A By available for direct heating of the metal workpiece, there is provided an apparatus for expanding the use range of Joule's law. Electrical / electronic device 1 for heating the A workpiece is adjustable power driver 2, the heating and the data acquisition controller 3 includes a power transformer 4, the adjustable power supply controller controls the heat treatment for the purpose of, possible adjustment through various setting parameters, which may be a three-phase and / or single phase, creating a voltage and frequency, heating and data acquisition controller 3, as a plurality of sensors 32 When configured input section, a processing unit, an output unit, a microprocessor device and a HMI, power transformer 4 has a particular characteristic, the secondary winding is different from the primary winding, cooling water is cooled through the extrusion cavity formed in the secondary core that flows through it. .FIELD 1