Q: The mechanism of polishing steel balls for bearings.
A: 1. The grinding effect of polishing plates.
The grinding effect of polishing plates is related to the internal metallographic structure of polishing plates and the external process conditions during processing.
In the state of use, the main metallographic structures of polishing plates 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 brittle, and becomes 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 light grinding process, the graphite and hard and brittle abrasive particles on the surface of the plate groove are constantly broken and shed, and the circulating flushing of the cleaning liquid causes the surface of the plate groove to continuously produce and reveal new sharp edges, thus maintaining the continuous grinding ability of the light grinding plate.
In summary, the grinding effect of the light grinding 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 the cleaning liquid.
2. The form of metal shedding on the steel ball surface.
During the light grinding process, the small sharp edges raised on the plate groove surface can vertically cut into the ball surface under pressure, and the tangential force causes the sharp edges and the ball surface to move relative to each other. As a result, the steel ball surface is sheared, plowed or cut, causing metal wear and shedding, leaving visible fine groove marks on the steel ball surface. Therefore, the shedding of metal on the steel ball surface belongs to abrasive wear, and the grinding of the steel ball surface by the light grinding plate can be regarded as a fixed metal abrasive grinding.
