How we increase the hardness of our slewing bearings

A slewing bearing from the upper side

How we increase the hardness of our slewing bearings

While fossil fuels are becoming increasingly scarce, the demand for energy is growing worldwide. Limited resources and rising energy prices are global challenges and an inspiration for our experts at thyssenkrupp rothe erde to create innovative solutions. As resilient components, slewing bearings and rings in wind turbines, hydroelectric and tidal power plants and solar energy systems make a significant and sustainable contribution to global resource conservation and climate protection.
To make large-diameter bearings particularly resistant to their use amid the forces of nature and to prepare them for all axial and radial forces acting on them, our experts have developed a special process to increase the hardness of the bearing rings. The patent “Method for the production of a bearing ring for large-size rolling bearings” with the file number PCT/EP2006/001266 describes how a bearing ring is heated in the electric field of an inductor during its manufacturing and then cooled – thus obtaining a high degree of hardness over its entire surface.

While earlier processes already used two counter-rotating inductors for hardening bearing rings, that were moved over the bearing ring in the feed process, they reheated an already hardened area when the inductors met again. The result: a so-called slip – a small segment that is incompletely hardened due to the process and where the bearing ring remains softer.

The solution from thyssenkrupp experts: In an automated process, at least two induction coils uniformly heat the bearing ring to hardening temperature. In addition to the two coils, a third induction coil is provided which, through swinging movements, ensures a uniform heating zone and constant heating depth in the slip area. Moving sprinklers attached to the two induction coils can then cool the material evenly.

Through these coordinated movements, the process achieves a uniform and common heating surface. Coordinated cooling prevents slippage.