Through-hardening grades
We specialize in high-strength through-hardening bearing steels. To harden steel, the iron matrix must contain a certain amount of carbon. The higher the carbon content in the steel the higher achievable hardness. In through-hardening steel, there is a relatively high level of carbon added to the steel – around 0.7% by weight. Chromium is also added as a key alloying element for hardenability and wear resistance. When the component is heat treated, it becomes hard all the way through from the surface to the core, hence the term “through-hardened”.
These grades exhibit high fatigue and wear resistance, good machinability, high hardness and good dimensional stability. A hardness of 60-65 HRC can be achieved through martensitic hardening and tempering, making these steels ideal for bearing products.
One of our most popular through-hardening grades is 100Cr6 (SAE 52100). This is a true bearing steel intended for rolling contact and other high fatigue applications. In the hardened condition, its high hardness, high strength and high cleanness provides the steel with the right properties to withstand high cycle, high stress fatigue. 100Cr6 is mainly used for small and medium sized bearing components. It is also regularly used for other machine components that require high tensile strength and high hardness.
Case-hardening grades
The other main category of steels used by manufacturers of transmission systems is case-hardening steel. In case hardening, the finished component is exposed to a carburizing (carbon-rich) furnace atmosphere at a high temperature, typically 850–950°C. This increases the carbon content at the surface of the component. The carburized layer is typically 0,5–1,0 mm deep but can be deeper. Following carburization, the part is quenched to harden it.
During quenching the carburized layer is transformed to martensite with a hardness determined by the carbon content – which is typically 0.10-0.25%. The result is a component with a hard surface and a comparably soft and therefore tough core. Typical components made from case-hardening steel are gears, shafts and camshafts in transmissions.
Ovako’s case-hardening bearing steels have been developed to offer good machinability and minimal dimensional change after hardening. A grade in common use with bearing manufacturers is 20NiCrMo2-2 that is designed to provide tough core properties and a hard surface for use in gears and shafts, but not directly for bearing applications.
A fully integrated bearing steel supplier
Ovako has the capability to supply a broad range of steel solutions to meet the specific needs of bearing manufacturers. Furthermore, we go well beyond supplying steel to operate as a fully integrated bearing steel producer. That means we control the whole production chain, from melting the steel through rolling to producing a finished component.
Our product ranges of tube, bar, ring and wire accommodate all the main components of a rolling bearing. And for the most demanding applications, our families of BQ-Steel® and IQ-Steel® are trusted solutions that meet the highest levels of cleanness to optimize fatigue strength and predictable product performance.
