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NEWER TYPES OF WELDING METHOD - Electron - Beam Welding

 These types are called "newer" since these are not in use for many many years and have been developed very recently. The types are :

1.) Electron - Beam Welding 

2.) Laser - Beam Welding. 

Electron - Beam Welding And Its Process :

Electron beam welding utilizes the energy from fast moving beam of electrons focused on the work piece. The electrons strike the metal surface , which gives up kinetic energy almost completely into heat. The beam is created in a high vacuum (10^-3 to 10 ^-5 mm Hg). If the work is done is such vacuum, no electrodes, gases, or filler metals can contaminate it, and pure welds can be made. Moreover, High vacuum is necessary around the filament so that it will not burn up and will also produce and focus a stable beam. 

In all types of electron beam machines, a tungsten filament which serves as a cathode emits a mass of electron that are accelerated and focused to a 0.25 - 1mm diameter beam of high energy density up to 0.5 to 10 kW / mm2. The heat generated is about 2500*C. This is sufficient to melt and vaporize the workpiece material and thus fills a narrow weld gap even without a filler rod (although filler rods may be used).

The speed of the beam is stepped up to one-half to two-thirds of the speed of the light by passing it through a high-voltage electrostatic field. An electromagnetic lens is employed to obtain correct focusing of the beam.

Near Zero Pressure is necessary for the formation of the beam. The chamber is evacuated to a pressure to 10 mm Hg. Welding begins at this point. A similar processes, known as non vacuum electron beam welding is rapidly coming into use today. This means that many welds can now be made without elaborate arrangement required for vacuum electron beam welding. In that case, the vacuum chamber in which the beam is created is evacuated to a lower pressure. In situation where contamination of the workpiece must be held to minimum , the beam should be passed through argon or helium. To make the chamber high vacuum , it takes about 5 to 30 min to evacuate the air, depending on the size of the chamber. A medium size electron beam welder operates below 60 kV. The welding head or the work is moved by the numerical control or by hand. 

Today automobile, airplane, aerospace, farm and other types of  equipment including ball-bearing over 100 mm are being welded by the electron beam process.

The advantages of  EBW are that the welds are clean, with no porosity since there is no air ; so shielding gas is needed ; and as the energy input is in a narrow , concentrated beam, distortion is almost eliminated. The speed may be as fast as 2500 mm/min, and it will weld or cut any metal or ceramic , diamond, sometimes as thick as 150 mm. 


Electron Beam Welding


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