Depth of weld

Metalograpics cross-section of welding sample

The depth of penetration of electron beam into material (in solid state) depends on more factors. The most important of them are the total power of the beam and the power density in the cross-section of the beam (the focusation). It also depends on position of the „cross-over“ (focus) relative to the surface (deeper penetrations are achieved with slightly "under-focused beam). Furthermore the weld depth depends on physical properties of the material and welding speed. On energy of electrons in the beam (accelerating voltage) the penetration depends only indirectly, so that at higher voltages higher values of power density are achieved.

Thanks to the improvements of our equipment we have succeeded to increas the depth of penetration in stainless steel from previous 10 mm to 15 mm, with a beam of 2 kW at 60 kV.

Take notice in attached photo of metalografic cut that the ratio of width to depth of the remelted zone is rather small, about 1:11. It is also worth mentioning that the deepest penetration has been achieved with the lowest focusing current (800–15 mA) while the other parameters (beam energy 60 keV, beam current 33 m and circumferential speed 10 mm/s) have been kept constant. Only two test welds have been realized with 50 kV (39 mA beam current) due to cathode failure. Nevertheless, the comparison of these two welds with similar made at 60kV shows the differences (lower depth and greater width).

Fig. 1:Section of a test sample.Fig. 1:Section of a test sample. Fig. 2:Seams of test welds.Fig. 2:Seams of test welds. Fig. 3:Metallographic section of test welds.Fig. 3:Metallo­graphic section of test welds.