Method and apparatus employing induction heating for welding plate edges, such as the plate edges of a seam cleft in a formed metal pipe blank

摘要

850,607. Electric induction heating. UNITED STATES STEEL CORPORATION. Aug. 9, 1957 [Aug. 17, 1956], No. 25243/57. Class 39(3). [Also in Group XXII] In preheating the spaced metal plate edges preparatory to welding therein, the edges are moved longitudinally, magnetic flux is induced on the edges generally parallel thereto and in opposite direction, in adjacent increments of the length thereof and magnetic return paths are provided for the flux outside of the edges, the induced eddy currents being confined to the increments in planes normal to the edges. A metal pipe blank 14 with spaced edges 13 travels under the preheating inductor P, Fig. 11, which comprises an elongated magnetic core 10, Fig. 9, with poles 11 around which a winding 12 is wound so that adjacent poles have opposite polarity . The winding is supplied with current at 1500-4000 e.g. 3000 cycles per second so that flux flows in the spaced edges from adjacent poles, the flux in adjacent increments of the length of the edges flowing in opposite directions. The blank preheated to 1300-1500‹F. passes under an inductor S, which induces flux across the edges and the edges are finally brought together by rolls 34. In an embodiment the core 10 of the preheating inductor is suspended by brackets 15 and two complete windings 12, each making one full turn about each pole, and confined between insulating plates 18, 19 spaced by posts 20. The windings formed from flat copper tube are connected at the right hand end to chambers 29 supplied with cooling water by pipes 30 and are connected at the left hand end to tubular conductors 31 extending from tubular bus-bars 32. Cooling pipes 23, 24 are arranged between the plates 18, 19 and the core and a thermal reflector sheet 26 of non-magnetic stainless steel is provided on the bottom of plate 19. The two windings are connected in series.