Internal Welding of Stainless-steel Tubes

Abstract

PRELIMINARY experiments have recently been performed to investigate a novel method of welding together cylindrical non-magnetic stainless steel tubes, using an electric arc. The two tubes to be joined were spigoted together, and an arc was struck between the interface of the tubes and a concentric internal electrode. By means of a magnetic field applied transverse to the axis of the arc it was possible to keep the arc roots in continuous motion¹ on the central electrode and at the join of the tubes. If a suitable choice of electrode geometry and polarity, arc current and gas atmosphere were made, those parts of the tubes adjacent to the internal electrode could be brought to a red- and then white-heat, following which welding occurred. Since the complete cylindrical region adjacent to the join was uniformly heated there was little danger of introducing thermal stresses, and where necessary the arc could be run at reduced current, following welding, so that the welded section cooled less rapidly, and was partly annealed.