The hardness value of the surface of the grinding medium steel ball can increase to some extent with time, but after a certain time, the hardness increase is not obvious and the time is long, the production efficiency is low, and the crack and damage of the ball surface are easy to occur. The difference between the ball and the ball is very poor. Therefore, it is necessary to limit the strengthening time, and under the premise of ensuring the hardness, the inner pole difference and the spherical aberration are minimized, and the metallographic structure and crushing load of the steel ball are in an optimal state.
At the beginning of the strengthening of the grinding medium steel ball, the hardness of the surface of the steel ball will increase rapidly, and the hardness of the surface of the steel ball will increase rapidly at the beginning of the strengthening stage. The uniformity of the ball and the spherical aberration of the uniformity generally rose, reaching a peak at about 2 to 4 hours; then began to fall, and the lowest point appeared at about 4 to 6 hours.
The influence of the strengthening time of the grinding medium steel ball on the metallographic structure, after the heat treatment, the internal metallographic structure is martensite and retained austenite. Martensite has dislocation type and twin crystal type. The dislocation type is lath-like, very uneven. It can be uniform after strengthening. The twin crystal form is flake-shaped, very brittle, and it is broken after strengthening, which will induce cracks. The production.