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Mechanical Engineering

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Mechanical Engineering

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  1. Electron Beam welding (EBW) New technology for “clean welds” principles : high velocity e-are emitted & directed towards the metal from, a tungsten that is heated to 22000C e-pass through a magnetic field • Centred by the anode and deflecting coils • The e-beam is produced in vacuum. High purity of the weld. (also, fusion temperature is lower for the metal/ forall materials) High penetration of e-beam • Depth to width ratio of weld is 25:1and the beam is 0.8 –3.2 mm DIA.(could be made much smaller) • Low heat input, low distortion, narrow heat affected zone high purity of weld is assured

  2. Electron Beam Welding is a fusion welding process in which a beam of high-velocity electrons is applied to the material to be joined • The work-piece melt as the kinetic energy of the electrons is transformed into heat upon impact • The EBW process is well positioned to provide industries with highest quality welds and machine designs that have proven to be adaptable to specific welding tasks and production environments

  3. Electron Beam

  4. Electron Beam • In an electron beam welder electrons are “boiled off ” as current passes through filament which is in a vacuum enclosure • An electrostatic field, generated by a negatively charged filament and bias cup and a positively charged anode, accelerates the electrons to about 50% to 80% of the speed of light and shapes them into a Beam

  5. How does the Process Work ? • The electron beam gun has a tungsten filament which is heated, freeing electrons • The electrons are accelerated from the source with high voltage potential between a cathode and anode • The stream of electrons then pass through a hole in the anode. The beam is directed by magnetic forces of focusing and deflecting coils • This beam is directed out of the gun column and strikes the work piece. The potential energy of the electrons is transferred to heat upon impact of the work piece and cuts a perfect hole at the weld joint. Molten metal fills in behind the beam, creating a deep finished weld

  6. Steps Used in EBW process • Joint preparation • Cleaning of work piece • Fixturing of work piece • De-magnetization of work piece • Setting up work piece in chamber • Pump down air form chamber • Carry welding process

  7. EBW is suitable for a variety of difficult applications, such as welding structures on which the reverse side of the butt is inaccessible ; gravity welding of thin metal ; and welding in various spatial positions • This Provides a low level of over all heating of the structures ; and has the ability to vacuumed the inner volume simultaneously, which is suitable for sealing instruments. Because EBW is an automated process , the welded joint quality is consistent • The process does not require shielding gases , tungsten electrodes , or edge preparation for welding thick metal • Finally , it can be used to weld some joints that cannot be made by other welding processes.

  8. Compared with arc welding processes, EBW improves joint strength 15 per cent to 25 per cent • It has a narrow heat-affected zone (HAZ), which results in lighter-weight product

  9. Geometric shapes and dimensions are highly stable, particularly when it is used as a finish operation • It eliminates oxide and tungsten inclusion sand removes impurities • The weld metal has a fine crystalline structure

  10. In Vacuum a) Thin and thick plate welding (0,1 mm bis 300 mm) b) Extremely narrow seams (t:b = 50:1) c) Low overall heat input => low distortion =>Welding of completely processed components d) High welding speed possible e) No shielding gas required f) High process and plant efficiency g) Material dependence, often the only welding method At atmosphere a) Very high welding velocity b) Good gap bridging. No problems with reflection during energy entry into work piece Advantage of EBW

  11. In Vacuum • Electrical conductivity of materials is required • High cooling rates => hardening => cracks • High precision of seam preparation • Beam may be deflected by magnetism • X-ray formation • Size of work piece limited by chamber size • High investment At Atmosphere • X-ray formation • Limited sheet thickness (max. 10 mm) • High investment • Small working distance Disadvantage of EBW

  12. Field of Application • Automotive industries • Aircraft and space industries • Mechanical engineering • Tool construction • Nuclear power industries • Power plants • Fine mechanics and electrical • Industries • Job shop

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