Induction hardening of large bearing rings is a very challenging procedure due to the complex physical processes and their interactions, which need to be properly controlled to produce components meeting the imposed requirements of e.g. wind turbines. The different process parameters significantly alter the resulting microstructures and properties of such a bearing ring. The evolution of numerical simulations in the last decades allows the modelling of processes with a growing complexity. In this work, the challenges of a simulation model for induction surface hardening are shown and discussed. Besides the theoretical background of the interacting physical fields and a brief note about available software packages, the paper focusses on the elaboration of a necessary material database and on the specific problems of induction scan hardening processes for large bearing rings.