A device for inducing local heating in a sheet metal structure, by a method comprising the following method steps: a. providing a sheet metal structure comprising an area to be heated; b. providing a magneticfield generator; c. positioning the magnetic field generator adjacent to the sheet metal structure in the area to be treated such that it forms a resonance circuit arrangement together with the sheet metal structure; d. applying at least one calibration current pulse having a specific frequency to the resonance circuit arrangement in order to determine the resonance frequency of the resonance circuit arrangement; e. applying at least one power current pulse to the resonance circuit arrangement with the operation frequency of the current pulse corresponding to the resonance frequency of the resonance circuit arrangement as determined by the at least one calibration current pulse; wherein the device comprises: a. a power supply unit configured to provide an alternating current; b. a working head with the magneticfield generator for generating a magnetic field, the working head being electrically interconnected with the power supply unit; c. a power supply control unit to control operation of the power supply unit and adapted to perform steps d,e of the method; wherein d. the power supply unit and the working head are interconnect by means of a cable; wherein e. the working head comprises: i. at least one magnetic field generator for generating a magnetic field, comprising at least one electrical work coil; ii. at least one essentially U-shaped core, said U-shaped core comprising a first and a second leg (25, 26) and a yoke portion, the at least one electrical work coil being interconnected with the U-shaped core; iii. the first and the second leg (25, 26) each comprising a free end (27a,b) and a connecting end (28a,b), the connecting ends (28,a,b) being arranged at the yoke portion, wherein the distance between the free end of the first leg and the free end of the second leg is less than the distance between the connecting end of the first leg and the connecting end of the second leg; wherein iv. at least one capacitor (22a,b) is arranged in the working head, the capacitor (22a,b) being electrically interconnected with the work coil. a. providing a sheet metal structure comprising an area to be heated; b. providing a magneticfield generator; c. positioning the magnetic field generator adjacent to the sheet metal structure in the area to be treated such that it forms a resonance circuit arrangement together with the sheet metal structure; d. applying at least one calibration current pulse having a specific frequency to the resonance circuit arrangement in order to determine the resonance frequency of the resonance circuit arrangement; e. applying at least one power current pulse to the resonance circuit arrangement with the operation frequency of the current pulse corresponding to the resonance frequency of the resonance circuit arrangement as determined by the at least one calibration current pulse; a. a power supply unit configured to provide an alternating current; b. a working head with the magneticfield generator for generating a magnetic field, the working head being electrically interconnected with the power supply unit; c. a power supply control unit to control operation of the power supply unit and adapted to perform steps d,e of the method; wherein d. the power supply unit and the working head are interconnect by means of a cable; wherein e. the working head comprises: i. at least one magnetic field generator for generating a magnetic field, comprising at least one electrical work coil; ii. at least one essentially U-shaped core, said U-shaped core comprising a first and a second leg (25, 26) and a yoke portion, the at least one electrical work coil being interconnected with the U-shaped core; iii. the first and the second leg (25, 26) each comprising a free end (27a,b) and a connecting end (28a,b), the connecting ends (28,a,b) being arranged at the yoke portion, wherein the distance between the free end of the first leg and the free end of the second leg is less than the distance between the connecting end of the first leg and the connecting end of the second leg; wherein iv. at least one capacitor (22a,b) is arranged in the working head, the capacitor (22a,b) being electrically interconnected with the work coil. i. at least one magnetic field generator for generating a magnetic field, comprising at least one electrical work coil; ii. at least one essentially U-shaped core, said U-shaped core comprising a first and a second leg (25, 26) and a yoke portion, the at least one electrical work coil being interconnected with the U-shaped core; iii. the first and the second leg (25, 26) each comprising a free end (27a,b) and a connecting end (28a,b), the connecting ends (28,a,b) being arranged at the yoke portion, wherein the distance between the free end of the first leg and the free end of the second leg is less than the distance between the connecting end of the first leg and the connecting end of the second leg; wherein iv. at least one capacitor (22a,b) is arranged in the working head, the capacitor (22a,b) being electrically interconnected with the work coil.