NdFeB is widely used in energy, transportation, machinery, medical, IT, home appliances and other industries, especially with the development of the knowledge economy represented by information technology, it has continuously brought new functional materials to the rare earth permanent magnet NdFeB industry. use. The following is a brief introduction on how to judge the quality of NdFeB. I hope it can help you to a certain extent. The most comprehensive judgment method: First, the performance of the magnet; Second, the size of the magnet; Third, the coating of the magnet. First of all, the guarantee of the performance of the magnet comes from the control of the raw material production process. 1. Purchasing raw materials according to the requirements of national standards for raw materials according to the requirements of the company for manufacturing high-end, mid-range or low-grade sintered neodymium iron boron. 2. The advanced production process directly determines the performance and quality of the magnet. Currently the most advanced technologies are scale ingot (SC) technology, hydrogen crushing (HD) technology and jet mill (JM) technology. Small capacity vacuum induction smelting furnaces (10kg, 25kg, 50kg) have been replaced by large capacity (100kg, 200kg, 600kg, 800kg) vacuum induction furnaces. SC (StripCasting) rapid solidification slab technology has gradually replaced large ingots (casting with a thickness greater than 20-40mm in the cooling direction).
Ingot), hydrogen crushing (HD) technology and jet mill (JM) replaced jaw crushers, disc mills, ball mills (wet milling), ensured the uniformity of the powder, and facilitated liquid phase sintering and grains. Refinement. 3. In terms of magnetic field orientation, China is the only country in the world that adopts two-step compression molding. Orientation is performed with small pressure and vertical compression molding. Finally, quasi-isostatic pressing is used. This is one of the most important characteristics of China's sintered neodymium iron boron industry . 4. The quality monitoring of the production process is very important. It can be controlled through detection methods such as SC film thickness measurement and JM powder particle size distribution. High-quality products depend on the control of the production process, but customers will be very puzzled. How can I judge the performance of the product I purchased? China Institute of Metrology has developed a variety of models of permanent magnetic material technology magnetic parameter measurement instruments. Pulse magnetic field magnetometer (PFM) is a testing instrument for testing ultra-high coercivity permanent magnets, mainly to meet the needs of the electric vehicle field and large permanent magnet motors
High-coercivity permanent magnet. Customers can choose the NdFeB grade they need according to the magnet parameters Br (residual magnetism), Hcb (coercive force), Hcj (internal coercive force), (BH) max (maximum magnetic energy product). The parameter is the standard for judging whether the product is produced according to customer requirements. Secondly, the guarantee of the size of the magnet depends on the processing strength of the factory. The shape of the practically applied NdFeB permanent magnets is various, such as discs, cylinders, cylinders (with inner holes); square plates, squares, square columns; Tiles, fans, trapezoids, polygons, and irregular shapes. Each shape of the permanent magnet has a different size, and it is difficult to make a single molding in the production process. The general production process is: Mr. produces a large (large size) blank, after sintering and tempering treatment, and then through mechanical processing (including cutting, drilling) and grinding, surface plating (coating) treatment, and then Inspection of magnet performance, surface quality and dimensional accuracy, then magnetization, packaging and shipment. 1. Mechanical processing is divided into three categories: (1) Cutting processing: cutting cylindrical and square cylindrical magnets into discs and squares; (2) Shape processing: processing circular and square magnets into fan-shaped, tile-shaped or Magnets with grooves or other complex shapes; (3) Hole punching: round or square rod magnets are processed into cylindrical or square cylindrical magnets. The processing methods are: grinding and chip processing, EDM cutting and laser processing. 2. The surface of sintered neodymium iron boron permanent magnet components is generally required to be smooth and reach a certain accuracy, and the surface of the magnet delivered from the blank needs to be surface polished. Common grinding methods for square neodymium iron boron permanent magnet alloys include surface grinding, double end grinding, internal grinding, and external grinding. Coreless grinding and double end grinding are commonly used for cylinders. Tile, sector and VCM magnets use multi-station grinders.
