Electron beam welding: technology, equipment, features and operating principle

This welding method first appeared in 1958. Electron beam welding allows metals to be welded together. Electron beam welding involves joining two metals at their junction. It is performed in a vacuum and welds parts of a wide variety of designs and sizes, producing a highly polished weld.

The kinetic energy of electrons collected in an electron beam, which is formed by a special device, is used to join metal. The metal is welded using a pulsed beam. This beam has a very high energy density, and the pulse frequency ranges from 100 to 500 Hz. It is used for welding volatile metals such as magnesium and aluminum. With these parameters, penetration depth increases. Metal of various thicknesses can be welded, but the type of metal, its thickness, and structure must always be taken into account.

Thin sheets can also be successfully joined, but a test run is performed before the welding process to correctly establish the pause-to-pulse ratio. Heat dissipation during pauses helps reduce the size of the heat-affected zone. When welding small parts, it is crucial that the beam accurately hits the narrow seam width, so the beam position is first checked on a test sample. The beam must precisely hit the seam being joined, neither too low nor too high, otherwise the joint will not produce a high-quality result. Beam parameters are verified through a process experiment. After this, serial welding of all necessary parts is performed.

In electron beam welding, the beam itself or the workpiece is moved using a deflection system. This system allows the beam to oscillate across and along the weld, as well as along more complex trajectories. Low-voltage and high-voltage units are available. Low-voltage units are used for welding metal thicknesses of 0.5 mm and above, while high-voltage units are used for thicker metal.

The vacuum created in electron beam welding significantly reduces electron kinetic energy loss due to collisions with air gas molecules and provides thermal and chemical protection for the cathode in the electron gun. The vacuum is approximately 10-4 to 10-6 mmHg. Metal penetration occurs primarily due to the pressure of the electron beam, the heat released within the solid metal, and the powerful pressure of the evaporating metal. The quality and type of beam processing depend on the thermophysical properties of the material, the beam parameters, and the pulse duration, but is independent of the mechanical properties of the material. Therefore, electron beam welding can process quartz, ceramics, and precious stones. It is successfully used for welding refractory metals, as well as metals used in the aircraft and instrument industries. Depending on the size of the vacuum chamber, it is possible to join thick parts.

Advantages of electron beam welding:

• It is possible to weld parts with a thickness from 0.1 to 200 mm in one pass, and under different conditions even thicker parts;
• the process is cost-effective, requiring 10-15 times less energy than arc welding;
• there is no gas saturation of the metal, which gives strength to the weld;
• high quality welds, deep metal penetration.

Disadvantages of this type of welding:

• at the root of the seam there is sometimes an undercooked seam;
• attachment to the working chamber to create a vacuum.