What are ferrite magnets?

What are ferrite magnets?

Ferrite magnets are permanent magnets mainly made of SrO or BaO and Fe2O3. Compared with other permanent magnets, ferrite magnets are hard and brittle, and have lower magnetic energy. However, it is not easy to demagnetize and corrosion, the production process is simple and the price is low. Therefore, ferrite magnets have the highest output in the entire magnet industry and are widely used in industrial production.

Ferrite magnet is a sintered permanent magnet material composed of barium and strontium ferrite. In addition to strong anti-demagnetization performance, this type of magnet has the advantage of low cost. Ferrite magnets are hard and brittle, requiring special machining processes. The opposite magnet is oriented along the manufacturing direction and must be magnetized in the direction taken, while the same magnet can be magnetized in any direction because it has no orientation, although a slightly stronger magnetic induction is often found on the side where the pressure 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 and speakers to toys and handicrafts, so they are currently the most widely used permanent magnet materials.

Features of ferrite magnets

It is produced by powder metallurgy, with low remanence and low recovery permeability. The coercive force is large, and the anti-demagnetization ability is strong. It is especially suitable for the magnetic circuit structure used as 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. Working temperature: -40℃ to +200℃.
Ferrite magnets are divided into anisotropic (anisotropic) and isotropic (isotropic). Isotropic sintered ferrite permanent magnet materials have weak magnetic properties, but they can be magnetized in different directions of the magnet; anisotropic sintered ferrite permanent magnet materials have strong magnetic properties, but they can only be along the magnet Magnetize in a predetermined direction.

Physical properties of ferrite magnets

In the actual production of ferrite magnets, raw materials with good chemical composition sometimes may not be able to obtain ferrite magnets with good performance and microstructure. The reason is the influence of physical properties. The physical properties of iron oxide listed include average particle size APS, specific surface area SSA and bulk density BD. Since iron oxide accounts for about 70% of the manganese-zinc ferrite magnet formula, 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 the fact that the powder particles are too fine to be conducive to subsequent pressing and sintering, 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 spinel phase diffusion reaction can proceed, and the grain growth process cannot be further carried out. This will inevitably lead to an increase in the activation energy required during sintering, which is not conducive to solid-phase reactions.

Main performance grade parameters of sintered permanent ferrite magnet

Main performance grade parameters of bonded permanent ferrite magnet

The difference between ferrite magnet and neodymium iron boron magnet

Ferrite magnet is a metal oxide with ferromagnetism. In terms of electrical properties, the resistivity of ferrite is much larger than that of metal and alloy magnetic materials, and it also has higher dielectric properties. The magnetic properties of ferrite also show high permeability at high frequencies. Therefore, ferrite has become a non-metallic magnetic material widely used in the field of high frequency and weak current. It is a non-metallic magnetic material, which is a composite oxide (or ferrite) of magnetic ferric oxide and one or more other metal oxides. The magnetic force is usually 800-1000 Gauss, which is often used in speakers, speakers and other equipment.
The advantages of neodymium iron boron magnets are high cost performance and good mechanical properties; the shortcomings are that the Curie temperature is low, the temperature characteristics are poor, and they are easy to pulverize and corrode. They must be made by adjusting their chemical composition and adopting surface treatment methods. Improvements can meet the requirements of practical applications. NdFeB belongs to the third generation of rare earth permanent magnet materials. It has the characteristics of small size, light weight and strong magnetism. It is currently the magnet with the best performance-to-price ratio and is known as the magnet king in the field of magnetism. The advantages of high energy density make NdFeB permanent magnet materials widely used in modern industry and electronic technology. In the state of bare magnetism, the magnetic force can reach about 3500 Gauss.