METHOD FOR PRODUCING GRINDING BALLS Russian patent published in 2021 - IPC C21D9/36 C21D1/00 B21H1/14 

FIELD: rolling.

SUBSTANCE: invention relates to rolling and heat treatment of grinding balls made of steel containing, wt%: C - 0.71-0.75; Mn - 0.90-1.00; Si - 0.25-0.35; Al - less than 0.010; P - less than 0.015; S - less than 0.010; Cr - 0.40-0.45; Ni - 0.10-0.14; Cu - less than 0.020; V - 0.08-0.12; Mo - less than 0.010; Ti - less than 0.015; H - less than 0.0003; iron is the rest. The method includes rolling the balls or heating the balls at a temperature of 950-1050°C. After that the balls are cooled to a temperature of 750-820°C. Then it’s necessary to quench the balls in a quenching medium. The balls are tempered. The duration of quenching is regulated depending on the diameter of the balls. The balls of a nominal diameter of 15-35 mm should be quenched from 1.0 to 2.0 min. The balls of a nominal diameter of 40-50 mm should be quenched from 1.5 to 3.0 min. The balls of a nominal diameter of 60-80 mm should be quenched from 2.5 to 3.5 min. The subsequent tempering of the balls is carried out with a holding time from 140 to 280 minutes. The balls with a nominal diameter of 15-35 mm are tempered at a temperature of 150-190°C, and the balls with a nominal diameter of 40-80 mm are tempered at a temperature of 160-220°C.

EFFECT: invention is aimed at increasing the operational durability of balls, obtaining grinding balls with a volumetric hardness characterized by hardness group 5 according to GOST 7524-2015 on a production scale.

3 cl, 2 tbl, 1 ex