because with a carbon electrode the electrode consumption is less and with a metal electrode the heat developed at the anode (the positive pole) is greater than at the cathode (the negative pole). The choice of polarity, however, depends on many factors most coated electrodes weld better when connected to the positive pole rods containing more than about 0,9 per cent of manganese also generally behave better when the rod is made positive. Reversed polarity (rod positive) is also best for aluminum because it gives better control of the penetration on account of the lower temperature of the plate. The voltage applied across the arc ranges from 18 to 30 with metal electrodes and from 80 to 100 with carbon electrodes: it varies with length of arc, and the current and the rate of deposition will vary accordingly. Some of the acquired skill of a good operator is directed to maintaining the arc length constant. The current employed from 20 to 900 amperes with hand-operated arcs but may be as high as 15.000 amperes in automatic welding machines. With metal electrodes the rate of deposition is roughly proportional to the current employed. Metal electrodes vary between 1/16 and 3/8 in. diameter and are usually from 12 to 18 in. long. The reminder of this section is restricted to metal arc welding.
The current used must be related to the size of electrode and the nature of the work being done. Too low a current is likely to result in poor penetration, the electrode being melted and merely dropped on the job, which is not properly fused. Too high a current results in overheating of the electrode and a poor weld; it also causes excessive spattering and waste of electrode. Nevertheless it is better to use too high than too low a current. With coated electrodes too high a current tends to prevent the slag from covering and protecting the weld deposit, while too low a current produces a viscous slag and increases the risk of slag inclusions in the weld metal. Some idea of the currents used is given by the following table:
| Gauge of electrode | Current, amps |
| 12 | 80-110 |
| 10 | 110-140 |
| 8 | 130-170 |
| 6 | 160-240 |
| 4 | 180-280 |
Unit 4
Basic Level
Fusion welding.
The field of fusion welding can be broken into several processes, the most important of which are arc welding, electroslag welding, gas-shielded arc welding, gas welding, electron beam welding, and plasma-jet welding.
In all arc processes, the source of heat is an electric arc whose temperature may be as high as 6000K (5727 C).
Manual Metal-arc Welding (the Slavianoff process) (Fig.5). In this process an arc 1 is established between the work to be welded 2 and a metallic wire, or electrode 4, clamped in an electrode-holder 5. The intense heat of the arc melts some of the parent metal and tip of the electrode. The molten metal fills the groove between the edges of the work and, on cooling, forms a weld 3.
Exercise 1. Match the words:
| Melting temperature | край, кромка |
| Parent metal | обрабатываемое изделие |
| Filler metal | проволока |
| Flux | температура плавления |
| Edge | присадочный металл |
| Weld pool | основной металл |
| The work | ручная дуговая сварка мет. эл. |
| Wire | флюс |
| Gas shielded arc w. | газоэлектрическая сварка |
| Manual metal arc w. | сварочная ванна |
Exercise 2. Translate the following groups of words:
fusion
pressure
arc
gas
gas shielded arc
manual metal arc welding
electron beam
plasma-jet
low
high temperature
melting
welding
filler
weld metal
parent
высокая
низкая
температура плавления
сварки
высокого качества
шов
низкого качества
Exercise 3. Translate the following nouns with preposition:
example: to melt – плавить; melting –плавление
| 1. to weld - welding 2. to join – joining 3. to heat – heating 4. to coat - coating | 5. to cool – cooling 6. to melt – melting 7. to bond – bonding 8. to cover - covering |
Exercise 4. Fill gaps with prepositions: owing to, between, by, to, on, below, around
