GB748528A - Improvements in tube welding - Google Patents

Abstract

748,528. Welding by pressure. MAGNETIC HEATING CORPORATION. Dec. 22, 1953 [Jan. 21, 1953], No. 35615/53. Class 83 (4). [Also in Group XI] In welding the edges of a longitudinal gap in a metal tube, the tube is advanced longitudinally and pressure is applied to close the gap at the welding point, the gap edges being heated by applying a high frequency current of at least 10,000 cycles per second to the tube by electrodes which engage the tube on or near the gap edges and such that the greater part of the current flows along the edges, which form the lowest impedance path between the electrodes, to the welding point. The tubing is fed to rollers 13, 14 where the gap 11 is closed and welding effected at point 12. Current at frequency of 10,000-500,000 cycles per second is supplied to a block 21 carrying a contact 15 in sliding contact with one of the gap edges and flows along the one edge of the gap to the point 12 and along the other edge to a contact 16 insulated from contact 15. Current flows from contact 16 along a hollow hair-pin conductor 30 extending close to the edges of the gap and then to a block 22a. The current in the conductor 30 flows in opposite direction to that in the gap edges and reduces the inductance of the path along the edges. Additional insulated rollers 25, 26 may be used to ensure good contact with the contacts 15, 16. A cooling fluid is circulated through the blocks and through the hair-pin conductor. The contacts may be offset, contact either the inner or outer tube surfaces or be provided by rollers.