Steels, and in particular bearing steel technologies, have gone through profound developments and some of these are reviewed in this book. Improved metallurgical cleanliness and a requirement for improved composition consistency have necessitated developments in both air-melt and remelt steelmaking. Carbon steels, through hardening, surface hardening and highly alloyed corrosion resistant high-speed steels are used in rolling bearings. Compositions are specified together with the development history of the standard 52100 bearing steel. The virtue in the 52100 (1C-1.5Cr) steel composition is described and information given as to why it is still used more than a century after its introduction. Case carburization bearing steel technologies are widely used in line contact rolling bearings and the development is described. The developments in the use of selective surface hardening in angular contact automotive wheel ball bearings is introduced. Air-melt steelmaking, casting and rolling and remelt steelmaking such as vacuum induction melting, electroslag remelting and vacuum arc remelting are reviewed for special requirements such as precision aerospace. Clean-steel powder metallurgy in combination with hot isostatic pressing is introduced as an upgrade to the properties of high alloy steels with hot-hardness characteristics. Knowledge of rolling bearing loading and the appropriate metallurgical design is fundamental to bearing steel technologies. Bearing steels are only suitable for rolling bearing manufacture once appropriate soft forming, prior soft treatments, subsequent final hardening heat treatments and damage-free hard machining have been applied. Different rolling bearing types can require different steel technologies and damage, failure terms and characteristics are reviewed. Accurate failure characterization, metallurgical and functional property testing are key topics. Metallurgical quality testing with respect to macro-, meso-, and microinclusion testing is reviewed and developments continue. Rolling contact fatigue and substitute fatigue testing methodologies have become difficult as bearing steels have improved and this is covered in detail later in the book.
