A brief introduction to NdFeB (neodymium) magnet, “the magnet king”

A brief introduction to NdFeB (neodymium) magnet, the magnet king

 

NdFeB (neodymium magnet), simply speaking, is a kind of magnet, but unlike most of the magnets we see, it’s called “the magnet king” because of its excellent magnetic properties. NdFeB are praseodymium metal, boron iron and other alloys, it is also called magnetic steel. NdFeB contains a large amount of rare earth element neodymium, iron and boron to form the Nd2Fe14B tetragonal crystalline structure. so it is hard and brittle in character.

 

Molecular structure

Characteristics

Because the surface is easy to be oxidized corrosion, NdFe must be coated on the surface. Surface chemical passivation is one of the best solutions. As a kind of rare earth permanent magnet, NdFeB has the advantages of extremely high magnetic energy product, high coercive force, and high energy density at the same time, which is widely used in modern industry and electronic technology. So NdFeB makes it possible for the instruments and meters, electronic motor, magnetization of the magnetic separation equipment to be minimized, lightweighted, thinned.

 

Applications

Neodymium magnets have replaced alnico and ferrite magnets in many of the myriad applications in modern technology where strong permanent magnets are required, because their greater strength allows the use of smaller, lighter magnets for a given application. Some examples are:

  • Head actuators for computer hard disks
  • Mechanical e-cigarette firing switches
  • Locks for doors
  • Loudspeakers and headphones
  • Mobile phone speakers, taptic feedback and auto focus actuators
  • Magnetic bearings and couplings
  • Benchtop NMR spectrometers
    • Electric motors: (Using neodymium magnets in electric motors can reduce their power consumption by half.)
    • Cordless tools
    • Servomotors
    • Lifting and compressor motors
    • Synchronous motors
    • Spindle and stepper motors
    • Electrical power steering
    • Drive motors for hybrid and electric vehicles. The electric motors of each Toyota Prius require one kilogram (2.2 lb) of neodymium.
  • Actuators
  • Electric generators for wind turbines (only those with permanent magnet excitation)
  • Alignment of nanocellulose chiral nematic suspensions to fabricate cellulose nanocrystals films with tuneable specular and off-specular optical response
  • Voice coil
  • Retail media case decouplers[clarification needed]
  • In process industries, powerful neodymium magnets are used to catch foreign bodies and protect product and processes

 

Grades

Neodymium magnets are graded according to their maximum energy product, which relates to the magnetic flux output per unit volume. Higher values indicate stronger magnets. For sintered NdFeB magnets, there is a widely recognized international classification. Their values range from 28 up to 52. The first letter N before the values is short for neodymium, meaning sintered NdFeB magnets. Letters following the values indicate intrinsic coercivity and maximum operating temperatures (positively correlated with the Curie temperature), which range from default (up to 80 ℃ or 176 ℉) to AH (230℃ or 446 ℉).

Grades of sintered NdFeB magnets:

