NdFeB Magnets Technical Information

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NdFeB Magnets

Neodymium Iron Boron magnets, popularly named Neodymium Magnets, NdFeB magnets or NIB Magnets are one kind of rare earth magnets with excellent Energy Product and high Coercive Force. There are sintered NdFeB magnets and bonded NdFeB magnets. Each with distinct manufacturing processes, physical properties, and application areas.

1. Sintered NdFeB Magnetic Properties

1.1 Sintered NdFeB Magnetic Properties and Grade list ;

1.2 Sintered NdFeB magnets grade list with low reversible temperature coefficient.

1.3 Demagnetization curves at various temperatures of sintered NdFeB motor magnets.

2. Max Dimension and Tolerance of Sintered NdFeB Magnets

2.1 Sintered NdFeB Magnets Shape Type and its Max Dimension

2.2 General Tolerance for sintered NdFeB Magnets in different process

2.3 Geometric Tolerance for sintered NdFeB Magnets in different process

3. Coating of Sintered NdFeB Magnets

4. Mechanical and physical properties of sintered NdFeB Magnets

5. The process for Sintered NdFeB Magnets

6. Bonded NdFeB Magnetic Properties

7. Bonded NdFeB core competition

8. Comparison between sintered NdFeB magnets and Bonded NdFeB Magnets

1. Sintered NdFeB Magnetic Properties

1.1 Sintered NdFeB Magnetic Properties list :

Properties		Remanence(Br)				Coercive force(Hcb)				Intrinsic coercive force(Hcj)		Maximum energy product (BH)max				Working temp
Unit		kGs		T		kOe		kA/m				MGOe		kJ/m3		Working temp
Unit		Nom.	Min.	Nom.	Min.	Nom.	Min.	Nom.	Min.			Nom.	Min.	Nom.	Min.
No	Grade	Nom.	Min.	Nom.	Min.	Nom.	Min.	Nom.	Min.	kOe	kA/m	Nom.	Min.	Nom.	Min.	℃
1	N30	11.2	10.8	1.12	1.08	10.5	10	836	796	≥12	≥955	30	28	239	223	≤80
2	N35	12	11.7	1.2	1.17	11.3	10.8	900	860	≥12	≥955	35	33	279	263	≤80
3	N38	12.6	12.2	1.26	1.22	11.5	11.3	915	900	≥12	≥955	38	36	303	287	≤80
4	N40	12.9	12.6	1.29	1.26	11.6	11.4	924	908	≥12	≥955	40	38	318	303	≤80
5	N42	13.1	12.9	1.31	1.29	11.8	11.5	939	915	≥12	≥955	42	40	342	326	≤80
6	N45	13.6	13.3	1.36	1.33	12	11.6	955	924	≥12	≥955	45	43	358	342	≤80
7	N48	14	13.8	1.4	1.38	10.8	10.2	860	810	≥11	≥875	48	46	383	367	≤80
8	N50	14.3	14.1	1.43	1.41	10.8	10	860	794	≥11	≥875	50	48	398	383	≤80
9	N52	14.5	14.2	1.45	1.42	10.8	10	860	794	≥11	≥875	52	50	414	398	≤60
10	N54	15.1	14.5	1.51	1.45	10.5	10	836	794	≥11	≥875	54	51	429	406	≤60
11	N55	15.4	14.7	1.54	1.47	10.5	10	836	794	≥11	≥875	55	52	438	414	≤60
12	N30M	11.2	10.8	1.12	1.08	10.5	10	836	794	≥14	≥1114	30	28	239	223	≤100
