Reasons for the low hardness of shaft parts during high-frequency nga pagpalong:

① The power of the equipment is improperly selected, the heating specific power is small, and the heating time is short;

② The design of the inductor and cooler is unreasonable, and the inner diameter of the inductor is inconsistent with the workpiece, resulting in uneven heating and cooling;

③ The heating and cooling process is unreasonable, or there is water in the sensor, and it is attached to the workpiece to form a soft spot after quenching, or the pressure of the cooling medium is small, the flow of the medium is small, and the spray hole is blocked, resulting in insufficient cooling;

④ Excessive heating power and long heating time, overheating or coarse grains;

⑤ Coarse massive ferrite exists in the original structure, the carbon content of the material is too high or the hardenability of the material is too high or too poor;

⑥ Uneven tempering temperature or insufficient tempering;

⑦ The quenching temperature is low or the moving speed is too fast;