Current concentrator for highfrequency seam welding

982,337. Welding by pressure. OHIO CRANKSHAFT CO. Nov. 9, 1962 [Nov. 22, 1961], No. 42511/62. Heading B3R. [Also in Division H5] Apparatus, for continuously seam welding a pipe 20 having spaced longitudinal edges 22, 24 converging into a welding point 26 and defining a split 28, comprises means for advancing the pipe along a predetermined path, means 30, 32 for moving the edges 22, 24 into abutting engagement at the welding point 26, power means for causing a high frequency current X to flow along the edges 22, 24 and across the welding point 26, and a highly electrically conductive non-magnetic insert 40 for concentrating the high-frequency current along the edges 22, 24 and across the welding point 26, the insert 40 being spaced from the power means and extending into the split 28 and between the edges 22, 24. In the arrangement shown, the insert 40 is supported by bolts 49, and the current X is induced into the pipe by a hollow water-cooled C-shaped inductor 18. Alternatively the current X may be supplied to the pipe by brushes on opposite sides of the welding point 26. In each arrangement, high-frequency current Y induced into the insert 40 concentrates the current X in the required regions. The insert 40 may be water-cooled and may be insulated from the edges 22, 24. A modified insert (Fig. .4, not shown) has flanges which extend over the edges 22, 24.