13	N35M	12	11.7	1.2	1.17	11.3	10.9	900	868	≥14	≥1114	35	33	279	263	≤100
14	N38M	12.6	12.2	1.26	1.22	11.8	11.3	939	900	≥14	≥1114	38	36	303	287	≤100
15	N40M	12.9	12.6	1.29	1.26	12	11.6	955	924	≥14	≥1114	40	38	318	303	≤100
16	N42M	13.2	12.9	1.32	1.29	12.4	12	987	955	≥14	≥1114	42	40	342	326	≤100
17	N45M	13.5	13.3	1.35	1.33	12.6	12.2	1003	971	≥14	≥1114	45	43	358	342	≤100
18	N48M	14	13.8	1.4	1.38	13.3	12.9	1059	1027	≥14	≥1114	48	46	383	367	≤100
19	N50M	14.3	14	1.43	1.4	13.5	13.1	1074	1042	≥14	≥1114	50	48	398	383	≤100
20	N52M	14.5	14.2	1.45	1.42	13.6	13.2	1082	1050	≥14	≥1114	52	50	414	398	≤80
21	N30H	11.2	10.8	1.12	1.08	10.5	10	836	794	≥17	≥1353	30	28	239	223	≤120
22	N33H	11.7	11.4	1.17	1.14	11	10.5	876	836	≥17	≥1353	33	31	263	247	≤120
23	N35H	12	11.7	1.2	1.17	11.3	10.9	900	868	≥17	≥1353	35	33	279	263	≤120
24	N38H	12.6	12.2	1.26	1.22	11.8	11.3	939	900	≥17	≥1353	38	36	303	287	≤120
25	N40H	12.8	12.6	1.28	1.26	12	11.6	955	924	≥17	≥1353	40	38	318	303	≤120
26	N42H	13	12.8	1.3	1.28	12.4	12	987	955	≥17	≥1353	42	40	342	326	≤120
27	N45H	13.5	13.3	1.35	1.33	12.6	12.2	1003	971	≥17	≥1353	45	43	358	342	≤120
28	N48H	14	13.8	1.4	1.38	13.3	12.9	1059	1027	≥17	≥1353	48	46	383	367	≤120
29	N50H	14.3	14	1.43	1.4	13.5	13.1	1074	1042	≥17	≥1353	50	48	398	383	≤120
30	N52H	14.5	14.2	1.45	1.42	13.6	13.2	1082	1050	≥17	≥1353	52	50	414	398	≤100
31	N30SH	11.2	10.8	1.12	1.08	10.5	10.1	836	804	≥20	≥1595	30	28	239	223	≤150
32	N33SH	11.7	11.4	1.17	1.14	11	10.6	876	844	≥20	≥1595	33	31	263	247	≤150
33	N35SH	12	11.7	1.2	1.17	11.3	11	900	876	≥20	≥1595	35	33	279	263	≤150
34	N37SH	12.3	12	1.23	1.2	11.5	11.3	915	900	≥20	≥1595	37	35	295	279	≤150
35	N38SH	12.5	12.2	1.25	1.22	11.8	11.4	939	908	≥20	≥1595	38	36	303	287	≤150
36	N40SH	12.7	12.5	1.27	1.25	12.1	11.8	963	939	≥20	≥1595	40	38	318	303	≤150
37	N42SH	13	12.8	1.3	1.28	12.4	12	987	955	≥20	≥1595	42	40	342	326	≤150
38	N45SH	13.5	13.3	1.35	1.33	12.6	12.2	1003	971	≥20	≥1595	45	43	358	342	≤150
39	N48SH	14	13.8	1.4	1.38	13.3	12.9	1059	1027	≥20	≥1595	48	46	383	367	≤130
40	N50SH	14.2	14	1.42	1.4	13.5	13.1	1074	1042	≥20	≥1595	50	48	398	383	≤130
41	N25UH	10	9.6	1	0.96	9.6	9.2	764	732	≥25	≥1990	25	22	199	175	≤180
42	N28UH	10.8	10.4	1.08	1.04	10.2	9.8	812	780	≥25	≥1990	28	26	223	207	≤180
43	N30UH	11.2	10.8	1.12	1.08	10.6	10.1	844	804	≥25	≥1990	30	28	239	223	≤180
44	N33UH	11.5	11.3	1.15	1.13	11	10.6	876	844	≥25	≥1990	33	31	263	247	≤180
45	N35UH	11.9	11.7	1.19	1.17	11.3	11	900	876	≥25	≥1990	35	33	279	263	≤180
