Induction Hardening of Steering Pinions: High-Speed Process – High Component Quality

The standardization of production is a trend in automotive engineering as uniformly designed, perfectly configured production plans guarantee highly efficient practices at different sites. The production process is tailored to different components – a trend which naturally also affects mechanical engineering, since “off-the-rack” solutions cannot meet this demand. The example of the induction hardening of steering pinions clearly shows the system concepts machine manufacturers are developing to react to this and EMAG subsidiary eldec offers customized systems to integrate hardening into the production flow.

Millions of steering pinions are produced every year by large supply companies. This component is used in all steering systems and ensures that the steering force is transferred to the steering gear and then ultimately to the wheels – a process that happens millions of times over the life cycle of a car. This means that the strength of these components, and the material used to produce them, has the very highest priority, making hardening processes essential. However, hardening components produced in large scale manufacturing processes often presents a logistical challenge. Many suppliers have the process completed by a third party in the form of case hardening, requiring a heat treatment specialist, creating additional costs and planning work.  

Hardening in under one second
eldec technology delivers a whole host of benefits in this respect. This EMAG subsidiary is a global player with headquarters in Germany which develops, manufactures and sells highly efficient induction heating technology for a very wide range of industrial applications. The technological alternative to case hardening is not only faster and more energy efficient, but eldec systems can be integrated perfectly in series production systems where they become integral components of complete production lines. Making this a viable option is the speed of the process. While a steering pinion must be heated over a period of hours for case hardening, the induction process takes less than one second with the heat applied by the induction of eddy currents. This method only heats the parts of the component to be hardened – a small area on the surface with a depth of just a few millimeters. “This is a basic requirement for the incredible speed of the system,” explains Stefan Rechtacek, a member of the Technical Sales team at eldec. “We control the frequency at which the eddy currents are applied with extreme perfection."

SDF technology improves component quality
The benefits of a special eldec innovation are particularly clear when processing steering pinions – generators featuring simultaneous dual frequency (SDF) which supply the energy for the hardening machines. With SDF, two different frequencies are applied to the workpiece. While mid-frequencies generally penetrate more deeply and, above all, heat the foot of the tooth, high frequencies heat the head of the tooth. The heating process on the steering pinion using SDF therefore achieves absolutely uniform depth and temperature levels. This ensures a standard hardening finish even on large modules. “We tailor the required energy source perfectly to the component. There are no standard solutions. That is why we have an extremely flexible concept for our generators,” adds Rechtacek.   

Hardening technology from a single source
The same also applies to the eldec module induction (MIND) series of hardening machines, also perfectly tailored to the workpiece dimensions, required hardening finish and batch size. Only time-tested components are used thanks to the company’s modular element system. This benefits the stability of the systems and also means that the technology offers proven value for the investment. Finally, made with micrometer precision based on the workpiece using 3-D CAD software, the production of the inductor tools also meets the customer’s specifications. “We supply our customers with a tailored machine which includes robot automation systems, if necessary. They can be integrated perfectly in production lines with soft and subsequent hard machining processes as a complete hardening system,” explains Rechtacek.  Steering pinion production from the raw part to the finished component can then be carried out in a multi-stage process which may also feature grinding and turning machines from EMAG. Automotive customers are supplied with a complete turnkey solution.

Focusing on machining quality
Finally, the guaranteed machining quality and true to size properties of the MIND Series lends it to the large scale production of this safety-relevant component. The expansion of the steering pinion using eldec technology is a maximum of just 0.2 millimeters. This is an extremely low value for hardening, and one which can be reproduced at any time – a major factor for the establishment of new production plants in Asia or South America. “We are often approached by companies that require extraordinary machining quality for their components. We can guarantee that reproducibility. We also supply custom systems for extremely low cost hardening processes. These benefits mean that we are enjoying ever greater success on the market,” concludes Rechtacek.