A major advance in high-power electron-beam welding in air

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Abstract
A major extension of the capabilities of nonvacuum electron-beam welding follows from the development of a machine with higher beam power. Tests with a new atmospheric electron gun operating at 60 kW have shown that the advantages of nonvacuum electron-beam welding must be reevaluated. Gas heating produced by the beam itself becomes very pronounced, so that electron scattering is reduced causing the high-power density of the beam to be retained over larger working distances. Single-pass butt welds with a depth-to-width ratio of 4 : 1 can be made in 3.8-cm-thick steel at a speed of 0.77 cm/sec, while the ultimate welding depth exceeds 5 cm. Medium thick material, e.g., 1.3-cm steel, can be welded at a 5-cm work distance, with a depth-to-width ratio of 3 : 1. The large work distance permits access to more complex structures and interior corners such at T sections, which can now be fabricated from a plate, 1.3 cm thick, at a speed of 2–3 cm/sec, making a full through weld from one side. Also, seam welds of two 3-mm-thick hot-rolled steel sheets can be produced at speeds of up to 15 cm/sec. High-power machines need not be significantly larger or costlier than low-power guns, and the present 60 kW does not represent any technical limit. Welding efficiency improves with higher power; when welding steel of 2 cm thickness or more the energy efficiency of the process at 60 kW is better than 50%, while at 40 kW it is merely 30%. In addition, the high power permits greater welding speed. These developments translate directly into improved cost justification for electron-beam welding and a broad expansion of its possible applications.

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