Thixoforming of carbon steels: Inductive heating and process control

The development of steel grades for the production of thixoformed parts made a great progress but the process itself is still difficult to control. The most critical point is the inductive heating of the billets to assuring a homogeneous distribution of the desired liquid fraction. One of the principle approaches is based on investigations of the thermo-physical properties of steel grades. These data are also used for numerical simulation of the inductive heating. From these results a mathematical model is derived and implemented in the heating chain for controlling the parameters that determines the billet temperature indirectly by computation and not by direct measuring of the temperature. Optimizing the coil geometry leads to an adapted magnetic field assuring a homogenous temperature distribution in the billet considering expected energy losses. We will also present new results of the liquid fraction within the billet as well as the electrical resistivity of the thixotropic steel at high heating rate corresponding to the industrial scale. Last but not least, some new parts made out of adapted steel will be shown.