They are steels for the rings and rolling bodies that use balls and rollers to maintain the separation between the moving parts of the bearing.
The following types of bearing steels are differentiated (alloyed with one or more of the following elements): hardened throughout their mass (Cr, Mo); hardened by case-hardening (Cr, Mo, Ni), hardened by induction (Cr, Mo); stainless (Cr, Mo, Ni, V, N); of high temperature (Cr, Mo, Ni, V, W).
Their most common applications are for ball or roller bearings, woodworking tools, lathe spindle centers, reamers, dies and grinding of hard and very abrasive materials.