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    How To Judge The Quality Of Sintered NdFeB Magnets?

    Dongyang Aviation Magnetic Ltd | Updated: Aug 14, 2017

      How to judge the quality of sintered NdFeB magnets?

      Today to say is not a wide range of magnetic materials, we gather a small point, do not think that there is no sense of small, I believe we are very concerned about the content, how to judge the quality of sintered NdFeB magnets? Sintered NdFeB we are not familiar with it, its production process and other content we have said before.

      Sintered NdFeB permanent magnet, as one of the important substances to promote contemporary technology and social progress, is widely used in the following areas:

      Since 1985 in Japan, China and Europe and the United States at the same time began to industrialization, which nearly 30 years, the global permanent magnet materials industry booming, magnetic properties continue to refresh the record, the variety of materials and grades continue to increase. With the expansion of the market, its manufacturers are also increasing, and many customers will inevitably fall into such a puzzle, how to judge the pros and cons of NdFeB magnets it?

      The most comprehensive method of judgment

      First of all, the protection of magnet performance from the raw material production process control.

      1, according to the enterprise manufacturing high-grade or mid-range or low-grade sintered NdFeB requirements, in accordance with national standards of raw materials to buy raw materials.

      2, the production process of advanced or not directly determine the performance of the magnet quality. At present, NdFeB magnet the most advanced technology is scale ingot (SC) technology, hydrogen crushing (HD) technology and airflow grinding (JM) technology.

      Small capacity vacuum induction smelting furnace (10kg, 25kg, 50kg) was

      Large capacity (100kg, 200kg, 600kg, 800kg) vacuum induction furnace replaced

      SC (StripCasting) technology

      Has gradually replaced large ingots

      Hydrogen crushing (HD) technology and airflow grinding (JM)

      Replace the jaw crusher, plate mill, ball mill (wet milling)

      3, the magnetic field orientation, China is the world's only two-step compression molding of the country, the orientation with a small pressure vertical molding, and finally the use of quasi-isostatic pressing, which is China's sintered NdFeB industry, one of the most important features The

      4, and the monitoring of the quality of the production process is very important, can be measured by the SC film thickness and JM powder particle size distribution and other detection methods for control. NdFeB magnet China Institute of Metrology has developed a variety of models of permanent magnet materials technology magnetic parameters measuring instruments.

      Pulsed Magnetic Field Magnetometer (PFM) - Test for high coercivity permanent magnets

      (BH) max (maximum magnetic energy product) selected according to the magnet parameters Br (remanence), Hcb (coercivity), Hcj (intrinsic coercivity), (BH) max (maximum magnetic energy product) Grade.

      Second, the protection of the size of the magnet depends on the processing strength of the plant.

      The practical application of NdFeB permanent magnet shape is varied:

      Each shape of the permanent magnets have different sizes, the production process is difficult to achieve a molding. The general production process is:

      (Including cutting, punching) → → grinding processing → → surface coating (coating) → → detection (magnet performance, surface quality and size), the production of large (large size) of the material → → sintering and tempering → → mechanical processing Precision) → → magnetization → → → → → factory packaging.

      1, mechanical processing is divided into three categories:

      Cutting: the cylindrical, square column magnet cut into a round, square sheet;

      Machining: Machining a circular, square magnet into a fan, tile, or groove or other complex shaped magnet;

      (3) drilling processing: the rod, square rod-like magnet into a cylindrical or square tube magnet. The processing methods are: NdFeB magnet grinding section processing, EDM cutting and laser processing.

      2, sintered NdFeB permanent magnet components on the surface of the general requirements of smooth and achieve a certain accuracy, rough delivery of the surface of the magnet surface grinding required.

      Monolithic NdFeB permanent magnet alloy commonly used grinding processing methods are:

      Box: plane grinding, double face grinding, internal grinding, cylindrical grinding and so on

      Cylinders: commonly used without core grinding, double face grinding and so on

      Tile type, fan and VCM magnet: with multi-station grinder

      A qualifying magnet, not only the performance of the standard, the size of the tolerance control also directly affect its application. The size of the protection depends directly on the processing strength of the factory, processing equipment with the economic and market demand is constantly updated, more efficient equipment and industrial automation trends, not only to meet customer demand for increasing product precision, but also Saving manpower and cost, so that it has more market competitiveness.

      Again, the quality of the magnet coating directly determines the service life of the product.

      Experiments show that 1cm3 sintered NdFeB permanent magnet placed in the air at 150 ℃ for 51 days, will be all oxidized corrosion. It is more susceptible to corrosion in weak acid solutions. In order to make the NdFeB permanent magnet durable, NdFeB magnet it requires 20-30 years of service life, which must withstand surface corrosion treatment.

      At present, the sintered NdFeB permanent magnet manufacturing industry commonly used electroplating + electroless plating

      Electrophoretic coating and phosphating treatment and other methods

      1, in some special circumstances will also use phosphating: (1) in the NdFeB magnet products because of the turnover, the preservation of the time is too long and not clear follow-up surface treatment methods, the use of phosphate is simple; 2) When the magnet needs epoxy adhesive bonding, painting, glue, paint and other epoxy organic adhesive force requires a good substrate invasion performance. Phosphating process can improve the invasion of the magnet surface.

      2, electrophoretic coating has become widely used anti-corrosion surface treatment technology. Because it is not only with the porous magnet surface adhesion is very good, but also has salt spray resistance, acid, alkali and other corrosion, NdFeB magnet excellent corrosion resistance. But compared with the spray coating its poor resistance to wet heat.