In the ferrite magnetic field molding process, wet press molding is to directly place the slurry after the secondary ball milling in the mold, and apply a certain direction (consistent with the direction of the magnetic field required when the product is used) during press molding. The magnetic field causes the easy magnetization axis of the single domain crystal grains to be aligned along the direction of the external magnetic field. At the same time, the water must be pumped out when pressing, and the upper and lower punches need gaskets to prevent the slurry from being drawn out, and then dry after molding. Because of the high water content in the slurry, the wet-pressing molding process allows the crystal grains to rotate freely during the molding process, which facilitates the orientation of the crystal grains, so that the magnetic properties are good and the Br is large and the Hcb is high. However, gaskets and suction filtration are required during molding, which results in low production efficiency. Dry press molding is to add a proper amount of binder (Binder) to the dry powder without moisture after secondary ball milling, and place it in a molding magnetic field for compression molding. The magnetic field orientation of dry pressing is slightly worse, and the magnetic properties are worse than that of wet pressing.
The production process of Sintered Ferrite is usually to mix the raw materials according to the composition ratio and then pre-fire (about 1300°C) into a crude permanent magnet product. The pre-fired crude product has poor performance and unstable performance. It needs to be ball-milled again into a powder below the single domain size, molded under a sufficiently strong external magnetic field, and finally sintered in a short time (1200°C~1280°C).
