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Neodymium Magnets: A Comprehensive Guide to Properties, Manufacturing Process, Applications, and More - Your Ultimate Resource

Table of Contents

Geometry of Neodymium Magnets

Neodymium magnets, also known as NdFeB magnets or neo magnets, are the third generation of rare earth magnet developed in early 1980s independently by General Motors and Sumitomo Special Metals. According to manufacturing process, they can be divided into sintered neodymium magnets, bonded neodymium magnets, and hot-pressed neodymium magnets. Sintered neodymium magnets have the highest energy product among all types of permanent magnets.

neodymium ring magnet
ring magnet
neodymium disc magnet
disc magnet
neodymium cylinder magnet
cylinder magnet
neodymium square magnet
square magnet
neodymium rectangular magnet
rectangular magnet
neodymium bar magnet
bar magnet
arc motor magnets
arc motor magnets
neodymium wedge magnet
wedge magnet
countersunk neodymium magnet
countersunk magnet
neodymium sphere magnets
sphere magnets

Grade of Neodymium Magnets

According to remanence (Br) and coercivity (Hc), the grade of sintered neodymium magnets can vary in two ways. Take N42UH grade as an example, N represents Neodymium, 42 remanence, and UH coercivity (resistance to demagnetization). Generally, the magnet grade can range from N27 to N55 in the perspective of remanence, N to TH in the perspective of coercivity or resistance to demagnetization. There is a wide range of neodymium magnet grades available, each suited for different applications, primarily based on the needed field strength and operating temperature.

Grade Remanence
(Br)
Intrinsic Coercivity
(Hcj)
Coercivity
(Hcb)
Maximum Energy Product
(BH)max
Temperature  Coeffcient
(α)
Max.Working Temp.
T kGs kA/m kOe kA/m kOe kJ/m3 MGOe αBr αHcj °C
Max Min Max Min Min Min Min Min Max Min Max Min %/℃ %/℃ (L/D=0.7)

 