46	N38UH	12.5	12.2	1.25	1.22	11.8	11.4	939	908	≥25	≥1990	38	36	303	287	≤180
47	N40UH	12.7	12.5	1.27	1.25	12.2	11.8	971	939	≥25	≥1990	40	38	318	303	≤180
48	N42UH	13	12.8	1.3	1.28	12.4	12	987	955	≥25	≥1990	42	40	342	326	≤180
49	N45UH	13.5	13.3	1.35	1.33	12.6	12.2	1003	971	≥25	≥1990	45	43	358	342	≤150
50	N48UH	14	13.8	1.4	1.38	13.3	12.9	1059	1027	≥25	≥1990	48	45	383	367	≤150
51	N50UH	14.2	13.9	1.42	1.39	13.5	13.1	1074	1042	≥24	≥1911	50	48	398	383	≤150
52	N28EH	10.8	10.4	1.08	1.04	10.4	9.8	811	780	≥30	≥2388	28	26	223	207	≤200
53	N30EH	11.2	10.8	1.12	1.08	10.6	10.1	844	804	≥30	≥2388	30	28	239	223	≤200
54	N33EH	11.5	11.3	1.15	1.13	11	10.6	876	844	≥30	≥2388	33	31	263	247	≤200
55	N35EH	11.9	11.7	1.19	1.17	11.3	11	900	876	≥30	≥2388	35	33	279	263	≤200
56	N38EH	12.4	12.2	1.24	1.22	11.8	11.4	939	908	≥30	≥2388	38	36	303	287	≤200
57	N40EH	12.7	12.4	1.27	1.24	12.2	11.8	971	939	≥30	≥2388	40	38	318	303	≤200
58	N42EH	13	12.8	1.3	1.28	12.4	12	987	955	≥30	≥2388	42	40	334	318	≤200
59	N45EH	13.5	13.3	1.35	1.33	12.6	12.2	1003	971	≥30	≥2388	45	43	358	342	≤200
60	N48EH	14	13.8	1.38	1.38	13.3	12.9	1059	1027	≥30	≥2388	48	46	383	367	≤200
61	N28AH	10.8	10.4	1.08	1.04	10.4	9.8	811	780	≥33	≥2626	28	26	223	207	≤220
62	N30AH	11.2	10.8	1.12	1.08	10.6	10.1	844	804	≥33	≥2626	30	28	239	223	≤220
63	N33AH	11.5	11.3	1.15	1.13	11	10.6	876	844	≥33	≥2626	33	31	263	247	≤220
64	N35AH	11.9	11.7	1.19	1.17	11.5	11	915	876	≥33	≥2626	35	33	279	263	≤220
65	N38AH	12.4	12.2	1.24	1.22	11.8	11.4	939	908	≥33	≥2626	37	35	294	279	≤220
66	N40AH	12.7	12.4	1.27	1.24	12.1	11.8	971	939	≥33	≥2626	39	37	310	294	≤220
67	N42AH	13	12.8	1.3	1.28	12.4	12	987	955	≥33	≥2626	42	40	334	318	≤220
68	N45AH	13.5	13.3	1.35	1.33	12.6	12.2	1003	971	≥33	≥2626	45	43	358	342	≤220
69	N28TH	10.8	10.4	1.08	1.04	10.4	9.8	811	780	≥40	≥3185	28	26	223	207	≤240
70	N30TH	11.2	10.8	1.12	1.08	10.6	10.1	844	804	≥40	≥3185	30	28	239	223	≤240
71	N33TH	11.5	11.3	1.15	1.13	11	10.6	876	844	≥40	≥3185	33	31	263	247	≤240
72	N35TH	11.9	11.7	1.19	1.17	11.5	11	915	876	≥40	≥3185	35	33	279	263	≤240
73	N38TH	12.4	12.2	1.24	1.22	11.8	11.4	939	908	≥40	≥3185	37	35	294	279	≤240
74	N40TH	12.7	12.4	1.27	1.24	12.1	11.8	971	939	≥40	≥3185	39	37	310	294	≤240
75	N28RH	10.8	10.4	1.08	1.04	10.4	9.8	811	780	≥45	≥3583	28	26	223	207	≤260
76	N30RH	11.2	10.8	1.12	1.08	10.6	10.1	844	804	≥45	≥3583	30	28	239	223	≤260
77	N33RH	11.5	11.3	1.15	1.13	11	10.6	876	844	≥45	≥3583	33	31	263	247	≤260
78	N35RH	11.9	11.7	1.19	1.17	11.5	11	915	876	≥45	≥3583	35	33	279	263	≤260

