Ferromagnetic substances such as iron, cobalt, nickel, or ferrite are different. The electron spins in it can spontaneously arrange in a small range to form a spontaneous magnetization zone. This spontaneous magnetization zone is called a magnetic domain. After the ferromagnetic substance is magnetized, the internal magnetic domains are arranged neatly and in the same direction to strengthen the magnetism and form a magnet. The magnetization process of the magnet is the magnetization process of the iron block. The magnetized iron block and the magnet with different polarities generate attractive force, and the iron block is firmly "sticked" with the magnet. Natural magnets are ferroferric oxide and man-made magnets are usually steel. After the steel is magnetized, it will retain its magnetism. The natural permanent magnets generally refer to not only ferrite (ferroferric oxide), but also various permanent magnetic materials such as iron-cobalt-nickel alloys and iron rare-earth alloys, such as aluminum-nickel Cobalt, samarium cobalt, neodymium iron boron, these are also very common, very strong magnetism, these substances can be magnetized by a constant magnetic field, and after magnetization, they have magnetism and do not disappear. The composition of the artificial magnet is determined according to the magnetizable properties of various metals. The magnet is close to (touches) a magnetic substance, and the substance is induced to form a pole with a different name near one end, and a pole with the same name is generated at the other end. Magnet classification A. Temporary (soft) magnet a. Meaning: The magnetism is short-lived, and the magnetism disappears when the magnet is removed. b. Example: iron nails, wrought iron B. Permanent (hard) magnet a. Meaning: After magnetization, it can retain magnetism for a long time. b. Example: Steel nails are summarized as follows based on the above information: According to the principle of electromagnetic induction, a strong current can generate a strong magnetic field, and a strong magnetic field can be used to magnetize ferromagnetic materials. Because of the different magnetization characteristics of different materials, some materials It is easy to magnetize, and it is not easy to lose magnetism (loss of magnetism), and it can retain magnetism for a long time. Magnetizing this material produces a magnet. Use a magnetizer to magnetize hard magnets.
According to the principle of electromagnetic induction, current can generate a magnetic field, and use a strong magnetic field to magnetize hard magnetic materials. Magnetic materials generally called magnets are actually several different things: ordinary magnets, such as those used in general speakers, are iron gans. Oxygen magnet. They are made of iron scales (flaky iron oxides) that fall off the surface of the steel billet during the hot rolling process of the steel plant. After removing impurities, crushing and adding a small amount of other substances, they are placed in a steel mold for compression molding. , And then sintered in a reducing electric furnace (passing hydrogen) to reduce part of the oxide to ferrite, cooled, and then placed in an exciter to magnetize it. Better than them is magnetic steel: magnetic steel is real steel, and its composition is mainly high content of nickel in addition to iron. It is generally smelted in an intermediate frequency electric furnace (only one hundred and ten kilograms per furnace), and cast into shape. Because some of its planes have precision requirements, they generally need to be ground with a grinder. Then it is magnetized and becomes a product. This kind of magnet is used in all kinds of electricity meters that measure electricity. A better magnetic material is neodymium iron boron. They are substances containing the rare earth elements neodymium, iron and boron. The production is produced by the method of cemented carbide: it is made by powdering-mixing-molding-sintering-finishing-magnetizing. This kind of magnetic material has higher magnetic field strength, better performance and more expensive price. It is only used in the national defense industry and precision equipment. The rotor of the stepping motor in the electronic watch is that. Ah, this kind of magnetic material must be used in the maglev train. Ferrite permanent magnet materials include: strontium-ferrite permanent magnet materials and barium-ferrite permanent magnet materials, which are divided into isotropy and anisotropy. Ferrite permanent magnet materials are commonly used in speaker magnets. ; Metal permanent magnet materials mainly include AlNiCo permanent magnet materials and rare earth permanent magnet materials. Rare earth permanent magnet materials are divided into: samarium cobalt permanent magnet materials and neodymium iron boron permanent magnet materials. The rare earth permanent magnet material is made by powder metallurgy. Magnetic strength? I have not found convincing information for the time being.
There are too many classifications of magnets, I will briefly explain here: There are two main categories of magnetic materials: The first is permanent magnet materials (also called hard magnets): the material itself has the characteristics of preserving magnetism, and the second is soft magnetism ( Also called electromagnet): The magnet needs to be energized from the outside to generate magnetic force. What we mean by magnets, generally refers to permanent magnetic materials. There are also two major categories of permanent magnetic materials: One major category is: alloy permanent magnetic materials including rare earth permanent magnetic materials (neodymium Iron boron (Nd2Fe14B), samarium cobalt (SmCo), neodymium nickel cobalt (NdNiCO) The second category is: ferrite permanent magnet materials (Ferrite) are divided into different production processes: sintered ferrite (Sintered Ferrite), bonding Ferrite (Rubber Magnet), injection-molded ferrite (Zhusu Ferrite), these three processes are divided into isotropic and anisotropic magnets according to the orientation of the magnetic crystal. These are the main permanent magnet materials currently on the market, and some are eliminated due to production process or cost reasons, which cannot be used in a wide range, such as Cu-Ni-Fe (copper nickel iron), Fe-Co-Mo (iron, cobalt, molybdenum) ), Fe-Co-V (iron cobalt vanadium), MnBi (manganese bismuth), AlMnC (cobalt manganese carbon) 1. Rare earth permanent magnet materials (NdFeB Nd2Fe14B): According to different production processes, it can be divided into the following three types (1) , Sintered NdFeB (Sintered NdFeB)-(Sintered NdFeB permanent magnet is smelted after jet milling powder, with high coercivity value, and has high magnetic properties, its larger magnetic energy product (BHmax) ) Is more than 10 times higher than ferrite. Its own mechanical properties are also quite good, it can cut and process different shapes and drill holes. The working temperature of high-performance products can reach 200 degrees Celsius. Because of its easy material content Lead to rust, so the surface is treated with different coatings according to different requirements. (such as Zn, Ni, Au, Epoxy, etc.). Very hard and brittle, high resistance to demagnetization, high cost/performance ratio, not suitable for high Working temperature); (2) Bonded NdFeB (Bonded NdFeB)-Bonded NdFeB is to uniformly mix NdFeB powder with a binder such as resin, plastic or low melting point metal, and then compress and extrude Composite neodymium iron boron permanent magnets made by pressing or injection molding methods. The product is formed once, without secondary processing, and can be directly made into various complicated shapes. Bonded NdFeB has magnetism in all directions and can be processed into NdFeB compression molds and injection molds. High precision, better magnetic performance, good corrosion resistance and good temperature stability.
