Induction hardening for large bearing rings: case study and process optimization

Induction quenching can be used for hardening the outer surface of large bearing rings, achieving superior mechanical properties, with the advantage that heating is not required for the whole part. The benefits of applying this technique compared to conventional heat treatments are twofold: firstly, the energy consumption is reduced, and secondly the productivity is increased, due to the significantly lower processing period.

The desired goal is to obtain a hardened layer on the active surface of the bearing ring, uniform in both section and circumference, having a predetermined thickness. After the induction hardening process, on a limited number of specimens, the following problems could be observed: uneven depth of the hardened layer in different areas along the ring circumference, uneven depth of the hardened layer reported in the ring section, and cracks in the bearing material.

The main objective of the optimization process is to pinpoint the specific parameters involved in the bearing rings quenching operation, which can lead to the aforementioned defects. Consequently, the technological conditions that lead to the appearance of defects have been ranked; heating/cooling processes simulations have been performed, leading to the proposal of new inductors geometries, which take into account new product configurations/section geometries.