Volume 3, Issue 6 (June 2006)
Cleanliness of Bearing Steels and Fatigue Life of Rolling Contacts
Established metallographic methods of determining the cleanliness of bearing steels with respect to micro-inclusions, such as ASTM E 45, are capable of differentiating poor quality melts from good quality melts. However, as steelmaker capabilities improve, with increasing numbers being able to consistently produce good quality melts, the established methods of cleanliness assessment are unable to differentiate between melts. These established methods, which give single figure ratings based on both the size and number of inclusions, are extremely difficult to use in predicting the performance of a bearing component under conditions of rolling contact fatigue. In this work, the method of Extreme Value Analysis (EVA) is used to characterize the inclusion population of five different steel melts of known and varying quality. A link between the EVA distribution and the measured bearing life, performed on material with a low reduction ratio, is also presented.