1. Joining takes place … the formation of bonds … atoms.
2. Two pieces of metal are joined … heating … a melting temperature.
3. A weld is formed … cooling.
4. In pressure welding the works are heated … a temperature … melting-point.
5. A weld is formed … applying pressure.
6. There is a covering … the weld pool.
7. An arc is established … the work and a metallic were.
Text 4. Spot welding
Spot welding . Spot welding is a resistance welding method used to join two to four overlapping metal sheets which are up to 3 mm thick each. In some applications with only two overlapping metal sheets, the sheet thickness can be up to 6 mm. Two copper electrodes are simultaneously used to clamp the metal sheets together and to pass current through the sheets. When the current is passed through the electrodes to the sheets, heat is generated due to the higher electrical resistance where the surfaces contact each other. As the heat dissipates into the work, the rising temperature causes a rising resistance, and the heat is then generated by the current through this resistance. The surface resistance lowers quickly, and the heat is soon generated only by the materials' resistance. The water cooled copper electrodes remove the surface heat quickly, since copper is an excellent conductor. The heat in the center has nowhere to go, as the metal of the workpiece is a poor conductor of heat by comparison. The heat remains in the center, melting the metal from the center outward. As the heat dissipates throughout the workpiece in less than a second the molten, or at least plastic, state grows to meet the welding tips. When the current is stopped the copper tips cool the spot weld, causing the metal to solidify under pressure. Some coatings, such as zinc, cause localized heating due to its high resistance, and may require pulsation welding to dissipate the unwanted surface heat into the copper tips.
If excessive heat is applied, or applied too quickly, the molten area may extend to the outside, and with its high pressure (typically 30,000 psi) will escape the containment force of the tips with a burst of molten metal called expulsion. When this occurs, the metal will be thinner and have less strength than a weld with no expulsion. The common method of checking a weld is a peel test, technically called "coach peel", as expulsion weakens the material by thinning, and makes it pass the peel test easier. A better test is the tensile test, which is much more difficult to perform, and requires calibrated equipment.
The advantages of the method include efficient energy use, limited workpiece deformation, high production rates, easy automation, and no required filler materials. When high strength in shear is needed, spot welding is used in preference to more costly mechanical fastening, such as riveting. While the shear strength of each weld is high, the fact that the weld spots do not form a continuous seam means that the overall strength is often significantly lower than with other welding methods, limiting the usefulness of the process. It is used extensively in the automotive industry— cars can have several thousand spot welds. A specialized process, called shot welding, can be used to spot weld stainless steel.
There are three basic types of resistance welding bonds: solid state, fusion, and reflow braze. In a solid state bond, also called a thermo-compression bond, dissimilar materials with dissimilar grain structure, e.g. molybdenum to tungsten, are joined using a very short heating time, high weld energy, and high force. There is little melting and minimum grain growth, but a definite bond and grain interface. Thus the materials actually bond while still in the “solid state”. The bonded materials typically exhibit excellent shear and tensile strength, but poor peel strength. In a fusion bond, either similar or dissimilar materials with similar grain structures are heated to the melting point (liquid state) of both. The subsequent cooling and combination of the materials forms a “nugget” alloy of the two materials with larger grain growth. Typically, high weld energies at either short or long weld times, depending on physical characteristics, are used to produce fusion bonds. The bonded materials usually exhibit excellent tensile, peel and shear strengths. In a reflow braze bond, a resistance heating of a low temperature brazing material, such as gold or solder, is used to join either dissimilar materials or widely varied thick/thin material combinations. The brazing material must “wet” to each part and possess a lower melting point than the two workpieces. The resultant bond has definite interfaces with minimum grain growth. Typically the process requires a longer (2 to 100 ms) heating time at low weld energy. The resultant bond exhibits excellent tensile strength, but poor peel and shear strength.
Vocabulary:
| Spot welding - точечная сварка copper electrode - медный электрод conductor - проводник riveting - соединять заклепками | Fusion - сплав subsequent - последовательный grain - зерно alloy - сплав |
What is spot welding?
Text 5.Seam welding
Resistance seam welding is a process that produces a weld at the faying surfaces of two similar metals. The seam may be a butt joint or an overlap joint and is usually an automated process. It differs from butt welding in that butt welding typically welds the entire joint at once and seam welding forms the weld progressively, starting at one end. Like spot welding, seam welding relies on two electrodes, usually made from copper, to apply pressure and current. The electrodes are disc shaped and rotate as the material passes between them. This allows the electrodes to stay in constant contact with the material to make long continuous welds. The electrodes may also move or assist the movement of the material.
