Abstract: A narrow gap arc welding process comprises steps of defining a narrow gap between a pair of members to be welded arranged so as to face each other at a predetermined distance, feeding a consumable electrode into a guide cylinder which is movable along the narrow gap, and generating electric arc between the tip of the consumable electrode and the members to be welded to unite them with each other, wherein the consumable electrode, while being deformed plastically to have a wave-like pattern with a pitch of about 10 to 30 mm and a molding width of about 2 to 5 mm depending on welding conditions, is fed into the narrow gap with the direction of the molding width being in line with the direction of the width of the narrow gap and the direction of the tip of the consumable electrode being changed so as to point out one after the other facing edge of the members to be welded alternately at a high frequency. Also, an apparatus for practicing the process is described.

Abstract: An electron beam working apparatus for cylindrical workpieces having a circular working line is improved so that a volume of a vacuum chamber to be maintained can be minimized and the vacuum chamber may not contain a contamination source such as a driving motor. In order to achieve the improvements, two disk-shaped partition plates having inflatable annular seal members disposed along their respective outer peripheral surfaces are placed inside the cylindrical workpieces respectively above and below the working line with said seal members pressed against the inner peripheral surfaces of said cylindrical workpieces to form a first vacuum chamber surrounded by said two partition plates and the inner peripheral surfaces of said cylindrical workpieces.