Penetration Depth in Electron Beam Welding (Report 1)

Observation of Growing Process of Penetration Depth Using Pulse Beam (Part 1)

Abstract

In electron beam welding, it is well known the drilling action of electron beam dominates shape of fusion zone. In order to study this action, rectangular type pulse electron beams were impinged on Al-Zn-Mg alloy and shape of fusion zones were observed. Experiments were carried out using both rest and moving metals varying pulse duration time (0.02-3 sec) and energy density of electron beam. The results obtained are summerized as follows;
1) In most cases, a cavity is formed by electron beam.
2) At the initial time of welding, electron beam penetrates into metal at very high speed (about lm/sec, for instance, when electron beam of average energy density of about 5 × lO⁵ Watt/cm² is projected) and this speed depends largely upon energy density of electron beam.
3) In rest metal, penetration depth of welding continues to increase at a decreasing rate after the above initial step and that in moving metal it also increases in the same manner, but until a stationary state.
4) At the same time, penetration depth in moving metal is often superior to that in rest metal. This phenomenon is more considerable at lower energy density of electron beam.
Those results show that the movement of metal promotes the drilling action of electron beam because molten metal in moving metal is more easily pushed away to the cavity formed behind electron beam impinging point and electron beam can penetrates into deeper portion of metal.