N54 1.50 1.45 15.0 14.5 876 11 836 10.5 437 414 55 52 -0.12 -0.76 60 140
N52 1.47 1.42 14.7 14.2 876 11 836 10.5 422 390 53 49 -0.12 -0.76 80 176
N50 1.44 1.39 14.4 13.9 955 12 860 10.8 406 374 51 47 -0.12 -0.76 80 176
N48 1.42 1.37 14.2 13.7 955 12 860 10.8 390 358 49 45 -0.12 -0.76 80 176
N45 1.37 1.32 13.7 13.2 955 12 899 11.3 366 342 46 43 -0.12 -0.76 80 176
N42 1.32 1.28 13.2 12.8 955 12 899 11.3 342 318 43 40 -0.12 -0.76 80 176
N40 1.28 1.25 12.8 12.5 955 12 899 11.3 326 302 41 38 -0.12 -0.76 80 176
N38 1.25 1.22 12.5 12.3 955 12 899 11.3 310 287 39 36 -0.12 -0.76 80 176
N35 1.22 1.17 12.2 11.7 955 12 860 10.8 287 263 36 33 -0.12 -0.76 80 176
N33 1.17 1.13 11.7 11.3 955 12 836 10.5 271 247 34 31 -0.12 -0.76 80 176
N30 1.13 1.08 11.3 10.8 955 12 796 10.0 247 223 31 28 -0.12 -0.76 80 176
N52M 1.47 1.42 14.7 14.2 1114 14 1035 13.0 422 390 53 49 -0.12 -0.68 100 212
N50M 1.44 1.39 14.4 13.9 1114 14 1035 13.0 406 374 51 47 -0.12 -0.68 100 212
N48M 1.42 1.36 14.2 13.6 1114 14 1027 12.9 390 358 49 45 -0.12 -0.68 100 212
N45M 1.37 1.32 13.7 13.2 1114 14 995 12.5 366 342 46 43 -0.12 -0.68 100 212
N42M 1.32 1.28 13.2 12.8 1114 14 955 12.0 342 318 43 40 -0.12 -0.68 100 212
N40M 1.28 1.25 12.8 12.5 1114 14 923 11.6 326 302 41 38 -0.12 -0.68 100 212
N38M 1.25 1.22 12.5 12.3 1114 14 899 11.3 310 287 39 36 -0.12 -0.68 100 212
N35M 1.22 1.17 12.2 11.7 1114 14 868 10.9 287 263 36 33 -0.12 -0.68 100 212
N33M 1.17 1.13 11.7 11.3 1114 14 836 10.5 271 247 34 31 -0.12 -0.68 100 212
N30M 1.13 1.08 11.3 10.8 1114 14 796 10.0 247 223 31 28 -0.12 -0.68 100 212
N52H 1.47 1.42 14.7 14.2 1274 16 1043 13.1 422 390 53 49 -0.12 -0.66 120 248
N50H 1.44 1.39 14.4 13.9 1353 17 1035 13.0 406 374 51 47 -0.12 -0.66 120 248
N48H 1.42 1.36 14.2 13.6 1353 17 1027 12.9 390 358 49 45 -0.12 -0.66 120 248
N45H 1.37 1.32 13.7 13.2 1353 17 995 12.5 366 342 46 43 -0.12 -0.66 120 248
N42H 1.32 1.28 13.2 12.8 1353 17 955 12.0 342 318 43 40 -0.12 -0.66 120 248
N40H 1.28 1.25 12.8 12.5 1353 17 923 11.6 326 302 41 38 -0.12 -0.66 120 248
N38H 1.25 1.22 12.5 12.3 1353 17 899 11.3 310 287 39 36 -0.12 -0.66 120 248
N35H 1.22 1.17 12.2 11.7 1353 17 868 10.9 287 263 36 33 -0.12 -0.66 120 248
N33H 1.17 1.13 11.7 11.3 1353 17 836 10.5 271 247 34 31 -0.12 -0.66 120 248
N30H 1.13 1.08 11.3 10.8 1353 17 796 10 247 223 31 28 -0.12 -0.66 120 248
N52SH 1.44 1.42 14.4 14.2 1592 20 1076 13.5 422 390 53 49 -0.12 -0.66 140 284
N50SH 1.42 1.39 14.2 13.9 1592 20 1053 13.2 406 374 51 47 -0.12 -0.66 140 284
N48SH 1.40 1.36 14.0 13.6 1592 20 1035 13.0 390 358 49 45 -0.11 -0.56 150 302
N45SH 1.37 1.32 13.7 13.2 1592 20 995 12.5 366 342 46 43 -0.11 -0.56 150 302
N42SH 1.32 1.28 13.2 12.8 1592 20 955 12.0 342 318 43 40 -0.11 -0.56 150 302
N40SH 1.28 1.25 12.8 12.5 1592 20 939 11.8 326 302 41 38 -0.11 -0.56 150 302
N38SH 1.25 1.22 12.5 12.2 1592 20 907 11.4 310 287 39 36 -0.11 -0.56 150 302
N35SH 1.22 1.17 12.2 11.7 1592 20 876 11.0 287 263 36 33 -0.11 -0.56 150 302
N33SH 1.17 1.13 11.7 11.3 1592 20 844 10.6 271 247 34 31 -0.11 -0.56 150 302
N30SH 1.13 1.08 11.3 10.8 1592 20 804 10.1 247 223 31 28 -0.11 -0.56 150 302
N28SH 1.09 1.04 10.9 10.4 1592 20 788 9.9 223 199 29 25 -0.11 -0.56 150 302
N50SHT 1.42 1.39 14.2 13.9 1751 22 1053 13.2 406 374 51 47 -0.11 -0.56 150 302
N48SHT 1.40 1.36 14 13.6 1751 22 1031 12.9 390 358 49 45 -0.11 -0.56 160 320
N45SHT 1.37 1.32 13.7 13.2 1751 22 1003 12.6 366 342 46 43 -0.11 -0.56 160 320
N42SHT 1.32 1.28 13.2 12.8 1751 22 971 12.2 342 318 43 40 -0.11 -0.53 160 320
N40SHT 1.28 1.25 12.8 12.5 1751 22 947 11.9 326 302 41 38 -0.11 -0.53 160 320
