Rapid Evaluation of Inclusions in Bearing Steel

The rolling contact fatigue (rcf) life of bearing steel is closely related to the steel cleanliness. To assess steel cleanliness, traditional methods such as optical image analysis and Statistics of Extreme Value are often used. The results obtained using these traditional methods of assessing steel cleanliness correlate well with the rcf life. More recently, pulse height distribution analysis (PDA) has been developed to determine steel cleanliness. Despite some issues surrounding the PDA method for assessing steel cleanliness, PDA is still considered to be superior to traditional methods for the quick assessment of nonmetallic inclusion in steels. A comparison has been made between the steel cleanliness results obtained by traditional optical image analysis and PDA to determine if the results of PDA can be used as a meaningful indicator of the rcf life of bearing steels. The comparison showed that the size of inclusions obtained by PDA agreed reasonably with the size of inclusion obtained using optical image analysis. Consequently, it should be possible to use the PDA results as an indicator of rcf life.