Abstract: An induction heating apparatus of a plate-like member for arranging a plate-like member having a three-dimensional structure so that it is interposed between a pair of plate-like coils and inductively heating the plate-like member, the pair of plate-like coils having a three-dimensional structure that corresponds to the plate-like member and being arranged to be opposed to each other. The plate-like member arranged between the pair of plate-like coils includes a plurality of surfaces in a predetermined cross section perpendicular to a current that flows through the plate-like coil pair, and each of the coils of the plate-like coil pair is divided into a plurality of turns along the direction in which the current flows for at least each of the plurality of surfaces of the plate-like member.

Abstract: A heating method capable of changing thermal hysteresis for each part of the center pillar for the vehicle is provided. A heating method includes heating, when the center pillar for the vehicle is annealed, the center pillar by induction heating so that: a strength of a part of the first part other than the flange part becomes higher than that of the flange part of the first part, and the strength of the flange part of the first part becomes higher than that of the second part; and toughness of the second part becomes higher than that of the flange part of the first part, and the toughness of the flange part of the first part becomes higher than that of the part of the first part other than the flange part.

Abstract: A hot-press molding method of the present disclosure includes a first heating process in which a steel plate is heated and the entire steel plate becomes austenite, a first cooling process in which a cooling rate of the steel plate after the first heating process is partially changed, a first region which is a part of the steel plate is transformed into martensite, and a second region other than the first region remains as austenite, a second heating process in which the entire steel plate is reheated and the first region becomes tempered martensite, and a second cooling process in which the entire steel plate after the second heating process is cooled. At least one of the first cooling process and the second cooling process is performed during a molding process in which the steel plate is press-molded on a molding die.

Abstract: An induction heating apparatus of a plate-like member for arranging a plate-like member having a three-dimensional structure so that it is interposed between a pair of plate-like coils and inductively heating the plate-like member, the pair of plate-like coils having a three-dimensional structure that corresponds to the plate-like member and being arranged to be opposed to each other. The plate-like member arranged between the pair of plate-like coils includes a plurality of surfaces in a predetermined cross section perpendicular to a current that flows through the plate-like coil pair, and each of the coils of the plate-like coil pair is divided into a plurality of turns along the direction in which the current flows for at least each of the plurality of surfaces of the plate-like member.

Abstract: A heating method capable of changing thermal hysteresis for each part of the center pillar for the vehicle is provided. A heating method includes heating, when the center pillar for the vehicle is annealed, the center pillar by induction heating so that: a strength of a part of the first part other than the flange part becomes higher than that of the flange part of the first part, and the strength of the flange part of the first part becomes higher than that of the second part; and toughness of the second part becomes higher than that of the flange part of the first part, and the toughness of the flange part of the first part becomes higher than that of the part of the first part other than the flange part.

Abstract: A method of producing a steel plate member including: quenching a steel plate by heating a steel plate to a temperature which is higher than a first transformation temperature at which austenitization is completed, and then cooling the steel plate at a cooling rate higher than an upper critical cooling rate; reheating a second area of the steel plate, without reheating a first area of the steel plate, to a temperature which is higher than a second transformation temperature, at which austenitization starts, and is lower than the first transformation temperature; and cooling the steel plate at a cooling rate lower than a lower critical cooling rate.

Abstract: A hot-press molding method of the present disclosure includes a first heating process in which a steel plate is heated and the entire steel plate becomes austenite, a first cooling process in which a cooling rate of the steel plate after the first heating process is partially changed, a first region which is a part of the steel plate is transformed into martensite, and a second region other than the first region remains as austenite, a second heating process in which the entire steel plate is reheated and the first region becomes tempered martensite, and a second cooling process in which the entire steel plate after the second heating process is cooled. At least one of the first cooling process and the second cooling process is performed during a molding process in which the steel plate is press-molded on a molding die.