N38SHT 1.25 1.22 12.5 12.2 1751 22 923 11.6 310 287 39 36 -0.11 -0.53 160 320
N35SHT 1.22 1.17 12.2 11.7 1751 22 884 11.1 287 263 36 33 -0.11 -0.53 160 320
N33SHT 1.17 1.13 11.7 11.3 1751 22 860 10.8 271 247 34 31 -0.11 -0.53 160 320
N30SHT 1.13 1.08 11.3 10.8 1751 22 812 10.2 247 223 31 28 -0.11 -0.53 160 320
N50UH 1.42 1.39 14.2 13.9 1990 25 1053 13.2 406 374 51 47 -0.11 -0.53 170 338
N48UH 1.40 1.36 14.0 13.6 1990 25 1031 12.9 390 358 49 45 -0.11 -0.53 180 356
N45UH 1.36 1.32 13.6 13.2 1990 25 1003 12.6 366 342 46 43 -0.11 -0.50 180 356
N42UH 1.32 1.28 13.2 12.8 1990 25 971 12.2 342 318 43 40 -0.10 -0.50 180 356
N40UH 1.28 1.25 12.8 12.5 1990 25 923 11.6 326 302 41 38 -0.10 -0.50 180 356
N38UH 1.25 1.22 12.5 12.2 1990 25 907 11.4 310 287 39 36 -0.10 -0.50 180 356
N35UH 1.22 1.17 12.2 11.7 1990 25 860 10.8 287 263 36 33 -0.10 -0.50 180 356
N33UH 1.17 1.13 11.7 11.3 1990 25 852 10.7 271 247 34 31 -0.10 -0.50 180 356
N30UH 1.13 1.08 11.3 10.8 1990 25 812 10.2 247 223 31 28 -0.10 -0.50 180 356
N48VH 1.40 1.36 14.0 13.6 2149 27 1031 12.9 390 358 49 45 -0.10 -0.50 180 356
N45VH 1.36 1.32 13.6 13.2 2149 27 1003 12.6 366 342 46 43 -0.10 -0.50 190 374
N42VH 1.32 1.28 13.2 12.8 2149 27 971 12.2 342 318 43 40 -0.10 -0.50 190 374
N40VH 1.28 1.25 12.8 12.5 2149 27 947 11.9 326 302 41 38 -0.10 -0.50 190 374
N38VH 1.25 1.22 12.5 12.2 2149 27 923 11.6 310 287 39 36 -0.10 -0.50 190 374
N35VH 1.22 1.17 12.2 11.7 2149 27 884 11.1 287 263 36 33 -0.10 -0.50 190 374
N33VH 1.17 1.13 11.7 11.3 2149 27 860 10.8 271 247 34 31 -0.10 -0.50 190 374
N30VH 1.13 1.08 11.3 10.8 2149 27 852 10.7 247 223 31 28 -0.10 -0.50 190 374
N48EH 1.35 1.40 13.5 14 2388 30 1051 13.2 390 358 49 45 -0.10 -0.45 200 392
N45EH 1.36 1.32 13.6 13.2 2388 30 1031 12.9 366 342 46 43 -0.10 -0.45 200 392
N42EH 1.32 1.28 13.2 12.8 2388 30 970 12.2 342 318 43 40 -0.10 -0.45 200 392
N40EH 1.28 1.25 12.8 12.5 2388 30 947 11.9 326 302 41 38 -0.10 -0.45 200 392
N38EH 1.25 1.22 12.5 12.2 2388 30 915 11.5 310 287 39 36 -0.10 -0.45 200 392
N35EH 1.22 1.17 12.2 11.7 2388 30 884 11.1 287 263 36 33 -0.10 -0.45 200 392
N33EH 1.17 1.13 11.7 11.3 2388 30 860 10.8 271 247 34 31 -0.10 -0.45 200 392
N30EH 1.13 1.08 11.3 10.8 2388 30 820 10.3 247 223 31 28 -0.10 -0.45 200 392
N45FH 1.36 1.32 13.6 13.2 2547 32 1031 12.9 366 342 46 43 -0.10 -0.45 210 410
N42FH 1.32 1.28 13.2 12.8 2547 32 970 12.2 342 318 43 40 -0.10 -0.45 210 410
N40FH 1.28 1.25 12.8 12.5 2547 32 947 11.9 326 302 41 38 -0.10 -0.45 210 410
N38FH 1.25 1.22 12.5 12.2 2547 32 915 11.5 310 287 39 36 -0.10 -0.45 210 410
N35FH 1.22 1.17 12.2 11.7 2547 32 884 11.1 287 263 36 33 -0.10 -0.45 210 410
N33FH 1.17 1.13 11.7 11.3 2547 32 860 10.8 271 247 34 31 -0.10 -0.45 210 410
N30FH 1.13 1.08 11.3 10.8 2547 32 820 10.3 247 223 31 28 -0.10 -0.45 210 410
N42AH 1.32 1.28 13.2 12.8 2786 35 970 12.2 342 318 43 40 -0.10 -0.45 230 446
N40AH 1.28 1.25 12.8 12.5 2786 35 947 11.9 326 302 41 38 -0.10 -0.45 230 446
N38AH 1.25 1.22 12.5 12.2 2786 35 915 11.5 310 287 39 36 -0.10 -0.45 230 446
N35AH 1.20 1.17 12.0 11.7 2786 35 883 11.1 287 263 36 33 -0.10 -0.45 230 446
N33AH 1.17 1.11 11.7 11.1 2786 35 844 10.6 271 239 34 31 -0.10 -0.45 230 446
N30AH 1.13 1.07 11.3 10.7 2786 35 812 10.2 247 215 31 27 -0.10 -0.45 230 446
N28AH 1.09 1.02 10.9 10.2 2786 35 772 9.7 231 199 29 25 -0.10 -0.45 230 446
N38TH 1.25 1.22 12.5 12.2 3182 40 915 11.5 310 287 39 36 -0.10 -0.42 260 500
N35TH 1.22 1.17 12.2 11.7 3182 40 867 10.9 287 263 36 33 -0.10 -0.42 260 500
N33TH 1.17 1.11 11.7 11.1 3182 40 851 10.7 271 239 34 31 -0.10 -0.42 260 500
N30TH 1.13 1.08 11.3 10.8 3182 40 820 10.3 247 223 31 28 -0.10 -0.42 260 500

