Sagawa, Hadjipanayis, and Croat independently discovered Nd-Fe-B based rare earth permanent magnets almost simultaneously in 1984. The main phase of this material is Nd2Fe14B and its maximum energy products achieved 280kJ/m3 at that time. Besides the relatively lower Curie temperature, Nd2Fe14B is an ideal and promising permanent magnet material. The successful development of Neodymium magnets announced the birth of the third-generation rare earth permanent magnets. Sintered Neodymium magnets, also known as Neo magnets, offer the strongest magnetic power today. They are particularly suitable for high volume production in the variety of shapes and sizes. Precise dimensional control can be obtained in the machining processes. With these advantages, sintered Neodymium magnets have been widely applied in lots of commercial fields, such as high-performance motors, brushless DC motors, magnetic separators, magnetic resonance imaging (MRI), sensors, loudspeakers, consumer electronics and green energy.
What Can You Get from SDM Magnetics?
- Steady premium quality.
- Reliable & rapid delivery.
- Professional reports provided.
- Rich choice of magnetic material.
- EXW, FCA, CPT, CIP, DAT, DAP, DDP, FOB, CFR, CIF available.
- Customized for shapes, surface treaments, magnetization directions, etc.
Shape Categories of Sintered Neodymium Magnets
Magnetic Properties of Sintered Neodymium Magnets
The grades of sintered Neodymium magnets are commonly defined via letter N + number + letter. The letter N is the abbreviation and stand for the rare earth element Neodymium. The number represents the (BH)max of the magnet in CGS unit “Mega-Gauss Oersted” (MOGe). There are perhaps one or two letters tagged on the end determine the Hcj and maximum operating temperature of the sintered Neodymium magnets. M (middle), H (high), H (high), SH (super high), UH (ultra high), EH (extreme high), and AH (abnormal high) grade should be greater than 14, 17, 20, 25, 30, 35kOe, respectively. Then their maximum operating temperature can reach 100, 120, 150, 180, 200, and 230 degrees Celsius separately.
| Grade |
Remanence Br |
Coercivity Hcb |
Intrinsic Coercivity Hcj |
Max. Energy Product (BH)max |
Max. Working Temperature | ||||
| T | kGs | kA/m | kOe | kA/m | kOe | kJ/m3 | MGOe | ℃ | |
| N30 | 1.08-1.13 | 10.8-11.3 | ≥798 | ≥10.0 | ≥955 | ≥12 | 223-247 | 28-31 | 80 |
| N33 | 1.13-1.17 | 11.3-11.7 | ≥836 | ≥10.5 | ≥955 | ≥12 | 247-271 | 31-34 | 80 |
| N35 | 1.17-1.22 | 11.7-12.2 | ≥868 | ≥10.9 | ≥955 | ≥12 | 263-287 | 33-36 | 80 |
| N38 | 1.22-1.25 | 12.2-12.5 | ≥899 | ≥11.3 | ≥955 | ≥12 | 287-310 | 36-39 | 80 |
| N40 | 1.25-1.28 | 12.5-12.8 | ≥907 | ≥11.4 | ≥955 | ≥12 | 302-326 | 38-41 | 80 |
| N42 | 1.28-1.32 | 12.8-13.2 | ≥915 | ≥11.5 | ≥955 | ≥12 | 318-342 | 40-43 | 80 |
| N45 | 1.32-1.38 | 13.2-13.8 | ≥923 | ≥11.6 | ≥955 | ≥12 | 342-366 | 43-46 | 80 |
| N48 | 1.38-1.42 | 13.8-14.2 | ≥923 | ≥11.6 | ≥955 | ≥12 | 366-390 | 46-49 | 80 |