High Temperature Neodymium Magnets ,such as N35RH Grade max working temperature is about 260degree,which are best choice for high Electric Vehicles motor. Special grade Neodymium magnets with reversible temperature coefficient are available , such as aB from -0.09% to -0.11% ，aHcj from -0.45 to -0.55 instead of common grade with aB from 0.12% to -0.13% ，aHcj from -0.55 to -0.65% .Special Grade magnets means can work more stable in high temperature.

There are other kind of High temperature magnets , such as Alnico magnets have lowest reversible temperature coefficient and can work at temperature up to 600 Celsius degree, but its BHmax( can only up to about 10-12MGOe) is very smaller than Neodymium Magnets (its BHmax is from 30-54MGOe), they are mainly used in various instruments. Most SmCo magnets can working up 300 Celsius Degree and Special high super temperature smco magnets can working up to 550 celsius degree, but its magnetic energy product can only up to 26MGOe , or up to 32MGOe with max working temperature is 300 Celsius degree. They are more brittle than neodymium magnets.

1.2 NdFeB magnets with low reversible temperature coefficient.

1.3 Demagnetization curves at various temperatures for motor magnets.

2. Maximum Dimension and Tolerance of Sintered NdFeB Magnets

2.1 Sintered NdFeB Magnets Shape Type and its Max Dimension

Shape	Picture	Dimenion	Recommended	Maximum
Shape	Picture	Dimenion	Dimension/mm	Dimension/mm
Block		L	≤180	≤ 220
		W	≤120	≤150
		T	≤60	≤80
Cylinder		D	≤150	≤220
Cylinder		T	≤60	≤80
Ring		D	≤120	≤160
		d	≤80	≤100
		T	≤45	≤65
Segment		L	≤180	≤220
		W	≤120	≤150
		T	≤60	≤80
		a	0-180°C

Note 1: Weight limit per piece: ≤5kg for "Recommended dimension"; ≤10kg for "Maximum dimension"

Note 2: The Maximum Dimension may be related with the magnet grade.

2.2 General Tolerance for sintered NdFeB Magnets in different process

2.3 Geometric Tolerance for sintered NdFeB Magnets in different process

3. Coating of Sintered NdFeB Magnets

Type	Coating Type	Color	Thickness(um)	SST(h)	PCT(h)	Salt immersion test	Working temp.(℃)	Characteristic
Metal coating	Blue Zn	Blue/White	4-8	≥48	≥48	N/A	＜160	Regular Protection, Applicable to most products
	Color Zn	Multiple colors	4-8	≥72	≥72	N/A	＜160	Excellent salt spray resistance
	NiCuNi	Silver white	10-20	≥72	≥96	N/A	＜200	Excellent humidity, heat &salt spray resistance
	electroless nickel	Silver white	10-30	≥96	≥72		＜200	Excellent humidity, heat &salt spray resistance
	Sn	Silver white	10-25	≥36	≥48		＜202	Excellent humidity, heat &salt spray resistance
	NiCuNI+Golden	Golden		≥12	≥48			Good Looking
	Al	Silver white	5-25	≥96	≥240	N/A	＜390	Excellent adhesive force, high temperature resistance
Organic coating	Epoxy (electro)	Black/Grey	10-30	≥480	≥96	N/A	＜160
Organic coating	Epoxy (spray)	Black/Grey	10-30	≥480	≥96	N/A	＜180
Multi-layer coating	NiCuNi+Epoxy	Black/Grey	15-45	≥720	≥168	N/A	＜180
Inorganic coating	Phosphate/ Passivated	Grey	＜2	N/A	N/A	1H	＜250	Temporary protection
Inorganic coating	Bluing	Blue	＜2	N/A	N/A	2H	＜250	Temporary protection

