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2021 China NdFeB neodymium magnet manufacturer manufacturing process technology

What are the manufacturing process technologies of NdFeB magnet manufacturers in 020? The airflow milling technology of NdFeB magnets has been widely used in the powder making process of magnetic materials and has been implemented for many years. With the maturity of the NdFeB stripping and hydrogen crushing process, new energy-saving and higher-efficiency airflow The mill was gradually developed and utilized. The jet mill used by the neodymium iron boron magnet is a circulating tube air jet destroyer, which is a complete destruction system composed of an air jet destroyer, a cyclone separator, a dust collector, and an induced draft fan. After the compressed air is filtered and dried, it is jetted into the destruction cavity at high speed through the Laval nozzle. At the intersection of multiple high-pressure airflows, the material is repeatedly collided, rubbed, and sheared and destroyed. The destroyed material rises under the effect of the fan's suction. The airflow moves to the classification area, and the strong centrifugal force generated by the high-speed rotating classification turbine separates the coarse and fine materials. The fine particles that meet the particle size requirements pass through the classification wheel and enter the cyclone separator and dust collector for collection. The coarse particles drop to the destruction area and continue to be destroyed. . Combined with the characteristics of rare earth magnetic materials that are easy to oxidize and require fine particle size, the entire process uses nitrogen as a power flow, and the return gas is compressed by a compressor to form a closed loop with a pipeline.
Manufacturing technology of NdFeB magnet manufacturers in 2021
 
 
At present, most NdFeB manufacturing companies use spin strips and hydrogen crushing techniques. After hydrogen crushing, the spin strips become very loose, and they are directly subjected to jet milling after hydrogen crushing. It not only improves the discharging speed, but also can grind the NdFeB magnetic powder to a finer size, which can reach 2.8 ~ 3.5 microns, so that the magnet grains can reach below 10 microns. The smaller the grains can increase the coercive force of the magnet. Improve the corrosion resistance of the magnet. In 2021, many companies have been able to develop high-efficiency, high-power jet milling equipment that is suitable for hydrogen crushing, and the output of powder may reach 150-200 kg per hour, or even higher. , This kind of jet mill uses a high-power frequency conversion screw compressor and accurate automatic nitrogen supplement technology, which makes the equipment operation more reliable and stable, and saves production costs as much as possible. The rare earth raw material of the magnet is smelted and cooled in a smelting furnace to form a stripping piece, and then enters the hydrogen crushing section, which is the coarse crushing and intermediate grinding of the rare earth alloy. The feed size is 100-0.1MM, and the powder size is 10-1000UM. . The powder particle size of the NdFeB permanent magnet should be 3-5UM, and it must be air-flow milled and finely ground. Hydrogenation fragmentation (HD) method is the expansion of hydrogen absorption lattice and dehydrogenation reduction to refine the particle size, and hydrogen absorption or dehydrogenation is a reversible chemical reaction process, and the physical and chemical reaction has its chemical composition and magnetic changes. NdFeB crystals absorb hydrogen, and the resulting hydride crystal lattice expands and generates heat, which is a chemical process; the swelling internal stress causes the NdFeB crystals to crack into a loose body, which is a physical phenomenon, and both proceed together; heating dehydrogenation After treatment, most of the main phase hydride is changed back to the original Nd2Fe14B powder, and part of the residual Nd-rich phase hydride requires advanced treatment. To make the hydrogen absorption process of NdFeB, the first one that absorbs hydrogen is the exposed Nd-rich phase, and then the main phase Nd2Fe14B reacts with H2. The composition of the main phase hydride is accompanied by an exothermic reaction, and the total heat can make the reaction. The object temperature rose to 300 degrees. The lattice constant increases and the thermal expansion process causes powdery cracking, and the HD powder of neodymium iron boron has undergone a sudden change.
 
  
Manufacturing technology of NdFeB magnet manufacturers in 2021
 
 
In 2021, NdFeB magnet manufacturer's manufacturing process technology, dehydrogenation turns Nd2Fe14Bhy into Nd2Fe14B, which is about to differentiate the hydride. The influence of temperature and pressure, 650. At C, the Nd-rich phase becomes soft and melts, and the temperature continues to rise to produce HDDE response. Now the optimal dehydrogenation temperature is 500. C. Under these conditions, all hydrogen of the main phase hydride is released, and the NdH3 of the neodymium-rich phase hydride is at 500. After C, part of the hydrogen is removed to become NdH2, 1040. C can completely discharge hydrogen from the main phase Nd2Fe14B. The green density of the magnetic field oriented forming link is about 3.2-3.8g/cm3, and the ideal density of the sintered NdFeB magnet should be about 7.5g/cm3, so in the limit comparison When large cylinders and squares are shortened, they are prone to cracking, deformed corners and out-of-size. Therefore, they need to be placed in an isostatic press to increase the density of the green body through isostatic pressing. The density is 4.5g/cm3, magnet manufacturers now except for low-function small columns (below งถ10mm) unequal static pressure, directly swing the box and enter the sintering furnace, other specifications must go through the isostatic pressing process, and the isostatic pressing of the green body is to avoid oil immersion And the surface is oxidized, vacuum packaging is required, and the oil is stripped before entering the furnace. The working principle of the isostatic press is the Pascal principle. The green body placed in the soft mold sleeve is placed in a closed ultra-high claw container, and the hydraulic oil is continuously pressed into the sealed container through the booster pump to make the The hydraulic pressure continues to increase, and the general operating pressure is 100~630MPa. The high-pressure liquid is uniformly applied to the outer surface of the rubber sleeve, and the granulated material in the rubber sleeve is compressed to make it shape. Because the characteristic of isostatic pressing is that the pressure in all directions is flat, the density of the formed blank is uniform, the arrangement structure is uniform, and isotropy. Magnet machining division: (1) Hole punching and hole punching: punching round and square bar magnets into cylindrical or square cylindrical magnets (2) Slicing processing: cutting cylindrical and square cylindrical magnets by a slicer (3) Shape processing: processing round and square magnets into tile-shaped, sector-shaped, groove-shaped or special-shaped magnets with other chaotic shapes. The shape slicing methods include: Grinding and slicing , Inner circle slicer slicing, multi-wire cutting slicing, wire cutting special-shaped processing and processing. In practical applications, the functions and shapes of neodymium iron boron magnets are various, such as: wafers, wafers (counterbore screw holes), cylinders, Rings, cylinders (with inner holes), squares, sectors, tiles, trapezoids, grooves, polygons and irregular shapes, etc. The scale, performance, service value, and current magnetization direction of each magnet of different shape are different.
 
