The method of grinding steel ball with grinding wheel in ball grinding machine after heat treatment is called hard grinding, its function is to eliminate the defects of soft grinding (or light grinding), remove the surface oxidation, decarburization, deformation and troostite structure defects generated in the heat treatment, and further improve the precision and surface quality.

In the process of steel ball hard grinding or after the end, the appearance should be checked for surface defects, after cold pickling check burns, burns can be generally divided into secondary tempering burns and secondary quenching burns, secondary tempering burns after cold pickling black, secondary quenching burns after cold pickling middle is gray martensite, surrounded by black troostite.There are linear burns, spot burns and bipolar burns (large ball burns).

Causes of linear burns:

1. The groove of cast iron disc or grinding wheel is too deep, which affects the rotation flexibility of steel ball;

2. The working face of cast iron disc or grinding wheel is not parallel or the groove depth is not consistent, resulting in the friction phenomenon of the steel ball on the top of the steel ball;

3. The groove of cast iron disc or grinding wheel does not match;

4. The junction between distributor and cast iron plate is not consistent;

5. The bell mouth at the inlet of the cast iron disc is too wide, so that the steel ball contacts the edge of the grinding wheel groove;

6. Improper adjustment of the gradient of the ball groove makes the steel ball flow too fast or too slow;

7. The grinding wheel drops a grain (block) to block the entry and exit of the ball;

8. The ball suction Angle of the ball collecting blade is flat or worn into a concave shape, and ball gathering is not smooth;

Improper application of work pressure.