Electron Beam Welding EBW
In electron beam welding, coalescence of metals is achieved by heat generated
by a concentrated beam of high-velocity electrons impinging on
the surfaces to be joined. Electrons have a very small mass and carry a
negative charge. An electron beam gun, consisting of an emitter, a bias
electrode, and an anode, is used to create and accelerate the beam of
electrons. Auxiliary components such as beam alignment, focus, and
deflection coils may be used with the electron beam gun; the entire
assembly is referred to as the electron beam gun column.
The advantages of the process arise from the extremely high energy
density in the focused beam which produces deep, narrow welds at high
speed, with minimum distortion and other deleterious heat effects.
These welds show superior strength compared with those made utilizing
other welding processes for a given material. Major applications are
with metals and alloys highly reactive to gases in the atmosphere or
those volatilized from the base metal being welded.
A disadvantage of the process lies in the necessity for providing
precision parts and fixtures so that the beam can be precisely aligned
with the joint to ensure complete fusion. Gapped joints are not normally
welded because of fixture complexity and the extreme difficulty of
manipulating filler metal into the tiny, rapidly moving, weld puddle
under high vacuum. When no filler metal is employed, it is common to
use the keyhole technique. Here, the electron beam makes a hole entirely
through the base metal, which is subsequently filled with melted
base metal as the beam leaves the area. Other disadvantages of the
process arise from the cost, complexity, and skills required to operate
and maintain the equipment, and the safety precautions necessary to
protect operating personnel from the X-rays generated during the operation.

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