A transformer supplies energy to the weld joint in the form of low voltage, high current AC power. The joint of the work piece has high electrical resistance relative to the rest of the circuit and is heated to its melting point by the current. The semi-molten surfaces are pressed together by the welding pressure that creates a fusion bond, resulting in a uniformly welded structure. Most seam welders use water cooling through the electrode, transformer and controller assemblies due to the heat generated. Seam welding produces an extremely durable weld because the joint is forged due to the heat and pressure applied. A properly welded joint formed by resistance welding is typically stronger than the material from which it is formed.
A common use of seam welding is during the manufacture of round or rectangular steel tubing. Seam welding has been used to manufacture steel beverage cans but is no longer used for this as modern beverage cans are seamless aluminum.
Vocabulary :
Faying surfaces - плотно соединенные поверхности
Voltage - напряжение
round - круглый
rectangular - прямоугольный
modern - современный
SUPPLEMENTARY TEXTS
Text A.
«WELDING»
Welding is a process when metal parts are joined together by the application of heat, pressure, or a combination of both. The processes of welding can be divided into two main groups:
• pressure welding, when the weld is achieved by pressure and
• heat welding, when the weld is achieved by heat. Heat welding is the most common welding process used today.
Nowadays welding is used instead of bolting and riveting in the construction of many types of structures, including bridges, buildings, and ships. It is also a basic process in the manufacture of machinery and in the motor and aircraft industries. It is necessary almost in all productions where metals are used.
The welding process depends greatly on the properties of the metals, the purpose of their application and the available equipment. Welding processes are classified according to the sources of heat and pressure used.
The welding processes widely employed today include gas welding, arc welding, and resistance welding. Other joining processes are laser welding, and electron-beam welding.
Gas Welding
Gas welding is a non-pressure process using heat from a gas flame. The flame is applied directly to the metal edges to be joined and simultaneously to a filler metal in the form of wire or rod, called the welding rod, which is melted to the joint. Gas welding has the advantage of using equipment that is portable and does not require an electric power source. The surfaces to be welded and the welding rod are coated with flux, a fusible material that shields the material from air, which would result in a defective weld.
Arc Welding
Arc-welding is the most important welding process for joining steels. It requires a continuous supply of either direct or alternating electrical current. This current is used to create an electric arc, which generates enough heat to melt metal and create a weld.
Arc welding has several advantages over other welding methods. Arc welding is faster because the concentration of heat is high. Also, fluxes are not necessary in certain methods of arc welding. The most widely used arc-welding processes are shielded metal arc, gas-tungsten arc, gas-metal arc, and submerged arc.
Shielded Metal Arc
In shielded metal-arc welding, a metallic electrode, which conducts electricity, is coated with flux and connected to a source of electric current. The metal to be welded is connected to the other end of the same source of current. An electric arc is formed by touching the tip of the electrode to the metal and then drawing it away. The intense heat of the arc melts both parts to be welded and the point of the metal electrode, which supplies filler metal for the weld. This process is used mainly for welding steels.
Английский язык для технических ВУЗов. Агабекян И.П., Коваленко П.И. Ростов-на-Дону: Феникс, 2008. - 302 с
Gas-Metal Arc
In gas-metal welding, a bare electrode is shielded from the air by surrounding it with argon or carbon dioxide gas and sometimes by coating the electrode with flux. The electrode is fed into the electric arc, and melts off in droplets that enter the liquid metal of the weld seam. Most metals can be joined by this process.
Submerged Arc
Submerged-arc welding is similar to gas-metal arc welding, but in this process no gas is used to shield the weld. Instead of that, the arc and tip of the wire are submerged beneath a layer of granular, fusible material that covers the weld seam. This process is also called electroslag welding. It is very efficient but can be used only with steels.
Resistance Welding
In resistance welding, heat is obtained from the resistance of metal to the flow of an electric current. Electrodes are clamped on each side of the parts to be welded, the parts are subjected to great pressure, and a heavy current is applied for a short period of time. The point where the two metals touch creates resistance to the flow of current. This resistance causes heat, which melts the metals and creates the weld. Resistance welding is widely employed in many fields of sheet metal or wire manufacturing and is often used for welds made by automatic or semi-automatic machines especially in automobile industry.
