The mainly raw material are 45# , B2  and  B3 steel rod.

The Cr & Mn contents are lower, not wear-resistant. If it used with B2 grinding ball, which has high hardness and wear resistance , the 45# steel ball will inevitably deform quickly and become smaller.

So some mine area choose B2 B3 material, B3 material Mn, Cr content is high, more wear-resistant, carbon content low, it not easy to break, higher hardness is more suitable for mining. The combination of the big ball of B3 and the small ball of B2 is perfect.