GB510648A - Improvements in or relating to method of and apparatus for electrical resistance welding of a longitudinal seam in tubing - Google Patents

Abstract

510,648. Electric heating. SESSIONS, F. L. Sept. 28, 1938, No. 28214. [Class 39 (iii)][Also in Group XXII] In electric resistance butt or flash welding the longitudinal seam of a tube by moving the tube progressively between a pair of contact electrodes, such as rollers, connected to a source of impulsive welding current, and engaging opposite sides of the seam, the flow of current from the electrodes around the back of the tube is reduced or prevented by inducing an opposing E.M.F. on the back of the tube. This may be effected by placing a magnetic core in the tube in the vicinity of the electrodes or internal and external cores. One or both cores may carry separably energized electric coils. In the form shown in Figs. 7-9 internal and external cores 6a, 7a are provided. In Fig 25, a longitudinally adjustable bar 44 is secured to a bar 45 on which is mounted the internal magnetic core 6a. Secured to the bed opposite the core is an external core 7f. The internal core carries a two part coil 8c, 8d, the first coil 8c being provided with conductors 74, 75 and the rear coil with conductors 76, 77. The welding electrodes may be connected to a transformer supplied from an auto transformer in one of the phases of a three phase supply. An adjustable auto transformer connected to a second phase is connected to the coils via a reversing switch, variable inductance and condenser, so as to vary the voltage, reactance, and phase relation of the current supplied to the coils. When a two part coil is used the coils may be connected by switches so that they may be arranged in parallel or in series.