The working principle of electron beam welding in pvd coating machine is: under vacuum conditions. The electron beam emitted from the electron gun is accelerated at a high voltage (usually 20 ~ 300kV) and focused into a high energy density electron beam through an electromagnetic lens. When the electron beam bombards the workpiece, the kinetic energy of the electrons is converted into heat energy, and the local temperature of the welding area can suddenly rise to more than 6000 ° C. The workpiece material is partially melted to achieve welding.

Electron beam welding features:
① Large heating power density. The electron beam power is the product of the beam current and its accelerating voltage, and the electron beam power can be from tens of kW to more than 100 kW. The power of the electron beam spot (or focus) can reach 106 ~ 108W/cm2, which is about 100 ~ 1000 times higher than the arc power density. Due to the large power density of the electron beam, concentrated heating, high thermal efficiency, and small heat input required to form the same weld joint, it is suitable for the welding of refractory metals and thermal sensitive metal materials. Moreover, the deformation after welding is small, and the parts after finishing can be welded.
② Weld penetration depth width ratio (that is, depth width ratio) is large. The penetration width ratio of ordinary arc welding is difficult to exceed 2. The ratio of electron beam welding can be as high as 20 or more, so electron beam welding can use high-power electron beam to weld large thickness steel plate without opening the groove on one side. Thus, the technical and economic index of thick plate welding is greatly improved. At present, the maximum thickness of the single side electron beam welding steel plate is more than 100 mm, and the maximum thickness of the electron beam welding of aluminum alloy is more than 300mm.
③ High purity atmosphere around the molten pool. Because electron beam welding is carried out in a vacuum environment with a vacuum degree of 10-2 ~ 10-4Pa. The amount of oxygen and nitrogen present in the residual gas is about hundreds of times less than the purity of 99.99% argon, so the electron beam welding does not have the problem of oxidation pollution of weld metal. Therefore, it is particularly suitable for welding metals with strong chemical activity, high purity and easy to be polluted by the atmosphere (oxidation) at melting temperatures. Such as aluminum, titanium, zirconium, molybdenum, high strength steel, high alloy steel and stainless steel. This welding method is also suitable for high melting point metals and can be used for tungsten-tungsten welding.
Because the electron beam welding of the pvd coating machine is to heat the joint to the melting temperature with a focused high-energy electron beam (>10kV) in a vacuum, the heating area is very concentrated, so only small parts that can be placed in the vacuum room can be welded.