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Home » News Center » Corporate news » How to judge the quality of sintered ndfeb magnet?
How to judge the quality of sintered ndfeb magnet?
Authors:handler Time:2017-07-07 03-45-44

The new week is accidentally come, calculate not today, again two days shift the Mid-Autumn festival, today we still say magnetic material. Every time a magnetic material is said, people who may be engaged in this industry for many years have a thorough understanding of the various aspects of magnetic materials and are experts. But goose, believe that there are some people who have just entered the industry or are interested in the industry, have not seen the magnetic material.


Today want to say is not a wide range of magnetic materials, we will point a small point, do not think that it is no meaning to small, believe that everyone is very concerned about the content of the to judge the quality of sintered ndfeb magnet? Sinter ndfeb is no stranger, its production process and so on we have already said before.

Sintered nd-fe-boron permanent magnet, as one of the important substances to promote modern technology and social progress, is widely used in the following fields:


Since 1985, the industrialization of Japan, China and Europe and the United States has also begun. In the last 30 years, the world's permanent magnet material industry has been booming, and the magnetic field has been continuously updated with the number of materials and the number of materials increasing. With the development of the market and the increasing number of manufacturers, many customers are inevitably caught in such confusion, how to judge the pros and cons of the nd-boron magnet?

The most comprehensive method of judgment


The magnet performance

The magnet size

Magnetic coating


Production of raw materials


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


1. According to the requirements of the company to make high-grade or middle-grade or low-grade sintered ndfeb, the raw materials are selected according to the national standard.


2. The advanced technology of production determines the performance quality of the magnet directly. At present, the most advanced technologies are scale casting (SC) technology, hydrogen crushing (HD) technology and airflow grinding (JM) technology.


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

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


SC (StripCasting) rapid casting technique

The large ingot has been gradually replaced


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

Replace the jaw crusher, disc mill, ball mill (wet legal powder)


3, magnetic field orientation, our country is the only country adopts two-step forming technology in the world, orientation with a small vertical moulding pressure, finally USES the isostatic pressing molding, this is one of the most important characteristics of sintered ndfeb industry in our country.


4. Moreover, the monitoring of the quality of production process is very important, which can be controlled by the measurement of SC chip thickness and the distribution of the size distribution of JM powder. The China institute of metrology has developed various types of magnetic parameter measuring instruments for permanent magnetic materials.

Pulse magnetic field magnetometer (PFM) - test of ultra-high coercive force permanent magnet


To be honest, it's a little hard to tell, but according to the magnetic parameters Br (remanent), Hcb (coercive force), Hcj (Hcj), (BH) Max (maximum magnetic energy product), select the nd-b plate number you need.


Factory processing


Secondly, the size of the magnet depends on the processing power of the factory.


The actual use of the nd-ti-boron permanent-magnet is a variety of shapes:

The permanent magnets of each shape have different sizes, and the production process is difficult to achieve once. The general production process is:


Produce large (large size) of the billet - - sintering and tempering - - mechanical processing (including cutting, punching) - - > grinding - > surface coating (coating) - > > detection properties, surface quality and dimensional accuracy (magnet) magnetization - - packaging - - - - > the factory.


1. Mechanical processing is divided into three categories:

Cutting process: the cylindrical and square cylindrical magnets are cut into round and square pieces.

Contour machining: the circular, square magnet is processed into a fan, tile, or a magnet with grooves or other complex shapes;

(3) hole processing: the round rod and the square rod are processed into cylindrical or square cylindrical magnets. The processing methods include: grinding slice processing, edm cutting processing and laser processing.


2. The surface of the sintered ndfeb permanent magnetic element is generally required to be smooth and to achieve certain precision. The surface of the magnetic surface of the raw material shall be machined on the surface.


It is a common grinding method for the nd-nd-nd-nd-ti-borium permanent-magnet alloy.

Square: flat surface grinding, double end surface grinding, inner circle grinding, circular grinding, etc

Cylinder: commonly used without core grinding, double end face grinding, etc

Watt-shaped, fan-shaped and VCM magnets: use a multi-station grinding machine


A qualified magnet is not only required to meet the standard of performance, but the control of tolerance also directly influences its application. And the size of the security directly depend on the processing power of the factory, processing equipment as the economy and the market demand is constantly updated, the trend of more efficient equipment and industrial automation, is not only meet customers' growing demand for the product accuracy, but also save manpower and cost, make it more have market competitiveness.


Magnetic coating


Thirdly, the quality of the magnet coating determines the application life of the product.


Experiment, 1 cm3 of sintered ndfeb permanent magnet stay 51 days in 150 ℃ in air, will all be oxidation corrosion. It's more likely to corrode in a weak acid solution. In order to make the nd-ti-boron permanent magnet durable, it is required to have 20-30 years of service life, and it must undergo surface anti-corrosion treatment.


At present, the sintering nd-nd-pboron permanent-magnet system is widely adopted

Plating metal

Electroplating + chemical metallization

Electrophoretic coating and phosphating treatment


1, phosphating is used in some special cases: (1) in ndfeb magnet products because turnover, save the time is too long and not clear the surface of the follow-up processing method, using the phosphating is simple; (2) when the magnet requires epoxy adhesive bonding, paint, etc., the adhesive force of the epoxy organic materials such as glue, paint and other epoxy organic materials needs to have good penetration performance. The phosphating process can improve the infiltration ability of the magnetic surface.


2. Electrophoresis coating has become one of the most widely used anticorrosive surface treatment technologies. Because it is not only good with the surface of the porous magnet, but also has the corrosion of salt resistant fog, acid and alkali resistance, and excellent corrosion resistance. However, compared with coating coating, it has poor heat resistance and heat resistance.


I can't understand you so much. I'll just throw you two test experiments.

The experiment of the experiment (also known as PCT experiment) was conducted to test the corrosion resistance of the nd-nd-ti-boron permanent magnet in humid and high-temperature environment.

Salt fog experiment - a rapid corrosion prevention experiment for sintered nd-ferroboron, which has been treated by corrosion resistant coating.