How are magnets made?

Ferromagnetic substances such as iron, cobalt, nickel or ferrite are different. The electron spins in it can be spontaneously arranged in a small range to form a spontaneous magnetization region, which is called a magnetic domain. After the ferromagnetic substance is magnetized, the internal magnetic domains are arranged neatly and in the same direction, which strengthens the magnetism and constitutes a magnet. The process of attracting iron of a magnet is the magnetization process of the iron block. The magnetized iron block and the magnet of different polarities have an attractive force, and the iron block is firmly “sticked” to the magnet. Natural magnets are iron tetroxide and artificial magnets are usually steel. After the steel is magnetized, it will always retain its magnetic properties. The natural permanent magnets generally referred to are not only ferrite (iron tetroxide), but also various permanent magnet materials such as iron-cobalt-nickel alloys and rare earth alloys of iron, such as aluminum-nickel alloys. Cobalt, samarium cobalt, neodymium iron boron, these are also very common, and the magnetism is very strong. These substances can be magnetized by the constant magnetic field of the magnetic field, and they are magnetic and do not disappear after magnetization. The composition of artificial magnets is determined according to the magnetization properties of various metals. The magnet is close to (touches) the magnetic material, and the material near one end induces a synonymous pole, while the other end generates the same name pole. Magnet classification A. Temporary (soft) magnets a. Meaning: The magnetism is short-lived and disappears when the magnet is removed. b. Example: iron nails, wrought iron B. Permanent (hard) magnets a. Significance: After magnetization, the magnetism can be retained for a long time. b. Example: Steel nails are summarized as follows according to 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 substances, and due to the different magnetization characteristics of different substances, some substances It is easy to magnetize, and it is not easy to lose magnetism (loss of magnetism), and can retain magnetism for a long time. Magnetizing this material creates a magnet. Use a magnetizer to magnetize hard magnets.


According to the principle of electromagnetic induction, the current can generate a magnetic field, and the use of a strong magnetic field to magnetize a hard magnetic material is generally called a magnet. The magnetic material is actually several different things: ordinary magnets, such as those used in general speakers, are iron gantry. Oxygen magnet. They are iron scales (flaky iron oxides) that fall off the surface of the steel billet during the hot rolling process of the iron and steel plant. , and then sintered in a reducing electric furnace (passing hydrogen) to reduce part of the oxide to ferrite, cool it, and then put it into an exciter to magnetize it. Better than them are magnets: magnets are real steels, composed mainly of nickel, in addition to iron. It is generally smelted in an intermediate frequency electric furnace (only 100 kilograms per furnace), and cast and formed. Because some planes have precision requirements, they are generally ground with a grinder. Then it is magnetized to become a product. This kind of magnet is used in all kinds of electric meters that measure electricity. A better magnetic material is NdFeB magnetic material. They are substances containing the rare earth elements neodymium, iron and boron. It is produced by the method of cemented carbide: after powdering – mixing – molding – sintering – finishing – magnetization. Such magnetic materials have higher magnetic field strength, better performance and higher price. It is only used in national defense industry and precision equipment. The rotor of the stepper motor in the electronic watch is that. Ah, this magnetic material must be used in maglev trains. Ferrite permanent magnet materials include: strontium-ferrite permanent magnet material and barium-ferrite permanent magnet material, which are divided into isotropy and anisotropy. Speaker magnets generally use ferrite permanent magnet materials ; 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. Rare earth permanent magnet materials are made by powder metallurgy process. Magnetic strength? I haven’t found convincing information yet.


There are too many classifications of magnets, I will briefly say here: There are two main categories of magnetic materials: The first is permanent magnet materials (also called hard magnetism): the material itself has the characteristics of preserving magnetic force The second is soft magnetism ( Also called electromagnet): It needs external power to generate magnetic force. What we mean by magnet generally refers to permanent magnet materials. There are also two major categories of permanent magnet materials: one category is: alloy permanent magnet materials including rare earth permanent magnet materials (neodymium permanent magnet materials). Iron boron Nd2Fe14B), samarium cobalt (SmCo), neodymium nickel cobalt (NdNiCO) The second category is: ferrite permanent magnet materials (Ferrite) are divided into: sintered ferrite (Sintered Ferrite), bonding Ferrite (Rubber Magnet), injection 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 that cannot be widely used, 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): divided into the following three types according to different production processes (1) , Sintered NdFeB (Sintered NdFeB)——(Sintered NdFeB permanent magnets are smelted by jet milling and powder, with high coercivity value and high magnetic properties, and its larger magnetic energy product (BHmax ) is more than 10 times higher than that of ferrite. Its own mechanical properties are also quite good, and it can be cut and processed in different shapes and drilled holes. The working temperature of high-performance products can reach 200 degrees Celsius. Because of its easy material content Causes rusting, so different coating treatments are applied to the surface according to different requirements. (such as Zn, Ni, Au, Epoxy, etc.). Very hard and brittle, with high resistance to demagnetization, high cost/performance ratio, not suitable for high (2) Bonded NdFeB—bonded NdFeB powder is uniformly mixed with binders such as resin, plastic or low melting point metal, and then compressed and extruded. Composite NdFeB permanent magnets made by pressing or injection molding. The product is formed once, without secondary processing, and can be directly made into various complex shapes. The bonded NdFeB has magnetism in all directions and can be processed into NdFeB compression molds and injection molds. High precision, good magnetic properties, good corrosion resistance, good temperature stability.

Post time: Sep-06-2022