Basic knowledge of hard grinding of bearing steel balls

- Oct 19, 2020-

Steel ball processing technology: after heat treatment, the hard grinding steel ball of the bearing steel ball is ground with a grinding wheel on the ball grinding machine. The method is called hard grinding. Its function is to eliminate soft grinding (or smooth grinding) defects and remove surface oxidation, Decarburization, deformation and troostite structure defects further improve accuracy and surface quality. During or after the hard grinding process of the steel ball, the surface defects should be visually inspected, and the burns should be inspected after cold pickling. The burns can generally be divided into secondary tempering burns and secondary quenching burns. The secondary tempering burns appear black after cold pickling. After the secondary quenching burn is cold pickled, the middle is gray martensite, and the surrounding is black troostite. There are linear burns, spot burns and bipolar burns (large ball burns).

Causes of bipolar burns:

1. Some dead corners on the machine tool prevent individual balls from getting the normal grinding surface and become large balls. The large balls revolve in the groove and do not rotate and are squeezed by the friction between the two groove edges of the grinding wheel;

2. A certain groove is blocked by foreign matter such as grinding wheel block, material head, etc., and if not detected and removed in time, the groove will become shallow over time. When the ball re-enters the groove, bipolar burns may occur.