A.Diameter: 20~130mm B.Parameters of hot rolled steel ball: 1. The overall high hardness: surface hardness of 57-67 hrc, volume hardness of 56-64 hrc, and the hardness gradient distribute evenly. 2. High impact toughness: more than 12 j/cm2 3. Low broken rate: anti-broken and anti-broken off performance is 10 times of general casting steel ball, balls impact times over 20, 000 times, the actual broken rate is less then 1%, close to no broken.