A ball mill, after the heat treatment of steel ball from hard grinding wheel for grinding method is called, its role is to eliminate the soft grinding mill (or light) defects, remove heat treatment of surface oxidation and decarburization, deformation and troostite tissue defects, further improve the precision and surface quality.
Second, in the process of steel ball grinding hard or ended, should carry on the appearance inspection surface defects, cold pickling check after burns, burns, generally can be divided into secondary burn tempering and second quenching burns, secondary tempering burns after cold pickling show black, secondary hardening burns martensite after cold pickling for middle gray, is surrounded by black troostite.It presents linear burns, point burns, and bipolar burns (large ball burns).
Causes of linear burn:
1. The cast iron plate or grinding wheel groove is too deep, affecting the rotation flexibility of the steel ball;
2. The working face of cast iron plate or grinding wheel is not parallel or the groove is not consistent, resulting in the friction phenomenon of steel ball top steel ball;
3. The groove of cast iron disk or grinding wheel does not match;
4. The distributor does not agree with the junction of the cast iron plate;
5. The mouth of the iron plate is too wide, so that the steel ball contact the edge of the grinding wheel groove;
6. Improper adjustment of the groove of the flow trough makes the ball flow too fast or too slow;
7. The grain (block) of the grinding wheel is blocked, so that the incoming and outgoing ball is not smooth;
8. The ball suction corner of the ball cutter is flat or worn into a concave shape, and the ball is not smooth;
Improper work pressure.
Causes of point burns:
1. The grinding wheel speed is too fast and the steel ball suddenly accelerates;
2. When the grinding wheel drops (block) on the surface of the ball, the local pressure increases sharply;
3. The grinding wheel groove crack or the defect of the falling block hit the steel ball;
4. The main shaft bearing of machine tool is damaged, so that the grinding wheel is too large;
5. The cast iron plate has the sand hole, the stoma and the hard grain, so that the surface of the ball surface is too much pressure;
6. The distributor does not agree with the junction of the inlet of the cast iron plate, or the splitter stops the ball at the entrance, and is injured by the groove of the grinding wheel;
7. Goal channeling at the entrance of cast iron plate;
8. The goal is too slow, too few steel balls between the grinding wheel and the plate, and the ball pressure is too great;
9. The coolant is too dirty and the grinding wheel is not cleaned in time.
Causes of bipolar burn:
1. Some dead angles on the machine tool make the individual ball not get the normal grinding surface to be a big ball, the big ball is only in the groove, and the rotation is not caused by the friction between the two grooves of the grinding wheel;
2. When a groove is blocked by grinding wheel block and material first class, it is not detected and excluded in time. After a long time, the ditch will become shallow, and when the ball is re-entered into the groove, there will be two pole burns.
Dry run steel ball in each process is very strict in accordance with the production process and process, pay attention to each small step, can produce a higher precision miniature steel ball