合格 A qualified magnet does not only need to meet the performance standards, the control of dimensional tolerance directly affects its application. The guarantee of size directly depends on the processing strength of the factory. With the economic and market requirements, the processing equipment is constantly updated. The trend of more efficient equipment and industrial automation is not only to meet the increasing demand of customers for product accuracy, but also Saved manpower and costs, making it more market competitive. Thirdly, the quality of the magnet coating directly determines the application life of the product. It is known that the 1.3cm sintered neodymium iron boron permanent magnet is left in the air at 150 ° C for 51 days, and will be oxidized and corroded. It is more easily corroded in weak acid solutions. In order to make the NdFeB permanent magnet durable, it is required to have a service life of 20-30 years. It must be subjected to a surface anti-corrosion treatment to resist the corrosion damage of the magnet to the corrosive medium. At present, the sintered NdFeB permanent magnet manufacturing industry generally adopts methods such as electroplating metal, electroplating + electroless metal plating, electrophoretic coating and phosphating, etc., to coat the surface of the magnet with an additional spacer to isolate the surface of the magnet from the corrosive medium. In order to prevent the media from invading the magnet. 1. Generally, zinc plating, nickel plating + copper + nickel, nickel plating + copper + chemical nickel plating are the three main processes. For other metal plating requirements, other metal plating is generally applied after nickel plating. 2. Phosphating is also used in some special cases: (1) When the neodymium-iron-boron magnet products are turned over and stored for too long and the subsequent surface treatment method is not clear, using phosphating is simple and easy; ( 2) When the magnet requires epoxy glue bonding, painting, etc., the adhesion of epoxy organic matters such as glue, lacquer, etc. requires the matrix to have good wetting performance. The phosphating process can improve the infiltration ability of the magnet surface. 3. Electrophoretic coating has become one of the widely used anti-corrosion surface treatment technologies. Because of
Not only has a good bonding force with the surface of porous magnets, but also has corrosion resistance to salt spray, acid, and alkali, and excellent corrosion resistance. However, its heat and humidity resistance is poor compared to sprayed coatings. Customers can choose the coating according to their product work requirements. With the expansion of motor application fields, customers have higher requirements for the corrosion resistance of NdFeB. The HAST test (also known as the PCT test) is specifically designed to test the corrosion resistance of sintered NdFeB permanent magnets in humid and high temperature environments. And how do customers judge whether the coating meets the requirements? The purpose of the salt spray experiment is to perform a rapid anti-corrosion experiment on the sintered neodymium-iron-boron magnet with a surface treated with anti-corrosion coating. At the end of the experiment, the sample is taken out of the test box and dried. Use your eyes or a magnifying glass to observe whether there are spots on the surface of the sample and the change in the size of the box. In terms of performance, its Br (remanent magnetism), Hcb (coercive force), Hcj (internal coercive force), (BH) max (maximum magnetic energy product), and demagnetization curve can be detected through performance; dimensional tolerances can be measured by vernier calipers Measure its accuracy; on the coating, you can observe the color and brightness of the coating with the naked eye and through detection methods such as binding force and salt spray test; the overall appearance, mainly with the naked eye or a magnifying glass, or an optical microscope (for products with a linearity of less than 0.2mm), The surface of the magnet is smooth, there are no particles and foreign objects visible to the naked eye, no spots, no edges and corners, and the appearance is qualified. In summary, only when the customer understands the production process and the requirements of the product can he correctly judge the product's eligibility. In summary, it is the control of performance, the control of dimensional tolerances, the detection of coatings and the evaluation of appearance. Xiamen everbeen Magnetic Industry Co., Ltd. is specialized in rare earth permanent magnet materials, magnetic devices, magnetic
High-tech enterprise in R & D, production and sales of flexible tools and magnetic material related products. The company has passed ISO9001 system certification, and produces and sells rare earth permanent magnet products with various performances and shapes. In addition, the company relies on its extensive experience in magnetic material machining and strong production capacity, is committed to the development, production and sales of magnetic components and magnetic tools, to provide customers with high-quality magnetic components and magnetic tool products. At present, our company's NdFeB permanent magnet materials and magnetic components have been widely used in machinery processing, electro-acoustics, motors, instruments, automatic control, wind power generation, luggage, toys, craft jewelry and other fields. We are willing to develop together with customers at home and abroad and create a better future with a sincere attitude.
