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Electron beam welding (EBW) is a fusion welding process that uses a narrow beam of high-energy electrons to melt material and create a weld that joins two pieces of metal. Electrons — negatively-charged subatomic particles — are accelerated until they reach 30 to 70 percent the speed of light. At this rate, the beam of electrons is able to heat the surfaces to be welded to the temperature needed. EBW is a form of low-pressure welding that requires a high-vacuum. The requirements of EBW make it one of the more expensive forms of fusion welding, but the quality and depth of weld make it the best choice for specific situations, such as some aeronautics applications.
Unlike some other forms of welding, electron beam welding does not require a “filler wire” — a filament of metal placed between the two pieces to be welded together. The entire weld is created from the metal of the pieces that are joined. The beam of the EBW is very narrow, allowing it to function in situations where minimal heating of the overall material is desired.
A vacuum is needed in order to create the beam in EBW. Usually, a series of chambers at varying levels can be used to create an EBW that can weld material outside of the vacuum. The low- or non-vacuum methods, however, may sacrifice the purity of the weld, as well as decreasing depth and increasing width.
There are a number of benefits to electron beam welding over other types of fusion welding. The greater depth-to-width ratio of EBW in a vacuum makes it well-suited to thick joints. The narrow run of the beam also helps to limit distortion of the welded materials by reducing the total surface that is heated. The size of the the weld may be more consistent than other types of welds, and EBW typically creates a stronger-than-average weld.
The nature of EBW may also make it useful in joining dissimilar metals. Electron beam welding may even work to join reactive metals — metals that readily react when heated — and refractory metals — metals that are heat-resistant, with a melting point exceeding 3000 to 3100°F (approximately 1650 to 1700°C).
The most prohibitive feature of electron beam welding is the cost of equipment, which is much more specialized than for other fusion welding techniques. There may also be high set-up costs prior to laying down the weld. The need to work inside of a vacuum may also prove limiting to the size of pieces that can be joined with EBW.