| N50 | 1.40-1.45 | 14.0-14.5 | ≥796 | ≥10.0 | ≥876 | ≥11 | 382-406 | 48-51 | 80 |
| N52 | 1.43-1.48 | 14.3-14.8 | ≥796 | ≥10.0 | ≥876 | ≥11 | 398-422 | 50-53 | 80 |
| N55 | 1.46-1.52 | 14.6-15.2 | ≥796 | ≥10.0 | ≥876 | ≥11 | 414-430 | 52-54 | 80 |
| N35M | 1.17-1.22 | 11.7-12.2 | ≥868 | ≥10.9 | ≥1114 | ≥14 | 263-287 | 33-36 | 100 |
| N38M | 1.22-1.25 | 12.2-12.5 | ≥899 | ≥11.3 | ≥1114 | ≥14 | 287-310 | 36-39 | 100 |
| N40M | 1.25-1.28 | 12.5-12.8 | ≥923 | ≥11.6 | ≥1114 | ≥14 | 302-326 | 38-41 | 100 |
| N42M | 1.28-1.32 | 12.8-13.2 | ≥955 | ≥12.0 | ≥1114 | ≥14 | 318-342 | 40-43 | 100 |
| N45M | 1.32-1.38 | 13.2-13.8 | ≥995 | ≥12.5 | ≥1114 | ≥14 | 342-366 | 43-46 | 100 |
| N48M | 1.37-1.43 | 13.7-14.3 | ≥1027 | ≥12.9 | ≥1114 | ≥14 | 366-390 | 46-49 | 100 |
| N50M | 1.40-1.45 | 14.0-14.5 | ≥1033 | ≥13.0 | ≥1114 | ≥14 | 382-406 | 48-51 | 100 |
| N52M | 1.43-1.48 | 14.3-14.8 | ≥1050 | ≥13.2 | ≥1114 | ≥14 | 398-422 | 50-53 | 100 |
| N54M | 1.45-1.50 | 14.5-15.0 | ≥1051 | ≥13.2 | ≥1114 | ≥14 | 414-438 | 52-55 | 100 |
| N35H | 1.17-1.22 | 11.7-12.2 | ≥868 | ≥10.9 | ≥1353 | ≥17 | 263-287 | 33-36 | 120 |
| N38H | 1.22-1.25 | 12.2-12.5 | ≥899 | ≥11.3 | ≥1353 | ≥17 | 287-310 | 36-39 | 120 |
| N40H | 1.25-1.28 | 12.5-12.8 | ≥923 | ≥11.6 | ≥1353 | ≥17 | 302-326 | 38-41 | 120 |
| N42H | 1.28-1.32 | 12.8-13.2 | ≥955 | ≥12.0 | ≥1353 | ≥17 | 318-342 | 40-43 | 120 |
| N45H | 1.32-1.36 | 13.2-13.6 | ≥963 | ≥12.1 | ≥1353 | ≥17 | 342-366 | 43-46 | 120 |
| N48H | 1.37-1.43 | 13.7-14.3 | ≥995 | ≥12.5 | ≥1353 | ≥17 | 366-390 | 46-49 | 120 |
| N50H | 1.40-1.45 | 14.0-14.5 | ≥1011 | ≥12.7 | ≥1353 | ≥17 | 382-406 | 48-51 | 120 |
| N52H | 1.43-1.48 | 14.3-14.8 | ≥1027 | ≥12.9 | ≥1353 | ≥17 | 398-422 | 50-53 | 120 |
| N35SH | 1.17-1.22 | 11.7-12.2 | ≥876 | ≥11.0 | ≥1592 | ≥20 | 263-287 | 33-36 | 150 |
| N38SH | 1.22-1.25 | 12.2-12.5 | ≥907 | ≥11.4 | ≥1592 | ≥20 | 287-310 | 36-39 | 150 |
| N40SH | 1.25-1.28 | 12.5-12.8 | ≥939 | ≥11.8 | ≥1592 | ≥20 | 302-326 | 38-41 | 150 |
| N42SH | 1.28-1.32 | 12.8-13.2 | ≥987 | ≥12.4 | ≥1592 | ≥20 | 318-342 | 40-43 | 150 |
| N45SH | 1.32-1.38 | 13.2-13.8 | ≥1003 | ≥12.6 | ≥1592 | ≥20 | 342-366 | 43-46 | 150 |
| N48SH | 1.37-1.43 | 13.7-14.3 | ≥1027 | ≥12.9 | ≥1592 | ≥20 | 366-390 | 46-49 | 150 |
| N50SH | 1.40-1.45 | 14.0-14.5 | ≥1003 | ≥12.6 | ≥1592 | ≥20 | 382-406 | 48-51 | 150 |
| N28UH | 1.04-1.08 | 10.4-10.8 | ≥764 | ≥9.6 | ≥1990 | ≥25 | 207-231 | 26-29 | 180 |
| N30UH | 1.08-1.13 | 10.8-11.3 | ≥812 | ≥10.2 | ≥1990 | ≥25 | 223-247 | 28-31 | 180 |
| N33UH | 1.13-1.17 | 11.3-11.7 | ≥852 | ≥10.7 | ≥1990 | ≥25 | 247-271 | 31-34 | 180 |
| N35UH | 1.17-1.22 | 11.7-12.2 | ≥860 | ≥10.8 | ≥1990 | ≥25 | 263-287 | 33-36 | 180 |
| N38UH | 1.22-1.25 | 12.2-12.5 | ≥876 | ≥11.0 | ≥1990 | ≥25 | 287-310 | 36-39 | 180 |
| N40UH | 1.25-1.28 | 12.5-12.8 | ≥899 | ≥11.3 | ≥1990 | ≥25 | 302-326 | 38-41 | 180 |
| N42UH | 1.28-1.32 | 12.8-13.2 | ≥899 | ≥11.3 | ≥1990 | ≥25 | 318-342 | 40-43 | 180 |
