The most widely used steel grade for rolling bearings is based on a steel composition first used almost a hundred years ago, the so-called lC-1.5Cr steel. This steel is used either in a selective surface induction hardened condition or in a through hardened heat treated condition, both yielding exceptional structural and contact fatigue properties. The Lundberg and Palmgren rolling bearing life prediction model, published in 1947, was the first analytical approach to bearing performance prediction, subsequently becoming a widely accepted basis for rolling bearing life calculations. At that time the fatigue life of rolling bearings was dominated by the classical sub-surface initiated failure mode. This mode results from the accumulation of micro-plastic strain at the depth of maximum Hertzian stress and is accelerated by the stress concentrations occurring at the micro internal defects. In common with all fatigue processes, rolling bearing failure is a statistical process: the failures of bearings with high inclusion content tested at high stress levels belong to the well-known family of "Weibull" distributions. Steady improvements in bearing steel cleanliness due, amongst other things, to the introduction of secondary metallurgy steel making techniques, have resulted in a significantly increased rolling bearing life and load carrying capacity. In recognition of this, in 1985 Ioannides and Harris introduced a new fatigue life model for rolling bearings, comprising a more widely applicable approach to the modelling of bearing life based on the relevant failure mode. Subsequently this has been extended to include effects of hardness and of micro-inclusion distributions in state-of-the-art clean bearing steel.

Proceedings of the May 1998 symposium on steel, stainless steel, and related alloys. Emphasizing the effect on the products rather than manufacturing methods, seven papers show that the level of inclusion identification and control through processing improvements is greatly dependent upon the sector

The rolling contact fatigue testing of low oxygen, high quality, rolling bearing steels is a major challenge to steel makers, bearing producers and end users. Material specimen based rolling contact fatigue tests were used for a number of years, mainly as acceptance tests. Often in this type of test, the applied contact stress exceeds the stress normally found in rolling bearing applications and also exceeds the limit stress for rapid cyclic micro-plastic groove formation in the rolling contact. For these reasons the established methods have limited ability to discriminate material quality effects in modern high cleanliness rolling bearing materials. Furthermore, the results of tests based on a material specimen are difficult to translate into life calculation factors for the bearings. In this paper a novel test method is presented and used to determine the effect of steel internal cleanliness on the performance of rolling bearings. To achieve this result considerable care is required in the preparation of the test elements, the selection of the specific test conditions and in the analysis of the results. This work also led to an ability to determine the dependence of steel quality on the steel making processes. Material cleanliness is characterized using the statistics of extreme values of the micro-inclusion size population allowing the steel cleanliness quality rating to be related directly to the fatigue performance of rolling bearings through the introduction of a material cleanliness factor ?. The expected bearing life performance for materials with different inclusion size ratings can thus be calculated. Results correlate well with measurements demonstrating that the quality rating of the material can now be reliably included in standard bearing life calculations.

One of the main causes of in-service spalling of bearing steels is fatigue crack initiation from non-metallic inclusions. At the present time, while the relationship between endurance and cleanliness of bearing steels is obvious, no quantitative relationship between them has been established. The aim of this paper is to present a new quantitative method which predicts the rolling fatigue life distribution of bearings. This approach is based on a model of fatigue crack initiation in the vicinity of an inclusion in the steel matrix and on a simple fatigue crack propagation relationship. This basic model is used in a statistical approach to describe the scatter of fatigue lives using the distribution of inclusions in the Hertzian zone. The fairly good agreement with fatigue results shows that this approach constitutes a real future tool for predicting the influence of the main material parameters on the fatigue life distribution of bearings.

This handbook shows how to prevent bearing failure, how to avoid replacement and down-time costs, and how to solve bearing failure problems quickly when they do occur - avoiding delayed orders and lost business. No other handbook covers such a wide range of bearing types and seals, shafts and housing, materials and manufacture. There is no other troubleshooting guide to help technicians and mechanics monitor, mount and dismount, and lubricate correctly. Rolling Bearings Handbook and Troubleshooting Guide puts the right maintenance and diagnostic procedures at your fingertips.