Manufacturing technology of NdFeB magnet manufacturers in 2021
 
Regarding the introduction of magnet knowledge, there are two types of magnetizers currently in use, constant current magnetizers and pulse magnetizers. A. The working principle of the constant current magnetizer: A constant current direct current is passed through the coil to make the coil generate a stable magnetic field. Suitable for magnetizing low-coercivity permanent magnet materials, such as ferrite, low-coercivity neodymium iron boron. B. The operating principle of the pulse magnetizer: the instantaneous pulse high current is passed through the coil, so that the coil generates a short super strong magnetic field. Suitable for high-coercivity permanent magnet materials or occasions of chaotic multi-pole magnetization. 2021 NdFeB magnet manufacturer's manufacturing process technology is widely used in permanent magnet data production and application enterprises, suitable for the magnetization of various permanent magnet data parts and components, such as: AlNiCo series, ferrite series, rare earth permanent magnets Series, etc., have the characteristics of high efficiency and reliability. The equipment has no special requirements for the power supply equipment of the work site, and it is convenient and sensitive to use. Specifically speaking, pulse magnetization is to first charge a capacitor with a DC high-voltage voltage, and then discharge it through a coil with a very small resistance. The peak discharge pulse current can reach tens of thousands of amperes. This current pulse generates a strong magnetic field in the coil, which permanently magnetizes the hard magnetic material placed in the coil. The peak value of the pulse current is extremely high during the operation of the capacitor of the magnetizer, and the function of the capacitor to withstand the inrush current is very high. The structure of the magnetizer is relatively simple. In fact, it is an electromagnet with extremely strong magnetic force. It is equipped with iron blocks of various shapes as additional magnetic poles to form a closed magnetic circuit with the magnet to be magnetized. When magnetizing, the additional magnetic poles are arranged. And the magnet to be charged, only need to add the exciting current, it can be completed in an instant. The magnetization directions of circular or ring magnets include axial, radial, multi-level, and radiation magnetization. The NS poles of the square magnet will appear in pairs on the corresponding two faces of the six faces. After the magnet is magnetized, it can be packaged and shipped.
 
Manufacturing technology of NdFeB magnet manufacturers in 2021
 
The black pieces of the magnet blanks after slicing are bonded with 502 glue. In order to separate them, they need to be boiled in boiling water, remove the cutting oil, and separate the glue for subsequent inspection, chamfering, and electroplating. The inspection of the black piece is to inspect the semi-product after the boiled piece is dried. The thickness of the round piece is ±0.05mm, and the square piece is 0.07mm, or the inspection specification is drawn up according to the requirements of the customer's product. After the inspection, the black film will be sent to the chamfering room for chamfering. The chamfering is the first process of electroplating. The manufacturing process technology of the NdFeB magnet manufacturer in 2021 is to grind the right angle around the product to a certain degree according to customer requirements. The radian together makes the surface of the black sheet more lubricated, and adds the adhesion of the electroplated layer to make the surface of the electroplated layer smoother. The magnetic field orientation of magnet powder is one of the key processes for NdFeB magnet manufacturers to manufacture high-function sintered magnets. The intention of the magnetic field orientation is to align the easy magnetization direction of each powder particle in the same direction to make an anisotropic magnet, which has a large remanence Br along the direction of the c-axis orientation of the powder particle, thereby increasing the large magnetic energy of the magnet Product (BH)max value. The orientation of the magnet powder has a very important influence on the remanence Br and the large magnetic energy product (BH) max of the magnet. NdFeB magnet manufacturers have two intentions for the orientation molding of the powder: one is to limit the powder to a certain shape and size according to the user's application needs; the other is to maintain the magnetic field strength after the crystal orientation obtained in the magnetic field orientation. . The pressing method selected for the magnet is mould pressing and cold isostatic pressing. In 2021, the molding process in the manufacturing process of the NdFeB magnet manufacturer is the primary process of magnetic powder oxygen absorption. Therefore, the molding process has strict anti-oxidation measures, requiring the magnetic powder weighing or limiting the process to be operated under inert gas maintenance.
 
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