Sintered Neodymium Magnets

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, 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.

Sinterd Neodymium Magnets-Main

Manufacturing Process of Sintered Neodymium Magnets

Sintered Neodymium Magnets-Manufacturing Process

Magnetic Properties of Sintered Neodymium Magnets

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
  • The above-mentioned data of magnetic properties and physical properties are given at room temperature.
  • The max working temperature of magnet is changeable due to length-diameter ratio, coating thickness and other environment factors.

Other Properties of Sintered Neodymium Magnets

Items Parameters Unit Reference Range
Other Magnetic Properties Temper. Coeff. of Br / α(Br) %/℃ -0.08 ~ -0.13
Temper. Coeff. of Br / β(Hcj) %/℃ -0.35 ~ -0.80
Curie Temperature / Tc 310-380
Recoil Permeability / μrec 1.05
Physical Properties Density / ρ g/cm3 7.40-7.80
Vickness Hardness / HV 550-650
Electrical Resistivity μΩ·m 1.4
Compressive Strength MPa 1050
Tensile Strength MPa 80
Bending Strength MPa 290
Thermal Conductivity W/(m·K) 6-8
Coeff. of Thermal Expansion 10-6/K C⊥: -1.5, C∥6.5.

Surface Treatment of Sintered Neodymium Magnets

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.
Black-Ni 5-20 Gloss black ≥48 ≥48 Excellent humidity and salt spray resistance with superior appearance and decoration.
Ni + Au 5-20 Golden ≥72 ≥96 Excellent electrical conductivity and decorative.
Ni + Ag 5-20 Silver ≥72 ≥96 Excellent electrical conductivity and decorative.
Ni-Cu-Ni-Sn 5-20 Silver ≥72 ≥96 Excellent humidity resistance.
Passivation/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.

Sintered Neodymium Magnets-surface treatment