Method for induction surface hardening of a ring surface

A method for induction surface hardening a ring surface of a work piece by a hardening device having a primary heating inductor configured to heat the ring surface of the work piece from an initial zone to an end zone, a preheater inductor disposed upstream of the primary heating inductor in a direction of treatment and configured to preheat the ring surface of the work piece before the ring surface encounters the primary heating inductor, a sprayer disposed downstream of the primary heating inductor in a direction of treatment and configured to quench the heated work piece so as to harden the ring surface of the work piece from the initial zone to the end zone with an unhardened slip zone disposed between the initial zone and the end zone, the hardening device and the ring surface of the work piece being movable relative to one another in a direction of treatment when in a feeding mode, comprising:

• activating the preheater inductor, so as to preheat the ring surface of the work piece;
• setting a negative speed directly after the activation of the preheater inductor leading to a relative movement between the ring surface and the hardening device that is counter to the movement during the continuous hardening operation;
• setting a first speed v1 at which the hardening device and the work piece move relative to each other in a direction of treatment, so as to preheat locations on the ring surface moving past the preheater inductor;
• activating the primary heating inductor so as to increase the temperature of locations of the ring surface of the work piece moving past the primary heating inductor, and simultaneously setting a second speed v2 at which the hardening device and the work piece move relative to each other in a direction of treatment;
• activating the sprayer so as to apply quenching liquid to locations of the ring surface moving past the sprayer and quench the locations on the ring surface that have been heated by the primary heating inductor, and simultaneously setting a third speed v3 at which the hardening device and the work piece move relative to each other in a direction of treatment;
• deactivating the preheater inductor, and simultaneously setting a fourth speed v4 at which the hardening device and the work piece move relative to each other in a direction of treatment;
• and
• deactivating the primary heater inductor.