Урок 4 Тема. Чёрные и цветные сплавы
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Упр. 18. Выполните следующее задание
Упр. 19. Переведите текст “Hardfacing” на русский язык, пользуясь словарём. Выполните следующие за текстом задания. HardFacing Hardfacing is the process of applying by welding, plasma spraying or flame plating a layer, edge or point of a wear-resistant metal on a metal part to increase its resistance to abrasion, erosion, hammering or other forms of wear. Hardfacing may be applied to new parts to improve their resistance to wear during the service or to worn parts for the purpose of restoring them to the serviceable condition. In general the wear-resistant coating is applied only to those critical surfaces of components where wear is maximum. Worn parts can be satisfactorily refaced or rebuilt many times before the replacement becomes obligatory. Alloys, which are used for hardfacing should possess the following properties:
Both ferrous and non-ferrous alloys are used for hardfacing. They are: austenitic manganese steel, cobalt-base alloys, aluminium bronzes, beryllium copper alloys. Of the latest use titanium carbides should be mentioned specially because of their high properties. Powder Alloys. Many of the alloys available for hardfacing are produced as powders. Some of the powders are used for spray-coating processes for protecting metal surfaces but high percentage of powders are pressed and sintered approximately to the final shape that then can be machined to a desired shape. Задание 1.
Задание 2. Прокомментируйте следующие тезисы, используя выражения из задания 2 стр. 22 (урок 2).
Приложение Text 1. How Steels are Classified spring [sprIN] n – пружина retain [rI'teIn] v – сохранять Steels are classified in several different ways. The primary method of classification is by the carbon content or by the content of alloying elements other than carbon (which is present in every steel), i.e. by the chemical composition of steels. Carbon steels. When we refer to “carbon” steel, we mean the steel which contains iron, carbon, less than 1.65% manganese, less than 0.6% copper, and small amounts of silicon, sulphur and phosphorus. Sulphur and phosphorus are considered impurities, and not more than 0.05% of either is allowed by specifications, except some cases. The amount of manganese may range from as little as 0.35% to as much as 1.65%. The family of carbon steels (it is a large family with nearly 50 standard grades) is usually sub-divided into four sub-families: the 1оw-carbon steels which contain no more than 0.3% carbon; the medium-carbon steels, which range from 0.30 to 0.45% carbon (0.25 – 0.50%); the high-carbon steels from 0.45 to 0.75% carbon; and the very-high-carbon steels, which range up to 1.5% carbon. The low-carbon steels often termed "mild" steels are more widely used than the grades with a higher carbon content. They are quite ductile and can be machined or formed quite easily and can be welded by any process. As the carbon content increases, tensile strength and hardness increase, but ductility reduces, and machining of the steel may become more difficult. The very-high-carbon steels are used principally for springs and tools which are used to cut or form metals. High-carbon and very-high-carbon steels are seldom welded; when welding must be used, the metal must be heat-treated before, during and after welding if sound welds are to be obtained and the desired mechanical properties of the steal retained. Alloy steels. Any steel which contains more than 1.65% manganese, or 0.60% copper or a guaranteed minimum amount of any other metal is termed an "alloy" steel. The metals most frequently used for alloying purposes are nickel, chromium, molybdenum, vanadium and manganese. In the group of alloy steels usually termed "high-strength" alloys, the addition of small amounts of nickel, chromium or molybdenum (less than 1%) raises tensile strength considerably. Although these steels cost more than plain carbon steels, steel costs for structures specifically designed to utilize their higher strength are less than the steel costs for equally strong structures designed in terms of plain carbon steels. Задание 1. Составьте аннотацию текста. Задание 2. Прокомментируйте следующие тезисы, используя выражения из задания 2 стр. 22 (урок 2).
TEXT 2. TOOL STEELS A tool steel is any steel used to make tools for cutting, forming or shaping a material into a part or component adapted to a definite use. The earliest tool steels were simple plain carbon steels. Now complex alloy steels are used for this purpose. Alloy steels contain relatively large amounts of tungsten, molybdenum, manganese and chromium, which make it possible to meet increasingly severe service demands. Many alloy tool steels are also widely used for machinery components such as high-temperature springs, special-purpose valves, bearings of various types for elevated-temperature service. In service, most tools are subjected to extremely high loads that are applied rapidly. They must withstand these loads a great number of times without breaking and without undergoing excessive wear or deformation. Most tool steels are wrought products, but precision castings can be used in some applications. The powder metallurgy process is also used in making tool steels. The performance of a tool in service depends on proper design of the tool, accuracy with which the tool is made, selection of the proper tool steel and application of the proper heat treatment. Almost all tool steels must be heat treated to develop specific combinations of wear resistance, resistance to deformation or breaking under high loads and resistance to softening at elevated temperatures. Задание 1. Составьте аннотацию текста. Задание 2. Прокомментируйте следующие тезисы, используя выражения из задания 2 стр. 22 (урок 2).
