Sintered NdFeB Magnets

Sintered NdFeB magnets, i.e. sintered neodymium iron boron magnets, are those permanent magnetic materials based on a Nd-Fe-B tetragonal crystal structure. Sintered NdFeB magnets were invented by M. Sagawa’s team in the early 1980s, they are manufactured through a powder metallurgy process.

Sintered NdFeB magnets contain three basic elements neodymium, iron and boron. The neodymium element can be substituted by a portion of other rare earth elements including praseodymium, dysprosium, terbium, cerium, etc. The iron element can be substituted by a portion of cobalt element to increase the magnets’ Curie temperature Tc, thermal stability and corrosion resistance. In order to control the microstructure and the microchemistry so as to meet required performance, it also adds some doping elements including aluminium, copper, niobium, gallium, etc. For custom NdFeB magnets sintered, controlling the formula is the basic method to obtain required magnet grades.

Due to their outstanding magnetic properties (high remanence Br 1.1-1.5 T, middle high coercivity Hcj 800-3000 kA/m^3 and high maximum energy product (BH)max 220-430 kJ/m^3) together with competitive cost, sintered NdFeB magnets are widely applied in DC motors, servo motors, stepper/stepping motors, synchronous motors, linear motors, voice coil motors (VCMs), wind turbines and generators, magnetic resonance imaging (MRI), electric power steering (EPS), magnetic separation, etc.

Sintered NdFeB Magnets’ Grades and Their Magnetic Properties

Grade	B_r		H_cb		H_cj		(BH)_max		T_w
Grade	kGs	T	kOe	kA/m	kOe	kA/m	MGOe	kJ/m³	ºC
N52	14.2-14.8	1.42-1.48	≥10.5	≥836	≥11	≥876	50-53	398-422	≤80
N50	13.9-14.4	1.39-1.44	≥10.8	≥859	≥12	≥955	48-51	382-406
N48	13.6-14.1	1.36-1.41	≥11.6	≥923			46-49	366-390
N45	13.2-13.7	1.32-1.37	≥11.6	≥923			43-46	342-366
N42	12.8-13.3	1.28-1.33	≥11.4	≥907			40-43	318-342
N40	12.4-12.9	1.24-1.29	≥11.4	≥907			38-41	302-326
N38	12.1-12.6	1.21-1.26	≥11.2	≥891			36-39	286-310
N35	11.7-12.2	1.17-1.22	≥10.8	≥859			33-36	263-286
N33	11.3-11.8	1.13-1.18	≥10.5	≥836			31-34	247-271
N30	10.8-11.3	1.08-1.13	≥10.0	≥796			28-31	223-247
N50M	13.9-14.4	1.39-1.44	≥13.0	≥1035	≥13	≥1035	48-51	382-406	≤100
N48M	13.6-14.1	1.36-1.41	≥12.8	≥1019	≥14	≥1114	46-49	366-390
N45M	13.2-13.7	1.32-1.37	≥12.5	≥995			43-46	342-366
N42M	12.8-13.3	1.28-1.33	≥12.0	≥955			40-43	318-342
N40M	12.4-12.9	1.24-1.29	≥11.6	≥923			38-41	302-326
N38M	12.1-12.6	1.21-1.26	≥11.3	≥899			36-39	286-310
N35M	11.7-12.2	1.17-1.22	≥10.9	≥867			33-36	263-286
N33M	11.3-11.8	1.13-1.18	≥10.5	≥836			31-34	247-271
N30M	10.8-11.3	1.08-1.13	≥10.0	≥796			28-31	223-247
N50H	13.9-14.4	1.39-1.44	≥13.0	≥1035	≥16	≥1273	48-51	382-406	≤120
N48H	13.6-14.1	1.36-1.41	≥12.8	≥1019	≥17	≥1353	46-49	366-390
N45H	13.2-13.7	1.32-1.37	≥12.5	≥995			43-46	342-366
N42H	12.8-13.3	1.28-1.33	≥12.0	≥955			40-43	318-342
N40H	12.4-12.9	1.24-1.29	≥11.6	≥923			38-41	302-326
N38H	12.1-12.6	1.21-1.26	≥11.3	≥899			36-39	286-310
N35H	11.7-12.2	1.17-1.22	≥10.9	≥867			33-36	263-286
N33H	11.3-11.8	1.13-1.18	≥10.5	≥836			31-34	247-271
N30H	10.8-11.3	1.08-1.13	≥10.0	≥796			28-31	223-247
N48SH	13.6-14.1	1.36-1.41	≥12.8	≥1019	≥20	≥1592	46-49	366-390	≤150
N45SH	13.2-13.7	1.32-1.37	≥12.5	≥995			43-46	342-366
N42SH	12.8-13.3	1.28-1.33	≥12.0	≥955			40-43	318-342
N40SH	12.4-12.9	1.24-1.29	≥11.6	≥923			38-41	302-326
N38SH	12.1-12.6	1.21-1.26	≥11.3	≥899			36-39	286-310
N35SH	11.7-12.2	1.17-1.22	≥10.9	≥867			33-36	263-286
N33SH	11.3-11.8	1.13-1.18	≥10.5	≥836			31-34	247-271
N30SH	10.8-11.3	1.08-1.13	≥10.0	≥796			28-31	223-247
N42UH	12.8-13.3	1.28-1.33	≥12.2	≥971	≥25	≥1990	40-43	318-342	≤180
N40UH	12.4-12.9	1.24-1.29	≥11.8	≥939			38-41	302-326
N38UH	12.1-12.6	1.21-1.26	≥11.5	≥915			36-39	286-310
N35UH	11.7-12.2	1.17-1.22	≥11.1	≥883			33-36	263-286
N33UH	11.3-11.8	1.13-1.18	≥10.7	≥851			31-34	247-271
N30UH	10.8-11.3	1.08-1.13	≥10.2	≥812			28-31	223-247
N40EH	12.4-12.9	1.24-1.29	≥11.8	≥939	≥30	≥2388	38-41	302-326	≤200
N38EH	12.1-12.6	1.21-1.26	≥11.5	≥915			36-39	286-310
N35EH	11.7-12.2	1.17-1.22	≥11.1	≥883			33-36	263-286
N33EH	11.3-11.8	1.13-1.18	≥10.7	≥851			31-34	247-271
N30EH	10.8-11.3	1.08-1.13	≥10.2	≥812			28-31	223-247
N35AH	11.7-12.2	1.17-1.22	≥11.1	≥883	≥35	≥2786	33-36	263-286	≤230
N33AH	11.3-11.8	1.13-1.18	≥10.7	≥851			31-34	247-271
N30AH	10.8-11.3	1.08-1.13	≥10.2	≥812			28-31	223-247
N28AH	10.4-10.9	1.04-1.09	≥9.8	≥780			26-29	207-231

