Hard Ferrite Sintered Permanent Magnets

Ferrite oxide magnets, also known as ceramic magnet or hard ferrooxide, ferrooxide magnets as non-metallic permanent magnet materials, using iron oxide (Fe2O3), barium carbonate (BaCO3) or strontium carbonate (SrCO3) as raw materials, therefore, ferrooxide magnets can be divided into strontium ferrooxide magnet and barium ferrooxide magnets by composition.Strontium ferroferrite magnets and barium ferrite magnets are also called anisotropic ferrooxide magnets and isotropic ferrooxide magnets, respectively.In addition to their superior cost advantages and corrosion resistance, the ferrooxide magnets are moderately magnetic and can be applied at relatively high temperature conditions.

As permanent magnets made of oxides, sintered ferrite magnets such as hexagonal magnetoplumbite type (m type) sr ferrite or ba ferrite are known (refer to Japanese Patent Laid-Open No. 2001-57305 ). ). As indexes for evaluating the magnetic properties of permanent magnets, residual magnetic flux density (br) and coercive force (hcj) are generally used.

How are ferrites manufactured and what are the production processes

1. Weighing and mixing

Ferrite raw materials include main raw materials, additives and fluxes Fe2O3, BaCO3, SrCO3 and CaCO3 are the main raw materials of ferrite. The weighing process needs to strictly follow the formula, otherwise the ideal magnetic properties cannot be obtained. After the raw materials are weighed, they are mixed in special equipment. Ingredient uniformity is based on the mixing process. There are many factors that affect the uniformity of a mixture's components.

2. Granulation

In order to ensure the smooth progress of the solid phase reaction process, the mixture needs to be granulated before pre-sintering. During the granulation process, the solution will be sprayed into the mixture. The particle size of the pellet material has an effect on the burn-in time.

3. Pre-sintering

The purpose of pre-sintering is to fully ensure the solid-phase reaction of the raw materials. After pre-sintering, most of the raw materials will be converted into ferrite phase. The pre-sintering process will also improve deformation, shrinkage and density. The pre-sintered powder can be used as a raw material for sintered magnets, bonded magnets and wave absorbing materials. Now most ferrite manufacturers directly purchase the pre-sintered powder.

4. Ball mill

In this step, the pre-sintered material will be pulverized into a fine powder. The crushing process will be completed by the ball mill equipment. The grinding medium is steel balls and water.

5. Forming

On the basis of traditional classification methods, ferrite magnets are divided into two categories: isotropic and anisotropic. Ferrite molding methods are also divided into two types: wet method and dry method. The molding process is highly technically intensive.

6. Sintering

Like other types of sintered magnets, the sintering step is also very important for ferrite magnets. First, the sintering process affects the microstructure of the ferrite, which in turn affects the magnetic properties of the ferrite. Unreasonable sintering parameters can lead to cracks in the magnet. , bubbles and deformations.

7. Machining

Processing methods of ferrite magnets include grinding, polishing, cutting and punching. It is worth mentioning that because ferrite is an insulating material, magnet manufacturers will use grinding wheels during the cutting step.