**6. Conclusion**

52 Heat Treatment – Conventional and Novel Applications

• possibility to set initial stretch more reliably

• running smooth even in the first hours of operation

**Figure 9.** Measuring ovality using the Talyrond 73 measuring device

Table 8. The material corresponds to the prescribed values.

**Table 8.** Chemical composition of 100Cr6 bearing material in % by weight

• lower noise of the equipment when these bearings are used

• lower operating temperature even when running the equipment in

• slight increase in dynamic load (due to optimised shape of ring and tapered roll

Extract from a chemical composition protocol - chemical analysis of 100Cr6 used is shown in

**Tested element Prescribed values Measured values** C 0,9 – 1,1 1,02 Mn 0,3 – 0,5 0,35 Si 0,15 – 0,35 0,28 Cr 1,3 – 1,65 1,51 P max. 0,027 0,01 S max. 0,03 0,014 Ni max. 0,30 0,06 Cu max. 0,25 0,09 Ni+Cu max. 0,5 0,15

Extract from a metallographic analysis protocol under DIN 17230, DIN 50602, SEP 1520, and corporate standard is shown in Table 9. The material corresponds to the prescribed values.

• reduced friction and tear and wear

• minimum run-in time

raceways)

The herein described method of achieving lower internal tensions with effect on reduced deformations and ring ovality made it possible to attain ovality of finished rings of 0.003 mm compared to the standard requirements on ovality of 0.006 mm. This result was achieved with a satisfactory assessment of chemical, metrological and metallographic analysis with a further effect on improved endurance of bearings. This manufacturing method has been tested several times since then and the desired effect was confirmed. Subsequently, this procedure has been applied also to other types of the so-called thin-walled bearings for others customers, in particular from the automotive industry, who demanded stricter ovality values. The possibility to use this technology has been confirmed in all cases.

Note: Compliance with and check of prescribed processing condition are essential for heat treatment. An appropriate way how to improve checks during the heat treatment is to use a computer-controlled hardening line. Obviously, this incurs higher input costs. According to information from the company where this optimised method of heat treatment was implemented, the system started to be used for a typical hardening line and the benefit in terms of quality exceeded their expectations.
