APPARATUS FOR INDUCTION HEATING AT THE SIDE EDGE PART OF GRAIN-ORIENTED SILICON STEEL SHEET

PURPOSE:To prevent the generation of buckling strain at the edge part in either side of a steel sheet in contact with a receiving base in finish annealing, by executing control in such a manner that the edge part in either side in the breadth direction of the steel sheet is heated to an optimum temp. in a pre-stage of finish annealing for a grain-oriented silicon steel sheet. CONSTITUTION:In a pre-stage of finish annealing for a strip S, an induction heating apparatus 1 provided with a C type iron core 1a and a coil 1b is installed, and an edge part (s) in either side in the breadwise direction of the strip S is allowed to enter into the gap 1c of the C type iron core 1a by a prescribed length. By this constitution, power is supplied to the coil 1b to subject only the edge part (s) in either side, and the variation in the heating temp. is detected by a sheet temp. detecting element. In accordance with the above detected variation, an electric current flowing into the coil 1b is decided by a controlling apparatus 3, and a prescribed voltage is impressed via an inverter 4. In this way, the edge part (s) in either side is heated to an optimum temp. to enlarge crystalline grains and to increase its strength, by which, at the time of coiling the strip S into a coil and executing finish annealing, the generation of buckling strain at the edge part (s) in either side in contact with a receiving base is prevented, and the magnetic properties of the product is also kept good.