Английский язык для технических ВУЗов. Агабекян И.П., Коваленко П.И. Ростов-на-Дону: Феникс, 2008. - 302 с
Text C
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. Therefore, the electrode, if consumable, is made positive and, if non-consumable, is made negative. A direct current (dc) arc is usually used, but alternating current (ac) arcs can be employed.
Total energy input in all welding processes exceeds that which is required to produce a joint, because not all the heat generated can be effectively utilized. Efficiencies vary from 60 to 90 percent, depending on the process; some special processes deviate widely from this figure. Heat is lost by conduction through the base metal and by radiation to the surroundings.
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 oxidize 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 a 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.
The metallurgy of metal joining is important to the functional capabilities of the joint. The arc weld illustrates all the basic features of a joint. Three zones result from the passage of a welding arc: (1) the weld metal, or fusion zone, (2) the heat-affected zone, and (3) the unaffected zone. The weld metal is that portion of the joint that has been melted during welding. The heat-affected zone is a region adjacent to the weld metal that has not been welded but has undergone a change in microstructure or mechanical properties due to the heat of welding. The unaffected material is that which was not heated sufficiently to alter its properties.
Weld-metal composition and the conditions under which it freezes (solidifies) significantly affect the ability of the joint to meet service requirements. In arc welding, the weld metal comprises filler material plus the base metal that has melted. After the arc passes, rapid cooling of the weld metal occurs. A one-pass weld has a cast structure with columnar grains extending from the edge of the molten pool to the center of the weld. In a multipass weld, this cast structure maybe modified, depending on the particular metal that is being welded.
The base metal adjacent to the weld, or the heat-affected zone, is subjected to a range of temperature cycles, and its change in structure is directly related to the peak temperature at any given point, the time of exposure, and the cooling rates. The types of base metal are too numerous to discuss here, but they can be grouped in three classes: (1) materials unaffected by welding heat, (2) materials hardened by structural change, (3) materials hardened by precipitation processes.
Welding produces stresses in materials. These forces are induced by contraction of the weld metal and by expansion and then contraction of the heat-affected zone. The unheated metal imposes a restraint on the above, and as contraction predominates, the weld metal cannot contract freely, and a stress is built up in the joint. This is generally known as residual stress, and for some critical applications must be removed by heat treatment of the whole fabrication. Residual stress is unavoidable in all welded structures, and if it is not controlled bowing or distortion of the weldment will take place.
Arc welding
Shielded metal-arc welding accounts for the largest total volume of welding today. In this process an electric arc is struck between the metallic electrode and the workpiece. Tiny globules of molten metal are transferred from the metal electrode to the weld joint. Arc welding can be done with either alternating or direct current. A holder or clamping device with an insulated handle is used to conduct the welding current to the electrode. A return circuit to the power source is made by means of a clamp to the workpiece.
Gas-shielded arc welding, in which the arc is shielded from the air by an inert gas such as argon or helium, has become increasingly important because it can deposit more material at a higher efficiency and can be readily automated. The tungsten electrode version finds its major applications in highly alloyed sheet materials. Either direct or alternating current is used, and filler metal is added either hot or cold into the arc. Consumable electrode gas-metal arc welding with a carbon dioxide shielding gas is widely used for steel welding. Metal transfer is rapid, and the gas protection ensures a tough weld.
Submerged arc welding is similar to the above except that the gas shield is replaced with a granulated mineral material as a flux.
Weldability of metals
Carbon and low-alloy steels are the most widely used materials in welded construction. Carbon content largely determines the weldability of carbon steels. Low-alloy steels are generally regarded as those having a total alloying content of less than 6 percent. There are many grades of steel available, and their relative weldability varies.
Aluminum and its alloys are also generally weldable. A very thin oxide film on aluminum tends to prevent good metal flow, however, and suitable fluxes are used for gas welding. Fusion welding is more effective with alternating current when using the gas-tungsten arc process to enable the oxide to be removed by the arc action.
