Simulation is a good choice to find the best frequency to heat the step properly.
The Surface Impedance approach enables simulation of high frequency induction heating in few minutes, without building a huge mesh. Induced heat in a steel strip is accurately calculated in 10 minutes for 300 kHz, while traditional FEM simulation takes about 10 hours.
Heating of the 10 cm 45 teeth gear up to the austenitization temperature performed with overnight simulation, taking into account changes of magnetic properties over Curie temperature. You can get hardening profile without cutting the gear and optimise frequency within in a couple of days.
1h simulation allows to test performance of a new-designed coil virtually, saving time and money for building it.