| N45UH | 1.32-1.36 | 13.2-13.6 | ≥908 | ≥11.4 | ≥1990 | ≥25 | 342-366 | 43-46 | 180 |
| N48UH | 1.37-1.43 | 13.7-14.3 | ≥908 | ≥11.4 | ≥1990 | ≥25 | 366-390 | 46-49 | 180 |
| N28EH | 1.04-1.08 | 10.4-10.8 | ≥780 | ≥9.8 | ≥2388 | ≥30 | 207-231 | 26-29 | 200 |
| N30EH | 1.08-1.13 | 10.8-11.3 | ≥812 | ≥10.2 | ≥2388 | ≥30 | 223-247 | 28-31 | 200 |
| N33EH | 1.13-1.17 | 11.3-11.7 | ≥836 | ≥10.5 | ≥2388 | ≥30 | 247-271 | 31-34 | 200 |
| N35EH | 1.17-1.22 | 11.7-12.2 | ≥876 | ≥11.0 | ≥2388 | ≥30 | 263-287 | 33-36 | 200 |
| N38EH | 1.22-1.25 | 12.2-12.5 | ≥899 | ≥11.3 | ≥2388 | ≥30 | 287-310 | 36-39 | 200 |
| N40EH | 1.25-1.28 | 12.5-12.8 | ≥899 | ≥11.3 | ≥2388 | ≥30 | 302-326 | 38-41 | 200 |
| N42EH | 1.28-1.32 | 12.8-13.2 | ≥899 | ≥11.3 | ≥2388 | ≥30 | 318-342 | 40-43 | 200 |
| N45EH | 1.32-1.36 | 13.2-13.6 | ≥899 | ≥11.3 | ≥2388 | ≥30 | 342-366 | 43-46 | 200 |
| N28AH | 1.04-1.08 | 10.4-10.8 | ≥787 | ≥9.9 | ≥2786 | ≥35 | 207-231 | 26-29 | 230 |
| N30AH | 1.08-1.13 | 10.8-11.3 | ≥819 | ≥10.3 | ≥2786 | ≥35 | 223-247 | 28-31 | 230 |
| N33AH | 1.13-1.17 | 11.3-11.7 | ≥843 | ≥10.6 | ≥2786 | ≥35 | 247-271 | 31-34 | 230 |
| N35AH | 1.17-1.22 | 11.7-12.2 | ≥876 | ≥11.0 | ≥2786 | ≥35 | 263-287 | 33-36 | 230 |
| N38AH | 1.22-1.25 | 12.2-12.5 | ≥899 | ≥11.3 | ≥2786 | ≥35 | 287-310 | 36-39 | 230 |
|
|||||||||
| Parameters | Unit | Reference Range | |
| Temperature Coefficient of Br / α(Br) | %/℃ | -0.08 ~ -0.13 | |
| Temperature Coefficient of Hcj/ β(Hcj) | %/℃ | -0.35 ~ -0.80 | |
| Curie Temperature / Tc | ℃ | 310-380 | |
| Recoil Permeability / μrec | – | 1.05 | |
Physical Properties of Sintered Neodymium Magnets
Besides permanent magnetic performance and corrosion resistance, working stability of sintered Neodymium magnets is strongly related to its unique physical properties. In addition to routine density or hardness, physical properties of sintered Neodymium magnet also included mechanical properties, electrical properties, even thermal properties. Mechanical properties are mainly covered compressive strength, tensile strength, and bending strength. These three metrics possess significantly impact on the machinability and long-term performance of sintered Neodymium magnets. Electrical properties of alloy material are generally characterized by electrical resistivity. Sintered Neodymium magnets have relatively lower electrical resistivity and vulnerable to eddy current loss when applied to high-speed rotary machinery. Thermal properties of sintered Neodymium magnets are usually measured by coefficient of thermal expansion. Thermal expansion of sintered Neodymium magnets will positively cause dimension change, then magnets in the magnetic device will generate a certain of stress due to such dimension change if the expansion difference between magnets and assembly material relatively large, hence lead to mechanical damages and magnetic performance deteriorations.