· The above data represent the best performance. The actual specification is to be adjusted according to variable product size and shape.

· Muli-layer coatings is a combination of different type of coatings. It’s color, thickness and working temperature may vary from different combinations.

· Test condition of PCT: 121°C, 100% humidity, 2 atms;

· Test condition of HAST: 132"C, 95% humidity, 2.7 atms. HAST is to evaluate the weight loss of magnet after testing, the lower the better.

4. Mechanical and physical properties of sintered NdFeB Magnets

Item	Parameters	Reference Value
Mechanical and physical properties	Density(g/cm3)	7.45～7.70
	Vickers Hardness(Hv)	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
	Young's Modulus(GPa)	160
	Coefficient of Thermal Expansion(C ⊥)	-1.5
	Coefficient of Thermal Expansion(C //)	6.5
Additional magnetic properties	Temp.Coeff.ofBr (α(Br))/(%/K)	-0.08～-0.12
	Temp.Coeff.of Hcj (β(Hcj))/(%/K)	-0.42～-0.70
	Curie Temperature (Tc)/(°C)	310～380
	Recoil Permeability (μrec)/(-)	1.05

5. The Process for Sintered NdFeB Magnets

Preparation of Raw Materials → Strip Casting(SC) → Hydrogen Decrepitation (HD) → Jet Milling → Blending → Orienting and Pressing → Vacuum Sintering → Magnetic Properties Inspection → Machining → Plating → Magnetizing

