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How To Judge The Quality Of Sintered NdFeB magnets?

Nov. 18, 2019

Sintered NdFeB permanent magnets, as one of the important materials to promote contemporary technology and social progress, are widely used in the following fields: computer hard drives, nuclear magnetic resonance imaging, electric vehicles, wind power, industrial permanent magnet motors, consumer electronics (CD, DVD, mobile phone, audio, copier, scanner, camcorder, camera, refrigerator, TV, air conditioner, etc.) and magnetic machinery, magnetic levitation technology, magnetic transmission and other industries.


Since 1985, it has begun industrialization in Japan, China and Europe and the United States at the same time. In the past 30 years, the global permanent magnetic material industry has developed vigorously, the magnetic performance has continuously set a record, and the variety of materials and brands has continued to increase. With the expansion of the market, its manufacturers are increasing, and many customers are inevitably caught in this confusion. How to judge the quality of the product? Ring Neodymium Magnet Factory will tell you next.

Ring Neodymium Magnet

Ring Neodymium Magnet


The most comprehensive judgment method: First, the performance of the magnet; Second, the size of the magnet; Third, the coating of the magnet.


First, the guarantee of magnet performance comes from the control of the raw material production process


1. Purchasing raw materials according to the requirements of enterprises for manufacturing high-end or mid-range or low-grade sintered neodymium-iron-boron, and according to the raw material composition specified by national standards.


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 Small capacity vacuum induction smelting furnaces (10kg, 25kg, 50kg) have been replaced by large capacity (100kg, 200kg, 600kg, 800kg) vacuum induction furnaces.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 (ingots with a thickness greater than 20-40 mm in the cooling direction), and hydrogen crushing (HD) technology and jet mill (JM) have replaced jaw crushers and disc mills. The machine and ball mill (wet milling) ensure the uniformity of the powder and are conducive to 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. 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 NdFeB.


4. Moreover, the monitoring of the quality of the production process is very important, and high-quality products depend on the control of the production process.


Second, the guarantee of magnet size depends on the processing strength of the factory


The shapes of practically used NdFeB permanent magnets are various, such as discs, Cylinder Neodymium Magnet, square plates, squares, square pillars; tiles, fans, trapezoids, polygons, and various 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: Cut Square Block Neodymium Magnet into discs and squares;

(2) Shape processing: round and square magnets are processed into fan-shaped, tile-shaped or grooved or other complex shaped magnets;

(3) Hole punching process: round or square rod magnets are processed into cylindrical or square tube magnets. The processing methods are: grinding and chip processing, EDM cutting and laser processing.


A qualified magnet does not only need to meet 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.

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