Generally speaking, there are three ways to magnetize magnetic materials:
unsaturated magnetization, saturation magnetization, and supersaturation magnetization. Which method of magnetizing machine is used in which case is mainly determined by the requirements of the product. Generally, saturation magnetization is used more in engineering. 
1. Unsaturated magnetization:

It means that during magnetization, the energy cannot reach more than 95% of saturation magnetization. This magnetization is reversible, that is, with time and external force magnetic field changes, the remanence of the magnet will gradually decrease. This magnetization method only Used in special working occasions, the dosage is very small.
2, saturation magnetization:

It refers to the energy required for the magnetization energy to reach the inflection point of the magnetization characteristics of the magnetic material. It is generally 1.5 times (critical pull) -2 times of the intrinsic coercivity (or remanence) of the magnetic material, and generally 2 times for stability. This method can make the magnet saturated and magnetized, and demagnetization will not occur under normal circumstances.
3. Oversaturated magnetization:

It refers to the energy required for the magnetization energy to exceed the inflection point of the magnetization characteristics of the magnetic material. Generally, the intrinsic coercivity of the magnetic material is 3 times. Because of the characteristics of the magnetic material, the surface magnetic field of the magnet reaches saturation and increases with the external magnetization energy. Only minor changes. Therefore, this method is adopted in higher environments that require magnetic energy.