Note:
∗ The data in the above table were samples’ results tested at the temperature of 20 °C.
∗ The temperature coefficients of Br and Hcj are α(Br): -0.09~-0.12 %/ºC and β(Hcj): -0.40~-0.60 %/ºC, respectively.
∗ The above data are only for reference, magnets can be tailored according to customers’ personalized requirements.

Sintered NdFeB Magnets’ Shapes, Magnetization Direction and Size Range

Shape	Graphic Description	Magnetization Direction		Size Range
Disc/Cylinder Magnet			Axially Magnetized	D: 1-100 mm
				T: 0.5-100 mm
			Diametrically Magnetized	D: 1-100 mm
				T: 0.5-100 mm
Ring Magnet			Axially Magnetized	OD: 4-100 mm
				ID: 1-90 mm
				T: 1-60 mm
			Diametrically Magnetized	OD: 4-100 mm
				ID: 1-90 mm
				T: 1-60 mm
			Radially Magnetized	OD: 24-200 mm
				ID: 18-180 mm
				T: 5-60 mm
Block/Rectangular Magnet			Thickness Magnetized	L: 1-160 mm
				W: 1-100 mm
				T: 1-100 mm
Arc/Segment Magnet			Diametrically Magnetized	OD-ID≥1 mm
				L: 1-160 mm
				W: 3-100 mm
				H: 1-80 mm

Note:
∗ Other shapes of sintered NdFeB magnets can also be tailored according to customers’ specific requirements.

Sintered NdFeB Magnets' Coatings

Coating	Thickness (μm)	SST (hr)	PCT (hr)	T_w (ºC)
Zn (Zinc)	5-15	>24	-	≤160
C-Zn (Colored Zinc)	5-15	>48	-	≤160
Electroless Nickel	10-30	>96	>72	≤230
NiCuNi (Nickel Copper Nickel)	10-20	>48	>48	≤230
NiCu + Black Nickel	10-20	>48	>72	≤230
NiCuNi + Tin	10-25	>48	>48	≤160
NiCuNi + Gold	10-25	>48	>48	≤230
NiCuNi + Silver	10-25	>48	>48	≤160
Epoxy	10-30	>72	>48	≤160
Teflon	10-20	>48	-	≤230
Everlube	10-20	>96	>72	≤230
Parylene	0.2-5	>96	-	≤230

Note:
∗ Salt spray test (SST) was conducted at 35 ºC with 5% NaCl solution.
∗ Pressure cooker test (PCT) was conducted at 120 ºC, 2 atm and 100% RH.

Sintered NdFeB Magnets Physical Properties

Parameter	Unit	Value
Density (ρ)	g/cm³	7.4-7.7
Curie Temperature (T_c)	ºC	310-370
Recoil Permeability (μ_rec)	-	1.05
Vickers Hardness (HV)	MPa	500-600
Bending Strength (σ_bb)	MPa	200-400
Compressive Strenght (σ_bc)	MPa	1000-1100
Tensile Strength (σ_b)	MPa	80-90
Resistivity (ρ)	μΩ·m	1.4-1.6
Thermal Conductivity (λ)	W/(m·K)	8-10
Young's Modulus (E)	GPa	150-200
Thermal Expansivity ∥ Magnetization (α_∥)	10^-6/ºC	3-4
Thermal Expansivity ⊥ Magnetization (α_⊥)	10^-6/ºC	1-3

Note:
∗ The above data are only for reference, specific magnets maybe have different values.

Sintered NdFeB Magnets’ Grades and Their Magnetic Properties

Sintered NdFeB Magnets’ Shapes, Magnetization Direction and Size Range

Sintered NdFeB Magnets' Coatings

Sintered NdFeB Magnets Physical Properties

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