In-depth Induction Heating of Large Steel Slabs exploiting Magnetic Saturation: Modeling and Results

In induction heating about 87% of the power is generated within the penetration depth. In case of magnetic steel below the Curie Temperature due to the high magnetic permeability the penetration depth is in the order of 5-6 mm at 50 Hz. A surface heating is then obtained if large steel slabs (with a typical thickness of 200-300 mm) are processed. The penetration depth can be increased if the material is brought to saturation by applying an external DC magnetic field and a faster in-depth heating can be obtained. The saturating field can be produced with no losses over large volumes by means of present state of the art superconducting coils. The induction heating of large steel slabs is numerical investigated in this paper. A model is developed to solve numerically the coupled eddy current-magnetostatic-thermal problems by using the same space discretization. Actual dependence of the physical properties of the material on the temperature and flux density is implemented. Heating power and temperature profiles are calculated for some cases of practical interest. Self and mutual inductance of the inducting AC coil and the saturating DC coil are also evaluated in order to be used for the system design.