Nearly ten years have passed since the LF-RH-CC process was adopted in the production of bearing steels. This process has become a common system for steelmakers, regardless of using EFs or BOFs as melting furnaces. The current cleanliness level of bearing steels shows a remarkable improvement when compared to that of ten years ago. The oxygen content in most steels has reached the high level of cleanliness of less than 10 ppm throughout the world. The bearing life in laboratory tests has been extended by several times in the last ten years.
However, in the fields of engineering and technology of bearing production and applications, it is still a matter of primary concern how to settle the problems of inside and outside debris— that is, how to grasp quantitatively and control accurately nonmetallic inclusions in steels and how to deal with outside debris that penetrates into the bearings exposed to application environments. This paper presents the latest results of studies relating to these timely problems.