What kind of steel balls are applied in bearings?

Chrome Alloy Steel Balls, the most common bearing alloy, are manufactured from steel of the hardening type AISI E-52100. The balls are heat treated to a hardness of 62 HRC minimum. They are strongly attracted by a magnet.

Hardened Stainless Steel Balls are widely used in bearings and valves, and are manufactured from steel AISI type 440C. Hardness is 58 HRC minimum. They are strongly attracted by a magnet.

Unhardened Stainless Steel Balls are manufactured from steel AISI Type 316 or 302. This material is only slightly magnetic. It may be machined, drilled, and tapped. It has the best corrosion resistance of the standard metals. Hardness is about 30 HRC.

Brass Balls are widely used in tooling and are manufactured from Copper 60-70%, Zinc 30-40%. They are easy to machine, drill, and tap. This material is nearly nonmagnetic. Hardness is 80 HRB.

Soft Mild Steel Balls are manufactured from steel, AISI type 1018. They are strongly attracted by a magnet. Soft mild steel is easy to machine, drill, and tap. The balls are highly polished for decorative applications etc. Hardness 28 HRC.

Aluminum Balls are manufactured from Aluminum Association Specification No. 2017 (SAE No.26). The material is nonmagnetic. It is easy to machine, drill, and tap.

Tungsten Carbide Balls are manufactured from high grade material in the range of Tungsten Carbide 93.5-94.5%, Cobalt 5.5-6.5%. The balls may be ground with diamond wheels and shaped with electro discharge machines. This is one of the hardest, toughest, and most rigid materials available. It is slightly magnetic.