The ferrite magnet is a sintered permanent magnet material, which is composed of barium and strontium iron. In addition to strong anti-demagnetization performance, this magnetic material has the advantage of low cost. Ferrite magnets are hard and brittle, and require special machining processes. Because the opposite-sex magnets are oriented along the manufacturing direction, they must be magnetized in the direction taken, while the same-sex magnets can be magnetized in any direction because they are not oriented, although a slightly stronger magnetic induction is often found on the side where the pressure-receiving surface is the smallest. The magnetic energy product ranges from 1.1MGOe to 4.0MGOe. Due to its low cost, ferrite magnets have a wide range of applications, from motors, speakers to toys and handicrafts, so they are currently the most widely used permanent magnet materials.
1. Features
It is produced by powder metallurgy, with low remanence and low recovery magnetic permeability. The coercive force is large and the anti-demagnetization ability is strong, which is especially suitable for the magnetic circuit structure used in dynamic working conditions. The material is hard and brittle and can be used for cutting with emery tools. The main raw material is oxide, so it is not easy to corrode. Operating temperature: -40°C to +200°C.
Ferrite magnets are divided into anisotropy (anisotropy) and isotropy (isotropy). The magnetic properties of isotropic sintered ferrite permanent magnet materials are weak, but they can be magnetized in different directions of the magnet; anisotropic sintered ferrite permanent magnet materials have strong magnetic properties, but only along the direction of the magnet Magnetize in a predetermined magnetization direction.
2. Physical properties
In the actual production of ferrite magnets, raw materials with good chemical composition may not always be able to obtain ferrite magnets with good performance and microstructure. The reason is the influence of physical properties. The listed physical properties of iron oxide include average particle size APS, specific surface area SSA and bulk density BD. Since iron oxide accounts for about 70% in the formula of manganese-zinc ferrite magnet, its APS value has a great influence on the APS value of ferrite magnet powder. Generally speaking, the APS value of iron oxide is small, and the APS value of ferrite magnet powder is also small, which is beneficial to speed up the chemical reaction. However, considering that the powder particles are too fine, it is not conducive to the subsequent pressing and sintering, and the APS value should not be too small. Obviously, when the APS value of iron oxide is too large, during pre-sintering, due to the large particle size, only the diffusion reaction of the spinel phase can be carried out, and the grain growth process cannot be further carried out. This inevitably leads to an increase in the activation energy required for sintering, which is not conducive to the solid-phase reaction.
