Erfahrungen mit Einzel-Gasabschreckung von Ringen aus durchhärtendem Wälzlagerstahl

The manufacturing costs of rings made of through-hardening bearing steel strongly depend on the distortion after hardening, as they determine the grinding costs. For rings sensitive to distortion the application of so-called fixtures in oil is commonly used, as long as it is reasonable from an economical point of view. With this method especially the dimensional variations of the rings are suppressed by using external clamping forces. This method is relatively expensive, as special fixturing tools are necessary for nearly every ring type. On the other hand for batch gas quenching the required cooling rate can only be achieved with gases like hydrogen or helium and high gas pressures. Next to that a uniform cooling rate within one ring and from ring to ring cannot be guaranteed. One solution is offered by the application of single-piece gas quenching in a nozzle field. There the high thermal energy transfer of an impinging flow is utilized, which is very uniform along the circumference of the ring as long as the shape of the nozzle field is adjusted properly. This publication reports on the first experiences with single-piece station gas quenching of rings made of through-hardening bearing steel.