In order to maximize the productivity of the induction heating device, the heating time should be as short as possible.

The process of metal induction heating can be regarded as two stages:

1) The metal in the range of current penetration depth is heated directly by the flowing current;

2) The metal in the central part of the blank outside the current penetration depth is heated by heat conduction from the surface layer.

To reduce the heating time, we should mainly rely on shortening the heating time of the inner layer - the heating of this layer depends on the heat transfer from the surface layer, which will increase the temperature difference between the blank core and the surface. This temperature difference is not allowed to exceed a certain value. The following specifications are usually used as the limit for increasing the heating speed - that is, at the end of heating, that is, when the surface layer reaches the forging temperature, the temperature of the blank center is 100 ℃ lower than that of the surface layer. This specification first determines the induction heating time of the blank.