The demand for rolling bearings that are able to withstand extreme operating conditions is on the increase, including dry-running and media-lubricated bearings. This demand is being fuelled by tighter legal requirements in many industries, an increased awareness of scarce resources and the need for companies to become more energy-efficient.
The Schaeffler Group has launched a high performance stainless steel for rolling bearings that helps companies achieve these goals. Cronitect provides maximum corrosion resistance under extreme operating conditions, including dry running applications or when bearings come into contact with aggressive media such as water, salt spray, acids and cleaning chemicals.
Cronitect steel is a high-grade martensitic hardening steel that is based on the consistent refinement of high-grade NIROSteels. Through its unique composition and new thermo-chemical surface layer treatment process, Cronitect achieves an extremely high hardness. Even after 600 hours of salt spray testing in accordance with DIN 50021 SS, the material shows no signs of corrosion.
The name Cronitect is derived from the chemical composition of the material (chromium and nitrogen alloying elements) and from its special heat treatment process. The “tect” suffix is found in other Schaeffler coating products and refers to the material's excellent corrosion protection. Cronitect's resistance to corrosion is many times better than that of conventional NIROSteels.
The heat treatment process optimises the surface zone and core properties of the base material. This produces a hard, wear-resistant surface zone with very high corrosion-resistance and a tough core.
Cronitect is suitable for a wide range of industrial applications, including food and beverage processing, materials handling, heavy machinery (e.g. gear pumps, flow dividers), power transmission systems (gearboxes), hydraulic and pneumatic systems, consumer products and packaging.
In the food industry, the demand for dry running bearings is increasing. Cronitect can be used across most of Schaeffler's product range, including rolling bearings, linear guides and plain bearings.
Rolling bearings that use Cronitect are available in both sealed and non-sealed versions. When used in conjunction with ceramic rolling elements, Cronitect bearings are particularly suitable for dry running operation.
The second version combines conventional stainless steels such as AISI440C for the rolling elements with Cronitect rings and bearing seals. In this configuration, the focus is on extended life under insufficient lubrication and on emergency operating features.
In food processing, the use of Cronitect significantly increases the availability of machinery, providing extended maintenance intervals. For example, bottling plants typically would normally have to replace all their AISI440C rolling bearings that come into contact with cleaning detergents, every four months. With Cronitect bearings, this interval can now be doubled.
Rolling bearings and linear guides are already using Cronitect for a wide range of applications in the food industry, including meat processing, filling plants, packaging machines, fish processing and poultry production.
In a recent cam control solution for a bottle capping machine company, Schaeffler replaced its original solution – a standard stud type track roller immersed in an oil bath – with a roller stud, Cronitect outer ring, corrosion-resistant steel balls and an HRS seal.
The new solution requires no lubricating oil, has extremely high resistance to corrosion and aggressive media, while presenting no risk of contamination of foodstuffs. This has resulted in improved hygiene, reduced maintenance costs and higher machine availability.
In sports and fitness equipment, rolling bearings must provide excellent corrosion resistance, for example, in fishing reels, inline roller skates, cycle fitness machines, sailing equipment and for the wheel hub bearing supports on racing cycles. On fitness machines, friction has to be minimised to ensure smooth running properties. Here, the use of Cronitect eliminates the need for grease lubrication and complex, high friction seals.
