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UNIT 6WELDINGI. Text A: «Welding», Text В: «Other types of welding» II. Famous People of Science and Technology: James Prescott Joule. Text A: «WELDING»Welding is a process when metal parts are joined to gether by the application of heat, pressure, or a combi nation 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 riv eting 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 mo tor and aircraft industries. It is necessary almost in all productions where metals are used. The welding process depends greatly on the proper ties of the metals, the purpose of their application and the available equipment. Welding processes are clas sified 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 WeldingGas 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 weld ing methods. Arc welding is faster because the concen tration 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-tung sten 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 con nected 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 weld ing steels. Vocabulary: to join — соединять pressure welding — сварка давлением heat welding — сварка нагреванием instead — вместо, взамен bolting — скрепление болтами riveting — клепка basic — основной to manufacture — изготовлять to depend — зависеть от purpose — цель available — имеющийся в наличии equipment — оборудование source — источник gas welding — газосварка arc welding — электродуговая сварка resistance welding — контактная сварка laser welding — лазерная сварка electron-beam welding — электронно-лучевая сварка flame — пламя edge — край simultaneously — одновременно filler — наполнитель wire — проволока rod — прут, стержень to melt — плавить(ся) joint — соединение, стык advantage — преимущество to require — требовать нуждаться surface — поверхность coated — покрытый flux — флюс fusible — плавкий to shield — заслонять, защищать touching — касание tip — кончик General understanding: 1. How can a process of welding be defined? 2. What are the two main groups of processes of welding? 3. How can we join metal parts together? 4. What is welding used for nowadays? 5. Where is welding necessary? 6. What do the welding processes of today include? 7. What are the principles of gas welding? 8. What kinds of welding can be used for joining steels? 9. What does arc welding require? 10. What is the difference between the arc welding and shielded-metal welding? Exercise 6.1. Find the following words and word combinations in the text: 1. сварка давлением 2. тепловая сварка 3. болтовое (клепаное) соединение 4. процесс сварки 5. зависеть от свойств металлов 6. имеющееся оборудование 7. сварочный электрод 8. плавкий материал 9. дефектный сварной шов 10. непрерывная подача электрического тока 11. электрическая дуга 12. источник электрического тока |