N30 – N52

N30M – N50M

N30H – N50H

N30SH – N48SH

N30UH – N42UH

N28EH – N40EH

N28AH – N35AH

Magnetic properties of various grades of NdFeB materials

Material Remanence (minimum) Coercivity (minimum) Coercivity (minimum) Maximum Magnetic Energy Product Density Temperature Coefficient Curie Maximum Service Temperature Recoil
Temperature Permeability
Grade Br Hcj Hcb (BH)max D αBr αHcj Tc Tw μrec
Gs mT Oe KA/m Oe KA/m MGOe KJ/m3 g/m3 %/ ℃ %/ ℃
N42 12800~13300 1280~1330 12000 955 11600 923 40~43 318~342 7.5 -0.12 -0.6 320 80 1.05
N45 13300~13700 1330~1370 12000 955 11000 876 43~46 342~366 7.5 -0.12 -0.6 320 80 1.05
N48 13700~14200 1370~1420 12000 955 11200 892 46~49 366~390 7.5 -0.12 -0.6 320 80 1.05
N50 13900~14400 1390~1440 11000 876.00 10500 836.00 47~51 374~406 7.55 -0.12 -0.6 320 80 1.05
N52 14200~14700 1420~1470 11000 876.00 10500 836.00 49~53 390~422 7.55 -0.12 -0.6 320 80 1.05
N42M 12800~13300 1280~1320 14000 1114.00 12000 955.00 40~43 318~342 7.5 -0.12 -0.6 320 100 1.05
N45M 13300~13700 1330~1370 14000 1114.00 12500 995.00 43~46 342~366 7.5 -0.12 -0.6 320 100 1.05
N48M 13600~14200 1360~1420 14000 1114.00 12800 1019.00 45~49 358~390 7.55 -0.12 -0.6 320 100 1.05
N50M 13900~14400 1390~1440 14000 1114.00 13000 1035.00 47~51 374~406 7.55 -0.12 -0.6 320 100 1.05
N52M 14200~14700 1420~1470 13000 1035.00 12500 995.00 49~53 390~422 7.55 -0.12 -0.6 320 100 1.05
N42H 12800~13300 1280~1330 17000 1353.00 12000 955.00 40~43 318~342 7.55 -0.12 -0.6 320 120 1.05
N45H 13300~13700 1330~1370 17000 1353.00 12100 963.00 43~46 342~366 7.55 -0.12 -0.6 320 120 1.05
N48H 13600~14200 1360~1420 17000 1353.00 12900 1027.00 45~49 358~390 7.6 -0.12 -0.6 320 120 1.05
N50H 13900~14400 1390~1440 16000 1274.00 13000 1035.00 47~51 374~406 7.6 -0.12 -0.6 320 120 1.05
N42SH 12800~13200 1280~1320 20000 1592.00 12200 971.00 40~43 318~342 7.55 -0.11 -0.55 320 150 1.05
N45SH 13200~13700 1320~1370 20000 1592.00 12300 979.00 43~46 342~366 7.6 -0.11 -0.55 320 150 1.05
N48SH 13600~14200 1360~1420 19000 1512.00 12500 995.00 45~49 358~390 7.6 -0.11 -0.55 320 150 1.05
N28UH 10200~10800 1020~1080 25000 1990.00 9600 764.00 26~29 207~231 7.5 -0.1 -0.51 320 180 1.05
N30UH 10800~11300 1080~1130 25000 1990.00 10200 812.00 28~31 223~247 7.5 -0.1 -0.51 320 180 1.05
N33UH 11300~11700 1130~1170 25000 1990.00 10700 852.00 31~34 247~271 7.55 -0.1 -0.51 320 180 1.05
N35UH 11700~12200 1170~1220 25000 1990.00 10800 860.00 33~36 263~287 7.55 -0.1 -0.51 320 180 1.05
N38UH 12200~12500 1220~1250 25000 1990.00 11000 876.00 36~39 287~310 7.6 -0.1 -0.48 320 180 1.05
N40UH 12500~12800 1250~1280 25000 1990.00 11500 915.00 38~41 302~326 7.6 -0.1 -0.48 320 180 1.05
N42UH 12700~13200 1270~1320 24000 1910.00 12200 971.00 39~43 310~342 7.6 -0.1 -0.48 320 180 1.05
N45UH 13200~13700 1320~1370 24000 1910.00 12300 979.00 43~46 342~366 7.6 -0.1 -0.48 320 180 1.05
N28EH 10400~10900 1040~1090 30000 2388.00 9800 780.00 26~29 207~231 7.6 -0.09 -0.48 320 200 1.05
N30EH 10800~11300 1080~1130 30000 2388.00 10200 812.00 28~31 223~247 7.6 -0.09 -0.48 320 200 1.05
N33EH 11300~11700 1130~1170 30000 2388.00 10300 820.00 31~34 247~271 7.6 -0.09 -0.48 320 200 1.05
N35EH 11700~12200 1170~1220 30000 2388.00 10500 836.00 33~36 263~287 7.6 -0.09 -0.48 320 200 1.05
N38EH 12000~12500 1200~1250 30000 2388.00 11500 915.00 35~39 279~310 7.6 -0.09 -0.48 320 200 1.05
N28AH 10200~10900 1020~1090 34000 2706.00 9800 780.00 25~29 199~231 7.6 -0.09 -0.48 320 240 1.05
N30AH 10700~11300 1070~1130 34000 2706.00 10200 812.00 27~31 215~247 7.6 -0.09 -0.48 320 240 1.05
N33AH 11100~11700 1110~1170 34000 2706.00 10300 820.00 30~34 239~271 7.6 -0.09 -0.48 320 240 1.05
N35AH 11700~12200 1170~1220 34000 2706.00 10500 836.00 32~36 255~287 7.6 -0.09 -0.48 320 240 1.05

The largest deposit and reserve of rare earth is in Bayan’obo mine, Inner Mondolia, China.  Baotou bayan’obo mine is the largest rare earth mine in the world.

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