| Items | Parameters | Unit | Reference Range |
| Regular Physical Properties | Density / ρ | g/cm3 | 7.40-7.80 |
| Vickness Hardness / HV | – | 550-650 | |
| Electrical Properties | Electrical Resistivity | μΩ·m | 1.4 |
| Mechanical Properties | Compressive Strength | MPa | 1050 |
| Tensile Strength | MPa | 80 | |
| Bending Strength | MPa | 290 | |
| Thermal Properties | Thermal Conductivity | W/(m·K) | 6-8 |
| Coefficient of Thermal Expansion | 10-6/K | C⊥: -1.5, C∥6.5. |
Surface Treatments of Sintered Neodymium Magnets
Surface protective treatment is the ineluctable procedure for the sintered Neodymium magnets. Nd-rich phase exhibit quite strong oxidation tendency and will form a primary battery system with main phase under humid condition. Finally, Nd-rich phase is corroded and main phase particle peeled from the body gradually. Surface protective treatment of sintered Neodymium magnets is can be divided into wet and dry process. The commonly-used wet process includes electroplating, electrolessplating, electrophoresis, spray coating, and dip coating. Dry process includes physical vapor deposition (PVD) process and chemical vapor deposition (CVD) process.
| Coating |
Thickness (μm) |
Color |
SST (hrs) |
PCT (hrs) |
Characteristics |
| BW-Zn | 4-15 | Bright blue | ≥24 | – | Secondly commonly used single layer coating. Poor anti-corrosion ability. |
| Color-Zn | 4-15 | Shining color | ≥48 | – | Anti-corrosion ability is better than BW-Zn. |
| Ni-Cu-Ni | 5-20 | Bright silver | ≥48 | ≥48 | Most regular used multi-layer coating. Excellent humidity and salt spray resistance. |
| Chemical-Ni | 5-20 | Dark silver | ≥72 | ≥48 | Excellent humidity and salt spray resistance with uniform appearance. |
| Ni-Cu-Ni-Au | 5-20 | Golden | ≥72 | ≥96 | Excellent electrical conductivity and decorative. |
| Ni-Cu-Ni-Ag | 5-20 | Silver | ≥72 | ≥96 | Excellent electrical conductivity and decorative. |
| Ni-Cu-Ni-Sn | 5-20 | Silver | ≥72 | ≥96 | Excellent humidity resistance. |
| Phosphate | 1-3 | Dark grey | – | – | Temporary protection. |
| Aluminum | 2-15 | Bright silver | ≥24 | ≥24 | Noticeable coating. |
| Epoxy resin | 10-30 | Black/Grey | ≥72 | ≥72 | Excellent humidity and salt spray resistance. Superir binding force. |
| Parylene | 5-20 | Colorless | ≥96 | – | Excellent humidity, salt spray, corrosive vapors, and solvents resistance. Free of pore. |
| Everlube | 10-15 | Golden yellow | ≥120 | ≥72 | Excellent humidity resistance. |
| Teflon | 8-15 | Black | ≥24 | ≥24 | High temperature and rub resistance. Self-lubricant and 100% water-proof. |
| Note: anti-corrosion capability of coating is also influenced by the shape and size of magnet. | |||||
Magnetization Directions of Sintered Neodymium Magnets
Magnetization process refers to apply magnetic field along the definite direction of the permanent magnet to saturate the magnet. Different permanent magnet requires unlike magnetic field strength to achieve saturation. As a type of anisotropic magnet, sintered Neodymium magnets have a preferred direction of magnetization and various pole configurations can be realized as long as not conflicting with its own orientation.
Axially Magnetization
Axially Multipole Magnetization
Diametrically Magnetization
Radial Multipole Magnetization
Skewed Magnetization
Radially Magnetization
Manufacturing Process of Sintered Neodymium Magnets
Magnetization process refers to apply magnetic field along the definite direction of the permanent magnet to saturate the magnet. Different permanent magnet requires unlike magnetic field strength to achieve saturation. As a type of anisotropic magnet, sintered Neodymium magnets have a preferred direction of magnetization and various pole configurations can be realized as long as not conflicting with its own orientation.
Weighing
Melting & Strip Casting
Hydrogen Decrepitation
Jet Milling
Compacting
Sintering
Machining
Surface Treatment
Magnetization
Packaging & Shipping
Influencing Factors of Sintered Neodymium Magnet Price
As a primary raw material, the content of PrNd mischmetal in sintered Neodymium magnets is around 30wt%, therefore, fluctuations of PrNd price trend have the most direct influence on the price of sintered Neodymium magnets. Either Dy or Tb can significantly enhance intrinsic coercivity Hcj of sintered Neodymium magnets, but the cost is sharply increasing at the same time.