In rolling bearings, the sliding tracks of the rolling elements must be hardened. In bearings with a double row of rolling elements, in particular with a double row of balls used in vehicle hub bearing units, induction hardening of the rolling tracks of the outer ring of the bearing is a particularly delicate operation. In fact, the presence of sharp edges between the two adjacent tracks implies risk of over-heating and cracking; on the other hand, if the heating power is decreased to avoid these risks, there is the risk of not achieving a hardening profile that is suitable in depth, extension or surface hardness of the hardened area.
Moreover, the induction heating devices, or more simply, inductors currently used, are bulky, difficult to construct and/or maintain and sometimes with a not entirely satisfactory reliability.