中頻感應加熱的原理：工件放到感應器內，感應器一般是輸入中頻或高頻交流電 (300-300000Hz或更高)的空心銅管。產生交變磁場在工件中產生出同頻率的感應電流，這種感應電流在工件的分布是不均勻的，在表面強，而在內部很弱，到內部接近于0，利用這個集膚效應，可使工件表面迅速加熱，在幾秒鐘內表面溫度上升到800-1000℃，但是內部溫度比較小

Principle of medium frequency induction heating: the workpiece is placed in the inductor, which is generally a hollow copper tube that inputs medium frequency or high frequency alternating current (300-300000Hz or higher). The alternating magnetic field generates the induction current of the same frequency in the workpiece. The distribution of this induction current in the workpiece is uneven. It is strong on the surface, but weak inside, and close to zero inside. With this skin effect, the workpiece surface can be heated rapidly. The surface temperature rises to 800-1000 ℃ within a few seconds, but the internal temperature is relatively small