Гричин С.В., Ульянова О.В. - Английский язык для инженеров сварочного производства (1044906), страница 20

Просмтор этого файла доступен только зарегистрированным пользователям. Но у нас супер быстрая регистрация: достаточно только электронной почты!

Текст из файла (страница 20)

На борту космического корабля исследователи изучали поведениерасплавленного металла и особенности его кристаллизации в условияхкратковременной микрогравитации.2. Технологии космической сварки шагнули далеко вперед.3. Одна из задач, решаемых с помощью сварки в открытом космосе, –профилактическое обслуживание и ремонт оборудования космическогокорабля.4. Разнообразие используемых материалов и невысокая энергоемкостьоборудования являются решающими факторами, обусловливающимивозможность использования сварки в открытом космическомпространстве.5.

Дальнейшее освоение космического пространства потребуетусовершенствования практически всех видов сварочных технологий, атакже резания, пайки и нанесения покрытий.1106. Специфика используемого на космических кораблях оборудованияобусловливает необходимость использования, прежде всего, ручнойсварки при частичной автоматизации процесса.7. Электроннолучевой ручной сварочный аппарат прошел успешныеиспытания на орбитальном комплексе в условиях открытого космоса.8. Использование новейших материалов в следующем столетиипотребует разработки совершенно новых технологий получениянеразъемных соединений.Reading 27You will read the text What Is Orbital Welding.

Before you read thinkand say why this type of welding is called “orbital”. Read the openingparagraph and check your supposition.Read the text and say what the main advantages of this method are.What Is Orbital WeldingThe term Orbital-Welding is based on the Latin word ORBIS = circle.This has been adopted primarily by aerospace and used in terms of Orbit(noun) or Orbital (adjective) for the trajectory of a man-made or naturalsatellite or around a celestial body. The combination Orbital Weldingspecifies a process by which an arc travels circumferentially around a workpiece (usually a tube or pipe). The concept Orbital Welding is basically aloosely defined term that is usually used for processes only, where the arc istravels at least 360 degrees around the work piece without interruption.Consequently, processes, which interrupt the full 360-weld sequence such asfor better puddle control (often used for MIG/MAG welding, using the downhand welding sequence in 2 half-circles), can not truly be called orbitalwelding.Possibilities and LimitationsFrom welding terminology Orbital Welding belongs to the categorysemi-mechanized (TIG-) welding.

Because of the need for good control of theweld puddle, the Orbital-Welding process is only practiced with the TIGprocess and relevant rules like selection of gases, cleanness, weldability ofspecific materials and consequential mechanical strength specifications suchas tensile and bend loading, are very important.Orbital-welding is presently used whenever the quality of the weldjoint has the highest priority. These demands are not only limited tomechanical strength and X-ray qualification, but also to the important aspects111of the aesthetics of the weld seam.

For any users a uniform, flat and smoothroot-pass is the main reason for using this process. Consequently, it isfavoured in the following areas: chemical industry, pharmaceutical industry,bio-technology, high-purity water systems, semiconductor industry, aircraftand aerospace industry. Moreover, because of the weld joint's uniformoutside shape and almost complete absence of need for any post-polishing,Orbital-welding is even used for bends on door-handles, hand-guards, or indead foot-elements for champagne-glasses! Interested applicants for thistechnology should certainly note that they have to confirm a couple ofindispensable premises.The following presents the basic rules for this process, valid for allmanufacturers and systems.Even knowing that some competitors are announcing features, which wouldpotentially violate the basic physical laws of nature and knowledge,moreover, making promises and statements which are at least detected asimpossible to meet when the welding system must work under high dutycycle production conditions.

Indiscriminate and exactly defined dimensionswith tolerances must be thorough and complete. The much liked standpoint,that the welded tubes and pipes are in accordance to DIN or ASME standardsare not acceptable criteria. These qualifications only define tolerances inpercentage to the wall thickness relating to pressure loading and not toweldability using the Orbital-Welding-Process.For the Orbital-Welding-Process absolute tolerance values arenecessary, and furthermore, the more complicated the application, the tighterthe tolerances must be. This means, that for an easy application like weldinga stainless steel tube of 53 x 1,5 mm, a tolerance in alignment of about 0,5mm (about 30% of the wall thickness) can be compensated, but for muchmore critical applications like welding a carbon-steel pipe of 114,3 x 3,6 mm,the same percentage can result in unacceptable weld quality.

Therefore, thequestion of acceptable tolerances should be researched and defined for eachapplication individually.That Orbital-Welding can be used successfully and economically isproven by the constantly increasing number of users. Field experience hasshown that Orbital-welding can be justified based upon economic reasonsalone, where the welds can be done in squared-butt no-gap preparationutilizing a single pass.

With advanced digital welding systems this is possibleup to a wall-thickness of 4 mm, and with welding systems with lowerperformance capabilities (limited levels, no pulse-synchronized cold-wirefeeding), up to 3 mm.Joint preparation is simple but requires high quality with an exact90\'b0 angle to the tube/pipe axis; a high quality saw cut is usually enough.112Of course, the joints should be deburred and cleaned out of corrosion, oil,tinder, etc. With appropriate quality-demands, this should be even obviousfor manual welds! The tube joints will be then fit together without any visiblegap. This can be done with small autogenous tack-welds or with internal orexternal clamping fixtures. For larger wall-thickness it is necessary to bevelthe weld-joints, far as possible in a U-shape.

Since a very precise anduniform root pass is important, a weld joint is prepared with an. I.D. relatedand fixed bevelling-machine. Manual grinding or the use of bevelling sawblades is not precise enough for repeatable welding results. Because anOrbital-Welding job usually requires a lot in time and money, the Orbitalmulti-pass-welding is not used very often and only where it is strictlyrecommended on quality reasons.

A good qualified manual welder will, inmost cases, be faster than an Orbital-welding-system. Additionally, anOrbital-system for multi-pass welds will be much more expensive and evenmore complicated than a system without this option.Visual inspections of the weld-seam clone can never be sufficient asthe sole criterion. Other quality controls, such as, corrosion, consistency,mechanical strength must also be considered. Also, allowed tolerances incontents of alloys on specific materials, such as sulphur content, can result insignificantly different welding results, even when the material code is thesame. Usually, you can expect that stainless steel materials up to 3 mm wallthickness can be done without filler-wire.

For higher wall-thicknessapplications, you have to decide on a case-by-case basis. In someeventualities even carbon steel can be done without filler-material, althoughit's even recommended on the thinner wall-thickness to use filler-wire in anyway.Vocabularydown-hand weldingcelestial bodybend loadwelding sequencetensile loadpressure loadroot passtolerancemanual weldingpost-polishingсварка в нижнем положениинебесное телонагрузка на изгибпоследовательность сварки, порядокналожения швоврастягивающая нагрузкасжимающая нагрузка, усилие сжатиякорневой шов, проход, сварка корневогошвадопускручная сваркапоследующее полирование113tack weldX-ray testing(qualification)high dutyclamping fixtureDINIDU-shape (bend)grindingweld seamfiller wiresaw bladebevellingperformance capabilitiesприхваточный сварной шов, прихваткарентгеновская дефектоскопияжесткий режимприжимное устройствонем.

Характеристики

Список файлов книги