Electron Beam Welding
Electron beam welding is associated with the beam welding methods in DIN EN 14610. According to DIN 8580 and DIN 8593-6 it is classified in the subgroup 22.214.171.124 as fusion welding by radiation.
The electron beam is an established tool for material processing in melting, drilling and welding processes. During thermal joining the process-specific features, such as high power density of about 107 W/cm-2 in the beam focus, the high efficiency and the process environment at a reduced ambient pressure of> 10-4 mbar are to call.
The resulting technical advantages over other fusion welding processes are very good surface properties of the weld, a small component distortion and a good control of the beam parameters.
Deep Penetration Welding
When striking of the up to 2/3 light-velocity accelerated electrons on the workpiece surface they transfer their kinetic energy into heat. Due to the mentioned high-power density of beam the material melt and vaporize. The developing vapor is overheated (ca.2700K) and the pressure is sufficiently high to press the material down and towards the sides. Thus the electron beam can impinge on material which is solid and heat it further. That forms a capillary which consists in its core of overheated vapor and is covered by a casing of molten metal.
The formation of this vapor channel is the reason for the typical appearance of the electron beam welds. At this point it should be mentioned that this so called „deep-penetration“ effect works with every metal. Even with metals which have high melting temperatures like tungsten and platinum or high heat conductivity like gold, copper an aluminum.
Electron beam welding is one of the widely used processes in industries for joining dissimilar materials. Due to the very fine beam (less than 100µm) and the ability of an exact positioning, with the SEM mode, the composition of the melt can be controlled. This avoids incomplete side wall fusion and an uncontrolled growth of inter-metallic phases which would lead to cracks. In (b) you see some examples of dissimilar welds: aluminum to copper, stainless steel to kovar and nickel-base-alloy to carbon steel.
Multiple Beam Technique
This is basically the technique behind all surface modification processes but can also be used to pre- or post-heat a workpiece.
Another application is the welding of radial joints. Due to the multiple beam technique it is possible to minimize or even avoid distortion.
Electron beam brazing combines the high quality of vacuum furnace brazing and the high productivity of laser-brazing. Especially with brazing of different materials, e.g. like TiAl with carbon steel, the synergy-effects of a good wetting behavior and a selective heat-input can be used.