Ambient temperature. Since the sintered NdFeB magnet has a negative temperature coefficient (αBr<-0.13%/℃, αHcj<-0.6%/℃), the instantaneous maximum temperature and the continued maximum temperature of the operating environment will demagnetize the magnet itself to different degrees. , Including reversible and irreversible, recoverable and irreversible.
environment humidity. The neodymium iron boron magnet itself is easy to corrode and oxidize. Generally, we adopt the method of surface treatment to protect the permanent magnet, but it cannot fundamentally deal with the influence of environmental humidity on the magnet. The drier the environment, the longer the service life of the magnet. How to measure the unevenness of magnetic function?
There are three main parameters: remanence Br (ResidualInduction), the unit Gauss, is a parameter that measures the strength of the magnetic field that the magnet can supply to the outside; coercive force Hc (CoerciveForce), the unit is Oersteds, is a parameter that measures the ability to resist demagnetization; the magnetic energy product BHmax , The unit Gauss-Oersteds, is a physical quantity that characterizes how much energy can be stored.
Permanent magnet high temperature resistant magnets are divided into two categories: the top category is: metal alloy high temperature magnets including neodymium iron boron high temperature magnets Nd2Fe14B), samarium cobalt high temperature magnets (SmCo), aluminum nickel cobalt high temperature magnets (ALNiCO) second The main categories are: Ferrite permanent magnet materials (Ferrite) high temperature resistant magnets have special atomic internal structure contrast, and they have magnetic moments themselves. Varieties of high temperature resistant magnets: Shape type high temperature resistant magnets: square high temperature resistant magnets, tile-shaped high temperature resistant magnets, special-shaped high temperature resistant magnets, cylindrical high temperature resistant magnets, circular high temperature resistant magnets, disc high temperature resistant magnets, high temperature resistant magnets , Magnetic frame high temperature magnets, characteristic high temperature magnets: samarium cobalt magnets, neodymium iron boron high temperature magnets, ferrite high temperature magnets, alnico high temperature magnets, iron chromium cobalt high temperature magnets, professional high temperature magnets : Magnetic components, motor high temperature magnets, rubber high temperature magnets, strong high temperature magnets, plastic magnets, etc. High-temperature resistant magnets are divided into permanent high-temperature resistant magnets and soft magnets. Permanent high-temperature resistant magnets are combined with strong magnets, so that the spin and electronic angular momentum of the magnetic substance are placed in a fixed direction. Method of applying magnetic force) When the current is removed, the soft iron will gradually lose its magnetism.
High temperature resistant magnets with different properties have different composition characteristics, and the size of the magnetic force is also different. The usual high temperature resistant magnets can be divided into the following four types according to different types:
1. Neodymium iron boron high temperature resistant magnet: it is the high temperature resistant magnet with the highest commercial function found now. We call it the magnet king. It has extremely high magnetic function and its maximum magnetic energy product (BHmax) is higher than that of ferrite (Ferrite) 10 Times more. Its own mechanical processing function is also quite good. The operating temperature can reach up to 200 degrees Celsius. Moreover, its texture is hard, its function is stable, and its cost performance is very good. However, due to its strong chemical activity, it is necessary to coat its surface. (Such as Zn, Ni, electrophoresis, passivation, etc.).
2. Ferrite high temperature magnet: its main raw materials include BaFe12O19 and SrFe12O19. It is made by ceramic technique and has a relatively hard texture. It is a brittle material. Due to its excellent temperature resistance, low price and moderate function, ferrite high temperature magnets have become the most widely used permanent magnets.
3. Al-Ni-Co high-temperature resistant magnet: It is an alloy composed of aluminum, nickel, cobalt, iron and other trace metal elements. Casting skills can be processed into different standards and shapes, and the machinability is excellent. Cast AlNiCo permanent magnets have the lowest reversible temperature coefficient, and the operating temperature can be as high as 600 degrees Celsius. Alnico permanent magnet products are widely used in various instruments and other applications.
4. Samarium cobalt (SmCo) is divided into SmCo5 and Sm2Co17 according to the composition. Due to the high price of its materials, its development is restricted.
Samarium cobalt (SmCo), as a rare earth permanent high temperature magnet, not only has a high magnetic energy product (14-28MGOe), reliable coercivity and outstanding temperature characteristics. Compared with neodymium iron boron high temperature magnets, samarium cobalt high temperature magnets are more suitable for working in high temperature environments. Hang the middle point of the bar-shaped high temperature magnet with a thin line. When it stops, its two ends will point to the south and north of the earth. The end that points to the north is called the north pole or the N pole, and the end that points to the south is the guide pole or S pole.