Copper and its alloys are weldable, but the high thermal conductivity of copper makes welding difficult. Metals such as zirconium, niobium, molybdenum, tantalum, and tungsten are usually welded by the gas-tungsten arc process. Nickel is the most compatible material for joining, is weldable to itself, and is extensively used in dissimilar metal welding of steels, stainless steels and copper alloys.
Английский язык для технических ВУЗов. Агабекян И.П., Коваленко П.И. Ростов-на-Дону: Феникс, 2008. - 302 с
Text D
DIRECT-CURRENT (DC) GENERATORS
If an armature revolves between two stationary field poles, the current in the armature moves in one direction during half of each revolution and in the other direction during the other half. To produce a steady flow of unidirectional, or direct, current from such a device, it is necessary to provide a means of reversing the current flow outside the generator once during each revolution. In older machines, this reversal is accomplished by means of a commutator (коллектор) — a split metal ring mounted on the shaft of the armature. The two halves of the ring are insulated from each other and serve as the terminals of the armature coil. Fixed brushes of metal or carbon are held against the commutator as it revolves, connecting the coil electrically to external wires. As the armature turns, each brush is in contact alternately with the halves of the commutator, changing position at the moment when the current in the armature coil reverses its direction. Thus, there is a flow of unidirectional current in the outside circuit to which the generator is connected. DC generators are usually operated at fairly low voltages to avoid the sparking between brushes and commutator that occurs at high voltage. The highest potential commonly developed by such generators is 1500 V. In some newer machines this reversal is accomplished using power electronic devices, for example, diode rectifiers.
Modern DC generators use drum armatures that usually consist of a large number of windings set in longitudinal slits in the armature core and connected to appropriate segments of a multiple commutator. In an armature having only one loop of wire, the current produced will rise and fall depending on the part of the magnetic field through which the loop is moving. A commutator of many segments used with a drum armature always connects the external circuit to one loop of wire moving through the high-intensity area of the field, and as a result the current delivered by the armature windings is virtually constant. Fields of modern generators are usually equipped with four or more electromagnetic poles to increase the size and strength of the magnetic field. Sometimes smaller interpoles are added to compensate for distortions in the magnetic flux of the field caused by the magnetic effect of the armature.
DC generators are commonly classified according to the method used to provide field current for energizing the field magnets. A series-wound generator has its field in series with the armature, and a shunt-wound generator has the field connected in parallel with the armature. Compound-wound generators have part of their fields in series and part in parallel. Both shunt-wound and compound-wound generators have the advantage of delivering comparatively constant voltage under varying electrical loads. The series-wound generator is used principally to supply a constant current at variable voltage. A magneto is a small DC generator with a permanent-magnet field
Английский язык для технических ВУЗов. Агабекян И.П., Коваленко П.И. Ростов-на-Дону: Феникс, 2008. - 302 с
Text E
AC MOTORS
Two basic types of motors are designed to operate on alternating current: synchronous motors and induction motors. The synchronous motor is essentially a three-phase alternator operated in reverse. The field magnets are mounted on the rotor and are excited by direct current, and the armature winding is divided into three parts and fed with three-phase alternating current. The variation of the three waves of current in the armature causes a varying magnetic reaction with the poles of the field magnets, and makes the field rotate at a constant speed that is determined by the frequency of the current in the AC power line.
The constant speed of a synchronous motor is advantageous in certain devices. However, in applications where the mechanical load on the motor becomes very great, synchronous motors cannot be used, because if the motor slows down under load it will «fall out of step» with the frequency of the current and come to a stop. Synchronous motors can be made to operate from a single-phase power source by the inclusion of suitable circuit elements that cause a rotating magnetic field.
The simplest of all electric motors is the squirrel-cage type of induction motor used with a three-phase supply. The armature of the squirrel-cage motor consists of three fixed coils similar to the armature of the synchronous motor. The rotating member consists of a core in which are imbedded a series of heavy conductors arranged in a circle around the shaft and parallel to it. With the core removed, the rotor conductors resemble in form the cylindrical cages once used to exercise pet squirrels. The three-phase current flowing in the stationary armature windings generates a rotating magnetic field, and this field induces a current in the conductors of the cage. The magnetic reaction between the rotating field and the current-carrying conductors of the rotor makes the rotor turn. If the rotor is revolving at exactly the same speed as the magnetic field no currents will be induced in it, and hence the rotor should not turn at a synchronous speed. In operation the speeds of rotation of the rotor and the field differ by about 2 to 5 per cent. This speed difference is known as slip.