Coating (surface treatment)​

Coating Abbreviation color thickness
(µm)
corrosion resistance (rating 1 to 10) Surface Tension (γ)
SST HHT PCT
   Nickel (barrel)   NiCuNi   Bright silver 5-20 5 5 5 36
   Nickel (rack)   NiCuNi   Bright silver 5-20 4 5 5 36
   3+Cr Zinc (barrel)   Zn   Blue&white 4-15 4 3 3 38
   3+Cr Zinc (rack)   Zn   Blue&white 4-15 3 3 3 38
   3+Cr Color Zinc (barrel)   Colored Zn   Bright color 4-15 3 3 3 38
   3+Cr Color Zinc (rack)   Colored Zn   Bright color 4-15 3 3 3 38
   Electroless nickel plating   (barrel)   Electroless Ni   Dark silver 3-20 5 5 4 36
   Electroless nickel plating (rack)   Electroless Ni   Dark silver 3-20 4 5 4 36
   Nickel+Chromium   Cr   Dark black 5-20 4 5 5 36
   Teflon   PTFE   Dark grey 15-65 3 3 3 36
   Nickel+Black Nickel   Black Ni   Black 5-20 5 5 5 36
   Nickel+Tin   Sn   Bright silver 5-20 4 5 5 36
   Nickel+Silver   Ag   Silver 5-20 4 5 5 36
   Nickel+Gold   Au   Golden 5-20 4 5 5 36
   Epoxy   Epoxy   Black 15-65 5 5 4 36
   Nickel+Epoxy   NiCu+Epoxy   Black 25-65 5 5 3 36
   Passivation/Phosphorization   Phosphate   Dark grey 1-3 37
   Nano Coating   Nano   Gray/Black 15-65 6 6 7 33

Manufacturing Process

Sintered neodymium magnet (Neodymium-Iron-Born or Nd-Fe-B) is an alloy consisting of neodymium, iron, boron, cobalt, varying levels of praseodymium, dysprosium or terbium and other transition metals. The manufacturing process for sintered neodymium magnets are divided into two main stages: powder metallurgy and mechanical processing. There are are six critical manufacturing steps involved in the powder metallurgy stage.

Raw material including PrNd alloy, iron, copper, DyFe, etc. are mixed and melted together according to a certain proportion. These are heated in a vacuum furnace and a stream of molten metal is forced under pressure onto a cooled drum where it is rapidly cooled at approximately 100,000 degrees-per-second. As a result, strip cast NdFeB ingot is produced for further processing

After melting and casting, the NdFeB alloy ingot is subject to hydrogen atmosphere. Hydrogen slowly absorbs into the solid alloy and makes it brittle, which upon milling becomes fine powder. The process is therefore called hydrogen decrepitation.

The NdFeB powder produced from hydrogen decrepitation is protected in an inert gas atmosphere and handled in glove boxes before going to the automated press. The powder are then fed into a grinding chamber, where the high-velocity gas streams are introduced to cause particles clash violently against each other. As a result, extremely fine powder having a size ranging from 3 to 5 μm is produced.

The powder from jet milling is pressed. During the pressing, a strong magnetic field is applied in order to rotate the powder particles so that their main crystal axes are aligned. That’s required to achieve anisotropy, which means that every piece of powder in the finished magnet will contribute to the magnetic field. Without the alignment, the c-axis (crystal axis) would be more or less randomly distributed, and only those particles which are roughly in the direction of the magnetization field would be magnetized, resulting in a significantly weaker magnet.

