Cleanliness assessment: a critical review and a real need to predict rolling contact fatigue behaviour

摘要

The refinement of secondary steelmaking processes allows the steelmakers to produce very low oxygen and sulfur bearing steel grades. As it was pointed out many times previously, the specifications in terms of the O and S contents and ASTM rating constitute a necessity but are not sufficient to guarantee good contact fatigue properties. As for hard mateirals like bearing steels, the fatigue endurance is directly a function of internal defects such as nonmetallic inclusions (nmi), a lot of investigations have been conducted during the last years in order to develop methods which can describe as accurately as possible the dist ribution of nmi in the steel matrix. While each method provides specific information concerning the nmi, further work is currently in progress to combine the results obtained from several methods to further improve the accuracy of the prediction of rolling contact fatigue behaviour. In the present paper an approach developed through our previous research work is described.