Motors with squirrel-cage rotors can be used on single-phase alternating current by means of various arrangements of inductance and capacitance that alter the characteristics of the single-phase voltage and make it resemble a two-phase voltage. Such motors are called split-phase motors or condenser motors (or capacitor motors), depending on the arrangement used. Single-phase squirrel-cage motors do not have a large starting torque, and for applications where such torque is required, repulsion-induction motors are used. A repulsion-induction motor may be of the split-phase or condenser type, but has a manual or automatic switch that allows current to flow between brushes on the commutator when the motor is starting, and short-circuits all commutator segments after the motor reaches a critical speed. Repulsion-induction motors are so named because their starting torque depends on the repulsion between the rotor and the stator, and their torque while running depends on induction. Series-wound motors with commutators, which will operate on direct or alternating current, are called universal motors. They are usually made only in small sizes and are commonly used in household appliances.
Английский язык для технических ВУЗов. Агабекян И.П., Коваленко П.И. Ростов-на-Дону: Феникс, 2008. - 302 с
Text F
Список литературы
Основная литература:
1. Булдакова Р.П., Колупаева Н.М. Методические рекомендации по чтению профессионально-ориентированных текстов для студентов, магистрантов и аспирантов. – Ижевск, 2012. (Рег. № 1415/880 CD).
2. Корепанова О.П. Методические рекомендации для студентов неязыковых направлений по развитию навыков и умений научно-технического перевода . – Ижевск: ИжГТУ, 2012. (Рег. № 1378/857 CD)
3 Кочурова М.М., Волкова Д.А. Учебно-методические рекомендации для студентов по развитию умений иноязычной письменной речи. Ижевск: ИжГТУ, 2013. (Рег.№ 02/13 ФГОС)
Дополнительная литература:
1. Английский язык для технических ВУЗов. Агабекян И.П., Коваленко П.И. Ростов-на-Дону: Феникс, 2008. - 302 с
2. Т.И.Алантьева, О.Э.Боярчук, О.В.Гилёва. Мир физики. Пособие по английскому языку для студентов инженерно-технических специальностей. Гродно, ГрГУ им. Я.Купалы. 2008. http://ebooks.grsu.by/physics_world/unit-1.htm
3. И.В. Орловская, Л.С. Самсонова, А.И. Скубриева. Учебник английского языка для технических университетов и вузов.Москва. Изд-во МГТУ им. Н.Э. Баумана. 2006.
4. В.П. Смекаев. Учебник технического перевода. Английский язык. Нижний Новгород. 2006.
5. Чернявская Л.Ф. Английский язык. Теплотехника: Учебное пособие. Братск: Федеральное агентство по образованию ГОУ ВПО «Братский государственный университет», 2009. 71 с.
6. Луговая А. Л. Английский язык для студентов энергетических специальностей. М.: Высшая школа, 2009. 152 с.
7. Сидоренко Ю.Н. Теплоэнергетика: методические указания по английскому языку. Омск: Издательство ОмГТУ, 2010.
8. Федорова Н.Т., Архипова Е.И., и др. Electrical Engineering. Ижевск, 2010. 72 с.
УДК 802.0 (075)
ББК 81.4 Англ – 92
Ф53
Р е ц е н з е н т: Архипова Е.И., канд. пед. наук, доцент, зав. кафедрой «Английский язык» ФГБОУ ВО «ИжГТУ им. М.Т. Калашникова»
Составители: Волкова Д.А., старший преподаватель;
Филинова Е.Ф., ассистент
Учебное пособие по английскому языку для студентов второго курса очного и заочного отделений направления 15.03.01 Машиностроение, профиль: «Оборудование и технология сварочного производства» / сост. Д. А. Волкова, Е. Ф. Филинова. – Ижевск: Изд-во ИжГТУ, 2016 . – 64с.
