Since 1985, industrialization began simultaneously in Japan, China, and Europe and America. In the past 30 years, the global permanent magnet material industry has flourished, with magnetic properties constantly breaking records, and material varieties and grades continuously increasing. With the expansion of the market, its manufacturers are also increasing day by day, and many customers are inevitably caught in such confusion. How to judge the quality of products?
The most comprehensive judgment method: firstly, the performance of the magnet; 2、 Magnet size; 3、 Magnet coating.
Firstly, the guarantee of magnet performance comes from the control of the raw material production process
1. According to the requirements of the enterprise for manufacturing high-end, medium, or low-grade sintered neodymium iron boron, raw materials are selected and purchased according to the raw material composition specified in national standards.
2. The advanced production process directly determines the performance and quality of the magnet. At present, ******'s technologies include scale ingot casting (SC) technology, hydrogen crushing (HD) technology, and airflow grinding (JM) technology. Small capacity vacuum induction smelting furnaces (10kg, 25kg, 50kg) have been replaced by large capacity vacuum induction furnaces (100kg, 200kg, 600kg, 800kg). SC (StripCasting) rapid solidification casting technology has gradually replaced large ingots (ingots with a thickness greater than 20-40mm in the cooling direction), while hydrogen crushing (HD) technology and airflow milling (JM) have replaced jaw crushers, disc mills, and ball mills (wet milling), ensuring powder uniformity and facilitating liquid phase sintering and grain refinement.
3. In terms of magnetic field orientation, China is the only country in the world that adopts two-step compression molding. During orientation, small pressure vertical molding is used, and finally quasi isostatic pressing is used, which is one of the most important characteristics of China's sintered neodymium iron boron industry.
4. Moreover, monitoring the quality of the production process is very important, which can be controlled through detection methods such as SC sheet thickness measurement and JM powder particle size distribution. High quality products all depend on the control of the production process, but customers will definitely be confused. How to judge the performance of the products I purchase? The Chinese Academy of Metrology has developed various models of permanent magnet material technical magnetic parameter measurement instruments. Pulse magnetic field Magnetometer (PFM) is a kind of test instrument for testing ultra-high Coercivity permanent magnets, which is mainly used to meet the requirements of high Coercivity permanent magnets in the field of electric vehicles and large permanent magnet motors.
Customers can select their own brand of NdFeB according to the magnet parameters Br (remanence), Hcb (Coercivity), Hcj (intrinsic Coercivity), and (BH) max (maximum magnetic energy product). At the same time, these four parameters are the criteria to determine whether the product is produced according to customer requirements.
Secondly, the guarantee of magnet size depends on the processing strength of the factory