With the new Cronitect® material, Schaeffler Group Industrial (INA/FAG) presents the result of ongoing development of high-performance stainless steels. Cronitect® rolling bearings can operate under extreme conditions, for instance when in contact with corrosive media such as water, acids, cleaning agents, or even under dry operation – and they are available in both sealed and non-sealed versions.
During the past years, the call for bearings suited to applications under extreme conditions has risen significantly. The demand for media-lubricated or even dry-running bearings especially has strongly advanced the development of new technical solutions. This development is driven by necessities such as tighter legal requirements, for example in the food industry, increased awareness of a sustainable use of resources and environmental protection as well as the pursuit of energy-efficient, robust solutions.
The reduction or complete abandonment of lubricants is one possible approach that makes the use of complex sealing systems unnecessary.
Media lubrication and dry operation require extremely high mechanical, chemical and thermal resistance of the bearings. The main parameters for meeting these demands are the micro and macro geometries as well as the material combinations of the various bearing components. Here the Schaeffler Group offers a wide range of corrosion resistant and cycling resistant types of steel and coatings. The new Cronitect® material is the result of the ongoing development of high-performance stainless steels. Cronitect® is a martensitic hardening steel that achieves a very high hardness and supreme corrosion resistance through its chemical composition in combination with a new thermochemical surface layer treatment process. For example, Cronitect® shows no signs of corrosion even after 600 hours of salt spray testing in accordance with DIN 50021 SS. Thus its corrosion resistance is far better than that of conventional stainless steels. Table 1 shows the most essential differences between Cronitect® and standard stainless steels as well as the classic rolling bearing steel 100Cr6.
Its extreme corrosion resistance, suitability for dry operation and long service life under conditions of mixed friction make Cronitect® an interesting option for applications in nearly all industrial sectors. Examples are packaging and food processing technology, materials handling technology, productronics, transmission engineering, heavy machinery, fluid & air handling and consumer products. Cronitect® can be used for the whole range of bearing solutions, from conventional rolling bearings of all types and designs to linear guides and classic plain bearing supports.
Two basic configurations can be realized with classic rolling bearings: When combining Cronitect® bearing rings with ceramic rolling elements in unsealed rolling bearings, the rolling contact runs dry or is “lubricated” by the surrounding medium. The second variant combines conventional stainless steels such as AISI440C for the rolling elements with Cronitect® rings and bearing seals. In this configuration, the main focus is on extended life under insufficient lubrication and on emergency operating features.
The use of Cronitect® bearings in food processing technology significantly increases the availability of machinery and permits extended maintenance intervals. For example, in bottling plants it used to be necessary to replace all bearings (material AISI440C) affected by cleaning detergents every four months. Thanks to Cronitect®, this interval can be now doubled. In the field of sports and fitness equipment, rolling bearings must withstand corrosive environments, for instance in fishing reels or in bicycles. The main focus with fitness equipment is on friction minimization in order to improve the smooth running properties. The use of Cronitect® eliminates the need for grease lubrication as well as for complex and high-friction seals. This again requires a high degree of corrosion resistance, the basic suitability for dry operation and high wear resistance. Cronitect® meets all three of these demands at once.
