| CPC B21D 37/16 (2013.01) [B21D 19/08 (2013.01); B21D 28/02 (2013.01)] | 10 Claims |

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1. A processing method comprising:
punching a steel plate to open a part of an end surface of the steel plate to form an open trim edge;
disposing a heating coil in a non-contact manner along the end surface of the open trim edge formed in the punching to sandwich the end surface of the open trim edge therebetween, so that the heating coil is disposed on a first side of the end surface of the open trim edge and on a second side of the end surface of the open trim edge; and
heating the end surface of the open trim edge by applying an alternating current to the heating coil to generate an induced electromotive force on the steel plate, wherein
a current direction of the heating coil that is disposed on the first side of the end surface of the open trim edge is opposite to a current direction of the heating coil that is disposed on the second side of the end surface of the open trim edge.
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