TEXT 3. Stainless steels staining ['steInIN] n – коррозия пятнами utensils [jH'tensIlz] n – утварь cold work n – холодная обработка fasteners ['fRsnqz] n – крепёжные детали cutlery ['kAtlqrI] n – ножевые изделия hardware ['hRdwFq] n – металлические изделия dairy ['dFqrI] a – молочный Stainless steels are more resistant to rusting and staining than plain carbon and low-alloy steels. They have superior corrosion resistance because they contain relatively large amounts of chromium. Stainless steels may be defined as alloy steels containing at least 10% chromium – with or without other elements. Improvements in melting technology have led to the production of alloys with very low carbon contents and remarkable freedom from nonmetallic inclusions. Inert-atmosphere melting techniques and vacuum remelting processes have made it possible to produce stainless steels with carbon levels below 0.010%. Mechanical properties of most stainless steels, especially ductility, toughness are higher than the same properties of carbon steels. Strength and hardness can be raised by cold work and by heat treatment for different types of stainless steels. Corrosion resistance frequently is the most important characteristic of a stainless steel. Uniform corrosion is often much less serious than localized forms such as stress corrosion cracking, crevice corrosion and others. Such localized corrosion can cause unexpected and sometimes catastrophic failure. At elevated temperatures attack can be accelerated significantly. Despite these complications a suitable steel can be selected for most applications on the basis of experience. Over the years, stainless steels have become firmly established as materials for cooking utensils, fasteners, cutlery, decorative architectural hardware and equipment for use in chemical plants, dairy and food processing plants, health and sanitation applications, petroleum and petrochemical plants, in transportation industry, in medicine. Задание 1. Составьте аннотацию текста. Задание 2. Прокомментируйте следующие тезисы, используя выражения из задания 2 стр. 22 (урок).
TEXT 4. COPPER aqueous ['eIkwIqs] a – водяной; содержащий воду vehicle ['vJIkl] n – перевозочное средство Copper and its alloys have been in the service of mankind for longer than any other metal, and until the second half of the 20th century it had the largest use of any metal after iron. Aluminium has now taken the second place and copper is the third. Copper and zinc with addition of alloying elements form brass, copper and tin – bronze. Copper and its alloys are widely used because of their excellent electrical and thermal conductivities, outstanding resistance to corrosion, and ease of fabrication, together with good strength and fatigue resistance. They are generally nonmagnetic. They can be readily soldered and brazed, and can be welded by various gas, arc and resistance methods. Pure copper is used extensively for cables and wires, electrical contacts, and a wide variety of other parts that are required to pass electrical current. Copper and certain brasses, bronzes and cupronickels are used for absorbing solar energy. Because of their outstanding ability to resist corrosion, copper and its alloys are used for pipes, valves and fittings in systems carrying water, or other aqueous fluids. The chief customer industries are the building construction, the electronics, the automobile industry, the chemical and petrochemical industries, the electrical engineering, transportation applications including road vehicles, railroad equipment and aircraft parts and so on. Задание 1. Составьте аннотацию текста. Задание 2. Прокомментируйте следующие тезисы, используя выражения из задания 2 стр. 22 (урок 2).
TEXT 5. NICKEL AND ITS USES sword ['sLd] n – меч, шпага, сабля arrowhead ['xrouhed] n – наконечник стрелы nodule ['nOdjHl] n – геол. конкреция Nickel alloys were known and used for thousands of years before nickel was isolated and identified as an element. The use of iron-nickel alloys of meteoric origin by primitive man has been well documented. The legendary swords of Damascus, often described as being "heaven-sent", probably were made from iron-nickel meteorites. Alloys of copper and nickel were used by the ancient Chinese to make such objects as coins, swords and arrowheads. Nickel is a hard, tough and malleable silver-white metal that has good resistance to oxidation and corrosion. It is used principally in association with other elements to impart strength, toughness and corrosion resistance to a wide range of ferrous and nonferrous alloys. Nickel, like iron and cobalt, is magnetic, and thus nickel alloys are often used in magnetic applications. Pure nickel in native form is unknown and nickel ores are widely distributed on the earth. Nickel is present in significant quantities in the ocean, particularly in deep-sea nodules that contain nickel, copper, cobalt and manganese. The vast majority of nickel ore came from three countries – Canada, Russia and New Caledonia. Of the total amount of nickel consumed, about 55% ordinarily is used as alloying additions to stainless and alloy steels. About 20% of nickel is used in nonferrous alloys where nickel is the major component in a large number of nickel-base, cobalt-base and copper-base alloys. About 10 – 15% of nickel is used for electroplating. Nickel plating, a standard coating used for decorative purposes, is also widely used for its ability to protect other metals from wear and corrosion in industrial applications. Задание 1. Составьте аннотацию текста. Задание 2. Прокомментируйте следующие тезисы, используя выражения из задания 2 стр. 22 (урок 2).
TEXT 6. ALUMINIUM missile ['mIsaIl] n – ракета missile a – ракетный tank [txNk] n – резервуар, ёмкость In terms of production and consumption, aluminium is second only to iron as the most important metal of industry used today. Next to oxygen, aluminium is the most abundant element in nature: about 7.45 per cent of the earth's crust consists of aluminium. So the resources from which aluminium is extracted are practically inexhaustible. Aluminium is the third most abundant metal in the earth's crust, almost twice as abundant as the next metal, iron. Aluminium is probably best known for two properties – light weight and corrosion resistance. Its specific weight is only about 2.7. It has excellent resistance against corrosive elements in the atmosphere, water (including salt water), oils and many chemicals. Besides, aluminium is a strong metal. Some aluminium alloys exceed structural steel in strength. Aluminium is being used increasingly in static structures such as buildings, bridges, towers and large field storage tanks. As is known, steel structures are lower in cost, but aluminium structures are used where light weight is a major consideration. Aluminium and its alloys have high electrical and thermal conductivities, so they are used in electrical- and radio-engineering. Aluminium is used in automobiles for components of various engines. Aluminium is used in many segments of the aircraft, the missile and spacecraft industry – in airframes, engines, propellers; tanks for liquid fuel and oxidizers; in household electrical appliances – vacuum cleaners, electric irons, food mixers; for food-handling equipment; furniture; cooking utensils; chemical process equipment, the petroleum industry; textile equipment; different tools and instruments. |
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