Q: The polishing mechanism of steel balls for bearings.

A: 1. The grinding effect of the polishing plate.

The grinding effect of the polishing plate is related to the internal metallographic structure of the polishing plate and the external process conditions during processing.

In the state of use, the main metallographic structures of the polishing plate are martensite, carbide and graphite. Martensite and carbide are both hard and brittle phases; while the strength and hardness of graphite are close to zero, and it is like a hole in the plate,cutting the matrix and causing stress concentration.

When the steel ball moves along the plate groove under a certain pressure, it moves relative to the surface of the plate groove. Due to the effects of dislocation and impact, the graphite and hard and brittle matrix on the surface of the plate groove quickly break and fall off, forming many small pits, uneven, and the raised irregular parts are mainly martensite, which is both hard and brittle2, forming a large number of small sharp edges. When the steel ball moves relative to the plate groove, under the action of pressure, these raised sharp edges grind away the metal on the surface of the steel ball like the abrasive grains of a grinding wheel.

During the polishing process, the graphite and hard and brittle abrasive grains on the plate groove surface are constantly broken and shed, and the circulating flushing of the cleaning fluid causes new sharp edges to be continuously generated and exposed on the plate groove surface, thus maintaining the continuous grinding ability of the polishing plate.

In summary, the grinding effect of the polishing plate depends on the metallographic structure inside the plate on the one hand, and on the other hand, there must be appropriate external process conditions: a certain pressure, relative movement between the ball and the plate groove, and continuous washing with cleaning fluid. 2. The form of metal shedding on the surface of the steel ball. During the polishing process, the small sharp edges raised on the surface of the plate groove can cut into the ball surface vertically under the action of pressure, and the tangential force causes the sharp edges and the ball surface to move relative to each other. As a result, the surface of the steel ball is sheared, plowed or cut, causing metal wear and shedding, leaving visible fine groove marks on the surface of the steel ball. Therefore, the shedding of metal on the surface of the steel ball belongs to abrasive wear, and the grinding of the steel ball surface by the polishing plate can be regarded as a fixed metal abrasive grinding.