GB566866A - Improved method of and apparatus for heat treating metal - Google Patents

Abstract

566,866. Electric induction heating. RADIO CORPORATION OF AMERICA. April 30, 1943, No. 6881. Convention date, April 30, 1942. [Class 39 (iii)] A strip of steel 1 is inductively heated by a coil 3 having a part 3a which sets up a highfrequency field along the longitudinal direction of the strip, thereby heating the strip by hysteresis losses, and a part 3b which sets up a field at right angles to the first, thereby continuing the heating of the strip by eddy current losses after the hysteresis loss has become zero at a temperature of about 1300‹ F. Each of the parts 3a, 3b may consist of one or more turns of metal tube through which a cooling fluid circulates. In Fig. 4, the coil consists of a strip of sheet material bent to a single loop which encloses the strip 1. The two ends 19 are connected to the supply, and at the opposite end of the diameter of the coil an opening 15 is formed, from which a slit 17 extends to one edge. The passage of current around the coil and around the opening 15 sets up the two fields at right angles. In Fig. 6, steel strip 1 is fed from a reel 21 through guide 25 to heating coil 3 as described above, then through a water-cooled quench block 27, then through a coil 29 similar to 3a which heats it to a lower tempering temperature, and finally through a quench block 31. In modifications, the coils 3a, 3b may be separate and may be connected to the same or different sources, or a simple solenoid may be arranged at an angle to the strip 1 to provide the component fields.