Operating the camera.
Due to the need of vacuum in the chamber, where is formed and shaped the flow of electrons, in most cases, the electron-beam welding, and the product itself is placed inside a vacuum chamber to eliminate the scattering of electrons by atoms and molecules of gases. It also provides good protection of the weld metal. But on the other hand, it severely limits the possibility of applying this method of welding is mainly due to size limitations of welded products, and low productivity of the process, because a lot of time spent on the preparation of parts for welding. Therefore, along with high-vacuum equipment developed and those in which the electron beam is derived from the gun camera, which supports * a high vacuum, and the welding is done in a low vacuum (10-2 - 10-1 mm Hg. Art.).
Special units to develop microwelding in the manufacture of modular elements, and various kinds of solid radio circuits. Features are primarily in the exact dosage of thermal energy, the beam moves the product through the deflecting electric and magnetic fields, the combination of several technological functions performed by an electron beam in the same cell. Since the vacuum chamber in vacuum systems are the most expensive, the rationality of their choice * designs received much attention.
All of the existing structures can be divided into the condition of the following groups: 1) universal set of products for the welding of medium size, 2) universal and specialized for microwelding small parts; 3) Specialized systems for welding products for small and mid-size 4) set for the welding of large products with a complete seal, 5)-arc of large products with partial sealing of the joint space, 6)-arc in the intermediate vacuum.
Plants of the first group are mainly for use in research and industrial laboratories and in industry for the unit and small batch production. They have a vacuum chamber volume 0,001-4,0 m, and manipulators for moving the workpiece to allow universal movement as possible in the performance of welded joints. Such plants also supply surveillance systems field welding. The electron gun stationary or moves within the chamber to the initial installation of the beam at the joint.
Settings for the welding of large parts distinguished by the presence of expensive vacuum chambers where large amounts of items are placed entirely. Most electric guns that are much smaller than the product is placed inside the chamber. The weld is performed by moving the electron gun itself. Sometimes, especially when welding the two seagulls annular sutures are placed on the camera allows multiple guns by eliminating the longitudinal movement of goods and reduce the size of the camera.
In order to reduce hardware costs and increasing productivity plants do sometimes last only a local evacuation of the welded joint. Then the pumped volume is reduced, the size of the installation as a whole also obtained less than if all of the product placed in the chamber. Sometimes, for example, when welding pipes when they are laying directly, without the local vacuum, to solve the problem is not possible. In some cases, the working chamber of the installation can be pumped only to the intermediate vacuum (10-1 - 10 -2 mm Hg. Art.). The diffusion pump for pumping the working chamber becomes unnecessary (for the camera gun, he is still required, but the low power and small size). In such installations lucheprovod connecting the camera to the camera gun parts, design, taking into account a desired pressure differential between the chambers, and sometimes even in the lucheprovode provide an intermediate stage of pumping. In the cathode-ray installations particularly important to the accuracy of manufacture and assembly of welded parts and the tracing of the situation beam relative to the welded joint. In tracking systems use the secondary-emission detector, which converts the signal from the electron beam and directs at the junction with the deflection coils. principle of such a system is as follows. After contact with the electron beam on the metal surface of the secondary electrons are knocked out of the last flying in the opposite direction to the camera. Postavlenyny on their way to the sensor identifies a signal proportional to their number, and sends it to the system controlling the position of the beam. The number of secondary electrons depends on the condition and shape of the metal surface on which the beam. Their number is maximum for a smooth surface, perpendicular to the beam, and decreases when the beam crosses the irregularities. After contact with the beam in the deep cavity number of secondary electrons is reduced to almost zero, since they are absorbed by the cavity walls. developed to monitor the beam position with respect to the joint system of the type "weather" works as follows. Beam, welded metal, occasionally with a frequency of 20-50 Hz output from the bath, at a high speed crosses the junction before the weld pool (at a distance of 5-7 mm) and immediately returned. The output beam from the bath is so short-lived that the parameters of the joint is not affected. When crossing the beam junction is an abrupt change in the signal of secondary electrons. The position of this pulse is compared with the position of the beam in the absence of current in the deflection system and if necessary, automatically adjusts itself during the welding process. This system provides accurate tracking of the junction, calculated in hundredths of a millimeter, and is extremely fast. In the system, "forecast" laid the blocks that allow you to control movement of the beam, necessary in terms of technology: to weld with longitudinal, transverse and circumferential variations of the beam, performed with different given speed and a different law.
See also:
Electron Beam Welding Technology
Electron Beam Welding Article
Installations for Electron Beam Welding
Electron Beam Welding Gun
Work Chambers for EBW
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