The pressed NdFeB block is bagged and immersed into a cold isostatic press (CIP) under huge pressure. This process intends to remove the remaining air gaps within the block. NdFeB blocks coming out of CIP become a bit smaller than it was before it goes in.

The pressed blocks are placed in a sintering furnace at an extremely high temperature just below the melting point of the NdFeB alloy. At this temperature of over 1000 degree, the individual atoms have a lot of motion, which enables the NdFeb alloy to develop their full magnetic and mechanical properties. The magnetic domains maintain the same orientation they had before sintering. At this temperature, shrinkage of NdFeB blocks takes place and full density is achieved. 

After sintering, there are pent-up stresses in the metal from all the movement during sintering, so the blocks are heat-treated again in a step fashion at lower temperatures to reduce the stresses. The blocks are ramped up to a high holding temperature for a set time and then they are ramped down to a lower holding temperature. Once the holding time is achieved, the now stress-free blocks are slowly cooled to room temperature.

Direction of Magnetization​

Sintered neodymium magnets are anisotropic and can only be magnetized in the predetermined direction. Generally, the magnets are axially magnetized (magnet in round shape) or magnetized through thickness (magnet in square or rectangular shape).

However, it’s not uncommon to find neodymium disc magnets diametrically magnetized, especially when they are used in rotary position sensors. Beyond simple two-pole magnetization, sintered neodymium magnets can also be magnetized in sectors.Examples of different magnetization patterns are given below. (Sinter neodymium magnets in ring shape can have axial, diametrical, or radial magnetization. Arc magnets are usually diametrically magnetized in pair since they are used in electric motors. Thus the name, arc motor magnets.

magnetization patterns tengye magnetic (magnetization direction)

Maximum Working Temperature

Sintered neodymium magnets are characterized by their excellent magnetic performance at room temperature. However, they have the least temperature resistance compared to other permanent magnets. N grade magnet only has a theoretical temperature limit of 80°C. (The practical maximum operating temperature is related to the L/D ratio of the magnet.) 

Temperature Characteristics of sintered NdFeB magnets and Sm2Co17 magnet
NdFeB magnets vs. Sm2Co17 magnets

For higher temperature resistance, high-cost heavy rare earth elements (HREEs) are needed to increase the magnet coercivity. Even with the help of grain boundary diffusion (GBD) technology, less heavy rare earth is needed to increase the coercivity, the cost to produce sintered neodymium magnets that can withstand temperature over 200°C is still very high. That’s why the market for Samarium-Cobalt magnets still widely exists in e.g. aerospace, military industry, etc.

Hitachi Licensed Neodymium Magnets

To avoid future potential litigation, companies who sell their products containing NdFeB magnets in North America or Japan usually require Hitachi licensed neodymium magnets. In China, there are eight Hitachi authorized NdFeB manufacturers in total. Our strategic partnership with some of these authorized NdFeB manufacturers allows us to specially outsource licensed magnets at a reasonable price even in low volume.

Raw Material "NdPr Price" | Neodymium Magnet Price​

Neodymium magnets are known for its high price, but more importantly for its price volatility. Rare earth alloy – NdPr alloy is the determinant of the magnet price change. PrNd alloy is of vital importance to the production and cost of all types of neodymium magnets. It’s also an indictor of price trend of neodymium magnets.

latest NdPr price chart

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FAQ

Do Neodymium Magnets Rust?
Because neodymium magnets contain iron, they are prone to rusting when exposed to moisture and oxygen. To prevent corrosion, neodymium magnets are usually coated with coatings, such as nickel, zinc, epoxy, etc. However, if the protective coating is damaged or if they are exposed to harsh conditions, there is a risk of rusting.

How Strong are Neodymium Magnets?
The strength of a neodymium magnet is often measured in terms of its magnetic energy product. Neodymium magnets typically have a magnetic energy product ranging from about 33 to 52 mega-Gauss-oersteds (MGOe). For detailed information, please look at the table of “Grade of Neodymium Magnets” on this page.

What are Neodymium Magnets Used for?
Some applications of neodymium magnets:
Electric Motors and Generators: electric vehicles, wind turbines, and more.
Audio Devices: speakers, headphones, and microphones for high-quality sound.
Magnetic Fasteners: bags, closures, and jewelry clasps.
Automotive Sensors: speed sensors and ABS systems.
Home Appliances: refrigerator door seals, latches, and small motors.
Magnetic Separators: mining and recycling to separate materials.

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