УДК 802.0 (075)
ББК 81.4 Англ – 92
Ф53
Учебное пособие предназначено для студентов 2 курса очного и заочного отделений, обучающихся по направлению 15.03.01 Машиностроение, профиль: «Оборудование и технология сварочного производства». Может быть рекомендовано для магистрантов и аспирантов при самостоятельном изучении английского языка.
В пособие включены аутентичные тексты профессиональной направленности по соответствующим вышеуказанным профилям, комплекс речевых упражнений. Предтекстовые задания ориентированы на введение ключевых слов и словосочетаний, терминов путем выполнения задания на нахождение соответствий между английским словом и его значением на русском языке. Послетектовые упражнения направлены на развитие умений поиска специальной информации по прочитанному тексту. Применение ИКТ (видео, интернет-ресурсы) в данном учебном пособии способствует более эффективному изучению предметной области на иностранном языке.
© Д. А. Волкова, Е.Ф. Филинова, 2016
© Издательство ИжГТУ, 2016
Введение
Учебное пособие предназначено для студентов 2 курса очного и заочного отделений, обучающихся по направлению 15.03.01 Машиностроение, профиль: «Оборудование и технология сварочного производства».
Пособие состоит из введения, 4 тематических блоков, включающих в себя темы соответствующие уровням подготовки студентов (основной, повышенный), видеоматериалов, заданий для самостоятельной работы студентов.
Каждый блок содержит аутентичный текстовый материал профессиональной направленности, соответствующий вышеуказанным профилям, комплекс речевых упражнений.
Представлены предтекстовые и послетекстовые упражнения. Предтекстовые задания ориентированы на введение ключевых слов и словосочетаний, терминов путем выполнения задания на нахождение соответствий между английским словом и его значением на русском языке.
Послетектовые упражнения направлены на развитие умений поиска специальной информации по прочитанному тексту и предусматривают выполнение заданий на заполнение пропусков в предложенных предложениях, ответы на вопросы по содержанию текста. Большое внимание уделено активизации лексического материала в речевых высказываниях по изучаемой тематике путем выполнения заданий на выбор правильных или неправильных утверждений с последующей аргументацией, в обсуждении прочитанного материала в группах.
Применение ИКТ (видео, интернет-ресурсы) в данном учебном пособии способствует более эффективному изучению предметной области на иностранном языке.
В пособии также предусмотрен блок для дополнительный текстов для самостоятельного чтения, перевода, реферирования и аннотирования текстов.
Автор выражает признательность Филиновой Елене Федоровне за материалы использованные при создании данного учебного пособия.
Content
| стр. | |
| Введение | 4 |
| Содержание | 5 |
| Unit 1 | 6 |
| Text 1. METALS AND THEIR PROPERTIES | 6 |
| Text 2. IRON AND STEELS | 10 |
| Video “How to Make Steel” | 13 |
| Text 3. THE IRON PILLAR FROM DELHI | 15 |
| Unit 2 | 17 |
| Text 1. THE WORLD OF WELDING | 17 |
| Text 2. WELDING | 19 |
| Text 3. HISTORY OF WELDING | 21 |
| Text 4. HISTORY OF WELDING IN THE BEGINNING | 24 |
| Unit 3 | 27 |
| Text 1. FORGE WELDING (PART 1) | 27 |
| Text 2. FORGE WELDING (PART 2) | 29 |
| Video “MIG Welding” | 32 |
| Text 3. ARC WELDING (1) | 33 |
| Video “How to Become an Electric Arc Welder” | 34 |
| Text 4. ARC WELDING (2) | 36 |
| Unit 4. | 38 |
| Text 1. CLASSIFICATION OF WELDING | 38 |
| Text 2. SHIELDED METAL ARC WELDING | 42 |
| Text 3. FIND OUT MORE ABOUT RESISTANCE WELDING AND ITS TYPES | 45 |
| Text 4. SPOT WELDING | 46 |
| Video “Resistance Welding” | 48 |
| Text 5. SEAM WELDING | 51 |
| Supplementary Texts | 53 |
| Список литературы | 63 |
UNIT 1.
