Patent GB-869336-A (GB)
Title: Improvements relating to high-frequency seam welding
IPC: B23K13/04
Filed: 1958-08-29
Abstract: 869,336. Making saws; welding by pressure. MAGNETIC HEATING CORPORATION. Aug. 29, 1958 [Aug. 29, 1957], No. 30058/60. Divided out of 833,588. Addition to 851,530. Classes 83 (2) and 83 (4). In welding together opposed edges of elongated metal portions having different heating pattern requirements and/or welding temperatures, the portions are advanced so that their opposed edges travel past a welding point in the region of which the edges are retained firmly together, electric current having a frequency not less than 100 kilocycles per second is applied conductively to the portions to flow therein along paths in or adjacent the edges in advance of the welding point to heat the edges to welding temperature and an impedance pattern is established in the portions at least substantially complementary the required heating pattern by positioning an element of magnetic material of high volume resistivity adjacent to each portion, the elements being of different size and/or distance from the welding point. In an embodiment a strip HC, Fig. 1, of high carbon steel is advanced together with a strip HS of high speed steel with a V-shaped gap between them to a weld point w where rollers 11, 12 force the edges together. Fluidcooled contacts 20, 21 are applied at or adjacent the edges of the strips and are supplied with current of frequency up to 300,000 or 450,000 cycles per second, the current following the edges to and from the weld point. Current concentrating blocks 52 of magnetic material of high volume resistivity and of different sizes and/or distances from the welding point, only one being shown in Fig. 1, are mounted for vertical and longitudinal adjustment adjacent the edges. The edges are preheated to say 1000‹ F. by a cooled induction coil 14 supplied with current at a frequency of several thousand to above. 10,000 cycles per second and in addition the contacts 20, 21 may be spaced at different distances from the weld point. In a modification the contacts 25, 26, Fig. 2, are arranged to provide current flowing in the same direction in the edges, the contact 25 having flanges engaging the edges on the underside and the contact 26 engaging the edges on the upper side at or near the weld point which may be beyond the first point of contact of the edges. Current flows also in conductor 31 just above the gap to concentrate the currents. The blocks of magnetic material 35, 36 of different sizes are spaced above each edge and the edges are preheated as before. A large portion of the welded strip HS welded to strip HC along line 60 is slit off along the dotted line 62, Fig. 4, and teeth 63 are cut on the edge of the strip HC to produce a hand saw blade with teeth having speed steel tips. A high carbon steel strip may be welded on each side of a narrow high-speed steel strip and the latter is slit along the median line to provide material for two composite blades. The edges of the portions, bevelled as in Fig. 7, to predetermine the position of the weld upset on one side or the other as in Fig. 8. Specifications 748,528, 772,398, 851,528 and 869,337 also are referred to.