The basic principle of high frequency
Put the workpiece into the inductor (coil). When an alternating current of a certain frequency is passed into the inductor, an alternating magnetic field is generated around it. The electromagnetic induction effect of the alternating magnetic field causes a closed induction current-eddy current in the workpiece. The distribution of induced current on the workpiece cross-section is very uneven. The current density on the surface of the workpiece is very high and gradually decreases inward. This phenomenon is called the skin effect. The electrical energy of the high-density current on the surface of the workpiece is converted into thermal energy, so that the temperature of the surface is increased, that is, the surface is heated. The higher the current frequency, the greater the difference in current density between the surface and the interior of the workpiece, and the thinner the heating layer. After the temperature of the heating layer exceeds the critical point temperature of the steel, it is rapidly cooled to achieve surface quenching.