| 1. Basic Level Text 1. METALS AND THEIR PROPERTIES 2. Higher level Text 2. IRON AND STEELS 3. Grammar: the Infinitive; as well as, rather than, in order to. 4. Video: HOW TO MAKE STEEL 5. Individual work Text 3. THE IRON PILLAR FROM DELHI |
Basic Level:
Exercise 1. Answer the following questions. Use the background knowledge.
a) What are metals?
b) What are the most valuable metal properties?
c) What metals are called common/ precious / rare?
d) Can you remember the most popular application areas of metals?
e) What role do metals play in our country?
Exercise 2.Give Russian equivalents to the following:
| · Chemical element | · To conduct |
| · Periodic Table | · Concentration |
| · Hammer | · Electricity |
| · Non-metals | · Basis |
| · Heat | · Volume |
| · Electrolysis | · Bone |
| · Mixture | · Strong |
Exercise 3. Read the words aloud. Pay attention to your pronunciation.
Luster, hydrogen, copper, ductile, gravity, pure, mixture, chemistry, liquid, malleable, alloy, potassium, lead, ancient, hafnium, characteristic, ornament, machine.
Text 1 Metals and their properties
Metal, a member of the largest class of chemical elements in the Periodic Table.
Approximately three-fourths of the elements are metals. Most metals are silvery in color, have a characteristic luster, and are solid (rather than liquid or gaseous). Most metals are also malleable (can be shaped with a hammer), ductile (can be drawn into a wire), and good conductors of both heat and electricity.
However, some nonmetals also have these physical properties, while some metals lack one or more of them. A few metals—such as antimony and bismuth—are brittle rather than malleable. Carbon, a nonmetal, conducts heat as well as indium does and better than bismuth. Mercury is not solid at room temperature. Iodine, a nonmetal, has a metallic luster. Copper and gold are not silvery in color. It is therefore difficult to make a clear-cut distinction, on the basis of physical properties, between metals and nonmetals.
Chemically, metals are elements that are electropositive; that is, they tend to form positive ions when they undergo electrolysis. However, hydrogen, a nonmetal, also has this characteristic.
The heaviest metal is iridium, which has a specific gravity of 22.6 (that is, it has 22.6 times the weight of an equal volume of water). Lithium, the lightest metal, has a specific gravity of 0.53. Gold is the most malleable and ductile of the metals. Silver is the best conductor of heat and electricity.
Metals are found mainly in ores, which are mined in a variety of ways. An ore may either have the metal present in elemental form or in compounds. The process used to refine the ore depends on the form and concentration of the metal.
Metals are used both in pure form and in alloys. An alloy is a mixture of a metal and other metals or nonmetals. (An alloy of mercury and another metal is called an amalgam.) Most metal tools, machines, ornaments, and structures are made of alloys.
Metals are essential to life. Calcium, which is necessary for strong and healthy bones, is a metal. Sodium, iron, and potassium, which are all metals, are also considered necessary to the body.
Some metals—gold, silver, lead, tin, mercury, iron, copper, and antimony—have been known since ancient times. Other metals, such as hafnium, rhenium, and lutetium, have been discovered in the 20th century.
https://ar.answers.yahoo.com/question/index?qid=20120112180601AAmFwca
Vocabulary:
| Luster – блеск Solid – твердый Liquid – жидкий Gaseous – газообразный Malleable – ковкий Ductile –вязкий To lack – испытывать недостаток Antimony – сурьма Bismuth – висмут Brittle – хрупкий Carbon – углерод Mercury – ртуть Copper – медь Gold – золото Silvery – серебристый a clear-cut distinction – четкое отличие | electropositive – электроположительный to undergo - подвергаться hydrogen – водород specific gravity – удельный вес ore - руда to mine – добывать in elemental form – в свободном виде compound – соединение to refine – очищать, обогащать pure – чистый alloy –сплав; (to alloy - легировать) Calcium – кальций Sodium – натрий Iron – железо Potassium – калий Lead - свинец |
Дата: 2019-07-24, просмотров: 594.
