The inductive heating of the feedstock material is a very important step in the processing of semi solid metals. On the one hand, the billet has to be heated as fast as possible to the target temperature. On the other hand, it must be guaranteed that the outer area does not begin to melt prematurely. Also, at the end of the heating the billet should have an uniform temperature distribution in order to obtain good forming results. A flatness based control will be presented to calculate the induced power over time trajectory from a desired trajectory for the temperature in the middle of the billet. The temperature trajectory has to be chosen so that the billet has the desired temperature behaviour. Experimental results will be shown for the flatness based inductive heating of X210CrW12 just below the semi solid state.