Sintered NdFeB is widely used in household appliances, transportation, medical health, aerospace, and other fields due to its ultra-high magnetic energy density and good service characteristics. To meet the use requirements of NdFeB magnets in different fields and objectively evaluate the applicability and quality of the magnets, it is usually necessary to conduct various index tests on NdFeB magnets. Generally speaking, we divide the testing content into three Aspects: First, product appearance size and physical properties, second, product magnetic properties, and third, product performance auxiliary testing items.
Appearance Size and Physical Performance Testing
The appearance size and physical properties of NdFeB products are the basic requirements for product use. A good product must not only meet the magnetic properties but also need various sizes, coatings, mechanical properties, etc. that meet actual needs to meet basic assembly and different environments. Requirements.
| Test items | Testing equipment | Detection Indicator | Factors affecting indicators | Testing purpose |
| Size | Calipers, micrometers, pass and stop gauges, projectors, CCD visual detectors | Length, width, thickness dimensions, verticality, parallelism, R angle, C angle, etc | Machining equipment, testing tools, instrument accuracy, calibration employee skills, etc. | Ensure product assembly characteristics and quality performance consistency |
| Exterior | Visual observation, comparison card, tapping or developer, etc. | Pinholes, corners, scratches, cracks, etc. | Material formula, production process, machining process, etc. | Reduce product corrosion resistance, performance, mechanical failure risk, etc. |
| Coating Bonding Strength | Mechanical testing machine or planning test | The degree and force of coating peeling, and the peeling ratio of the planned area | Electroplating pre-treatment and electroplating process, coating types | Guaranteed electroplating corrosion resistance |
| Mechanical properties | Mechanical testing machine | Tension, compression, etc. | Material formula, production process, machining process, product specifications | Reduce the risk of product cracking during use |
| Corrosion resistance | Salt spray test chamber, high-pressure accelerated aging test chamber | Seed loss, salt spray, etc. | Electroplating process, coating, film thickness, environmental conditions, etc. | Reduce the risk of product corrosion in harsh environments |
The magnetic properties of NdFeB are the main requirements for use. Only products that strictly meet the magnetic properties requirements can fully exert their effectiveness in the fields we need and carry out stable applications. This requires us to strictly test the magnetic performance indicators of NdFeB.
| Test Items | Testing equipment | Detection Indicator | Factors affecting indicators | Testing purpose |
| Magnetic Properties | Permanent magnet measuring instruments, such as the NIM series of Metrology Institute, Mianyang bipolar series, foreign Hirst, etc. | Normal/high-temperature Br, Hcb, Hcj, Hk/Hcj, (BH)max, Br and Hcj temperature coefficient, inflection point, recovery permeability, etc. | Material formula, production process, processing accuracy, tester accuracy, test environment, etc. | Test various indicators of product performance to meet product usage requirements, etc. |
| Surface Magnetism | Surface magnetic distribution measuring instrument, Tesla meter, etc. | The size and distribution uniformity of surface magnetism in the center or specific area, etc. | Residual magnetism, product dimensions, measurement methods, etc. | Check the magnetic field size in local areas of the product |
| Magnetic Moment | Magnetic moment tester, flux meter, etc. | Magnetic moment value | Residual magnetism, product size, etc. | More accurately reflects the magnetic properties of the product |
| Thermal Demagnetization | Magnetic flux meter, oven, etc. | Magnetic flux, magnetic loss percentage | A material composition such as Co, Nd, Gd, etc., product Pc value, Hcj, Hk/Hcj, etc. | More realistic magnetic stability of reaction products in high-temperature environments |
In terms of magnetic properties, in the early days, everyone focused on the two indicators of remanence Br and intrinsic coercive force Hcj. Now, more and more users are paying attention to magnetic moment and thermal demagnetization. In fact, we use magnetic steel mainly for its two important characteristics, one is the magnetic energy density per unit volume, and the other is the magnetic stability of high-temperature operation. It is more reasonable to use magnetic moment and thermal demagnetization to evaluate. Magnetic steel selected using thermal demagnetization indicators will undoubtedly have better service reliability and higher cost performance.
Auxiliary testing items
| Test items | Testing equipment | Detection Indicator | Factors affecting indicators | Testing purpose |
| Density | Solid density meter | Archimedes displacement method to calculate the weight and volume ratio | Blank density | Material components, sintering process, preparation process |
| Oxygen, nitrogen, and hydrogen content | Oxygen, nitrogen, and hydrogen tester | The sample is converted at high temperatures to produce co, CO2, N2, and H2 for detection. | O, N, H content | Raw material preparation process |
| Carbon and sulfur content | Infrared carbon and sulfur analyzer | The high temperature causes the carbon and sulfur in the sample to burn to form oxides for detection. | C, S content | Raw material preparation process |
| Element | plasma emission spectrometer | Atoms transition after ionization and detect the released electromagnetic wave energy, which corresponds to elements with different characteristic spectra. | Such as Pr, Nd, Fe, Cu, B, and other elements | Formula design, raw material composition, production process, testing accuracy |
| Microscopic | Scanning electron microscope, energy spectrometer | Analyze sample surface properties through secondary electrons, backscattered electrons, and characteristic X-ray signals | Grain appearance, morphology, and size, microscopic composition | Sample preparation, electron microscope resolution, and accuracy |
The auxiliary testing items of NdFeB are mainly to check whether the product performance meets expectations during the production process and to verify whether there are any defects in the production process; when abnormal conditions occur or new products are developed, the product composition and appearance are analyzed and confirmed.