Rare earth permanent magnet materials
Rare earth permanent magnet materials (NdFeB Nd2Fe14B) are divided into the following three types according to different production processes:
(1) Bonded NdFeB
Bonded NdFeB is a composite NdFeB permanent magnet made by uniformly mixing NdFeB powder with resin, plastic or binder such as low melting point metal, and then compressing, extruding or injection molding. The product is formed once, and can be directly made into various complex shapes without secondary processing. Bonding NdFeB is magnetic in all directions and can be processed into NdFeB compression molds and injection molds. High precision, excellent magnetic properties, good corrosion resistance and good temperature stability.
(2) Sintered NdFeB
Sintered NdFeB permanent magnet is smelted after being milled by airflow, with high coercivity value and extremely high magnetic properties, and its maximum magnetic energy product (BHmax) is more than 10 times higher than that of ferrite (Ferrite). Its own mechanical properties are also quite good, and it can cut different shapes and drill holes. The maximum operating temperature of the high-performance product can reach 200°C.
Due to its material content that can easily lead to rust, different layers must be applied to the surface according to different requirements. (such as zinc plating, nickel, environmental zinc, environmental nickel, nickel copper nickel, environmental protection nickel copper nickel, etc.). Very hard and brittle, with high anti-demagnetization, high cost/performance ratio, not suitable for high operating temperatures (>200°C).
(3) Injection NdFeB (Zhusu NdFeB)
It has extremely high accuracy and is easy to make thin-walled rings or thin magnets with complex anisotropic shapes.
Sintered ferrite
The main raw materials of sintered ferrite (Sintered Ferrite) include BaFe12019 and SrFe12019, which are divided into isotropic and anisotropic magnets according to the orientation of the magnetic crystal.
Because of its low price and moderate magnetic properties, it has become a widely used magnet. Ferrite magnet is manufactured by ceramic process, the texture is also relatively hard, but also a brittle material, because ferrite magnet has good temperature resistance and low price, has become a more widely used permanent magnet.
Rubber magnetic
Rubber Magnet is one of the ferrite magnetic material series, which is made of bonded ferrite powder and synthetic rubber composite by extrusion molding, calendering molding, injection molding and other processes to make magnets with flexibility, elasticity and twistability. It can be processed into strips, rolls, sheets and various complex shapes. Rubber magnets are composed of magnetic powder (SrO6Fe2O3), polyethylene (CPE) and other additives (EBSO, DOP), etc., and are manufactured by extrusion and calendering. Rubber magnets can be homogeneous or heterogeneous, it is made of ferrite magnetic powder, CPE and certain trace elements, bendable, twistable and rollable. It can be used without more machining, and the shape can also be trimmed according to the required size, and the rubber magnet can also be combined with PVC, adhesive backing, UV oil, etc. according to customer requirements. It has a magnetic energy product between 0.60 and 1.50 MGOe. Application areas of rubber magnets: refrigerators, information billboards, fasteners that fix objects to metal bodies for advertising, etc., magnetic sheets for toys, teaching instruments, switches and sensors. Mainly used in micro motors, refrigerators, disinfection cabinets, kitchen cabinets, toys, stationery, advertising and other industries.
Alnico
Alnico (AlNiCo) is the first permanent magnet material developed, which is an alloy composed of aluminum, nickel, cobalt, iron and other trace metal elements. According to the different production processes, it is divided into sintered Alnico (Sintered AlNiCo) and cast Alnico (Cast AlNiCo). The shape of the product is mostly round and square. The casting process can be processed into different sizes and shapes; Compared with the casting process, sintered products are limited to small sizes, and the blank size tolerances produced by them are better than those of cast products, and the magnetic properties are slightly lower than that of cast products, but the machinability is better. Among the permanent magnet materials, cast Alnico permanent magnets have the lowest reversible temperature coefficient, and the working temperature can be as high as 600 °C or more. Alnico permanent magnet products are widely used in a variety of instrumentation and other applications.
Samarium cobalt
Samarium cobalt (SmCo) is divided into SmCo5 and Sm2Co17 according to different compositions, which are rare earth permanent magnet materials of the first generation and the second generation respectively. Its development is limited by the scarcity and high price of raw materials. As the second generation of rare earth permanent magnets, samarium cobalt (SmCo) not only has a high magnetic energy product (14-28MGOe) and reliable coercivity, but also shows good temperature characteristics in the rare earth permanent magnet series. Compared with NdFeB, samarium cobalt is more suitable for working in high temperature environments (> 200 °C).