6. Bonded NdFeB Magnets Properties and Grade list

Grade		BN-1	BN-2	BN-3	BN-4	BN-5	BN-6	BN-7	BN-7H	BN-8	BN-8H	BN-9	BN-10	BN-10H	BN-11	BN-12
Grade		BN-1	BN-2	BN-3	BN-4	BN-5	BN-6	BN-7	BN-7H	BN-8	BN-8H	BN-9	BN-10	BN-10H	BN-11	BN-12
Br	(mT)	290-340	380-420	380-420	460-500	480-530	530-580	610-650	590-630	630-680	600-660	650-690	670-710	640-680	690-730	700-740
Br	(KGs)	2.9-3.4	3.8-4.2	3.8-4.2	4.6-5.0	4.8-5.3	5.3-5.8	6.1-6.5	5.9-6.3	6.3-6.8	6.0-6.6	6.5-6.9	6.7-7.1	6.4-6.8	6.9-7.3	7.0-7.4
Hcb	(KA/m)	150-200	180-240	205-255	230-290	255-320	295-350	350-415	390-440	400-440	380-435	395-440	410-455	435-480	420-475	435-495
Hcb	(KOe)	1.9-2.5	2.3-3.0	2.6-3.2	2.9-3.6	3.2-4.0	3.7-4.4	4.4-5.2	4.9-5.5	5.0-5.5	4.8-5.4	5.0-5.5	5.2-5.7	5.5-6.0	5.3-5.9	5.5-6.2
Hcj	(KA/m)	325-375	330-385	540-585	580-630	590-640	605-655	620-680	1035-1120	675-755	800-960	675-755	675-760	940-1025	675-760	690-815
Hcj	(KOe)	4.1-4.7	4.2-4.8	6.8-7.3	7.3-7.9	7.4-8.0	7.6-8.2	7.8-8.5	13-14	8.5-9.4	10.0-12.0	8.5-9.4	8.5-9.5	11.8-12.8	8.5-9.5	8.7-10.2
(BH)max	(KJ/m3)	14-18	20-24	25-29	31-35	39-43	46-50	60-65	58-63	66-70	62-66	69-73	72-76	70-75	78-82	82-86
(BH)max	(MGOe)	1.8-2.2	2.5-2.9	3.2-3.6	3.9-4.4	4.9-5.4	5.9-6.3	7.6-8.1	7.3-7.9	8.3-8.7	7.8-8.2	8.7-9.1	9.1-9.5	8.9-9.3	9.9-10.3	10.3-10.7
μr	(μH/M)	1.20	1.20	1.20	1.20	1.20	1.20	1.20	1.20	1.20	1.20	1.20	1.20	1.20	1.20	1.20
Average reversible temp coefficient	(%/℃)	-0.11	-0.11	-0.10	-0.10	-0.11	-0.11	-0.12	-0.10	-0.12	-0.10	-0.12	-0.12	-0.10	-0.12	-0.12
Saturation magnetization field	KA/m	≥1600	≥1600	≥1600	≥1600	≥1600	≥1600	≥1600	≥2000	≥1600	≥2000	≥1600	≥1600	≥2000	≥1600	≥1600
Saturation magnetization field	KOe	≥20	≥20	≥20	≥20	≥20	≥20	≥20	≥25	≥20	≥25	≥20	≥20	≥25	≥20	≥20
Max working temp	(℃)	160	160	180	180	160	160	160	180	160	180	160	160	180	160	160
Density	(g/cm3)	5.1-5.3	5.4-5.6	4.8-5.0	5.1-5.3	5.4-5.6	5.7-5.9	5.9-6.1	5.9-6.1	5.9-6.1	5.9-6.1	5.9-6.1	5.9-6.1	5.9-6.1	5.9-6.1	5.9-6.1
Density	(g/cm3)	5.1-5.3	5.4-5.6	4.8-5.0	5.1-5.3	5.4-5.6	5.7-5.9	5.9-6.1	5.9-6.1	5.9-6.1	5.9-6.1	5.9-6.1	5.9-6.1	5.9-6.1	5.9-6.1	5.9-6.1
Note: Parameters can be adjusted according to customer requirements.

7. Bonded NdFeB core competition

Bond magnets with more than 13MGOe. The minimum pole width of magnetization accuracy can reach 0.8mm, and the number of poles on one single magnet can reach more than 2000 poles. We can design and provide a variety of products with complex magnetic circuits and magnet assembly complexly assembled. Magnetic encoders for precision CNC machine tools. Products available for mass production include those with 64 poles, 64+62 poles, 64+3 poles, 82 poles, 102 poles, 124 poles, 162 poles, 192 poles, 242 poles, 326 poles etc.

8. Comparison between sintered NdFeB magnets and Bonded NdFeB Magnets

Manufacturing Process

Bonded NdFeB Magnets: These are made by blending NdFeB powder with a polymer binder, usually epoxy, and then either compression molding or injection molding the mixture into the desired shape. The magnets are then magnetized. This process allows for the production of magnets in complex shapes and sizes but with lower magnetic properties.

Sintered NdFeB Magnets: The production involves melting the raw materials in a furnace, casting them into ingots, pulverizing the ingots into a fine powder, pressing the powder in a magnetic field to align the particles, and then sintering the compacted powder at high temperatures before finishing with machining and magnetization. Sintered NdFeB magnets exhibit higher magnetic properties than bonded magnets but are limited in the complexity of shapes that can be efficiently produced.

Magnetic Properties

Bonded NdFeB Magnets: They typically have lower magnetic performance compared to sintered magnets due to the presence of a non-magnetic binder material and a less dense microstructure. However, they can still offer sufficient performance for many applications.

Sintered NdFeB Magnets: These magnets provide the highest magnetic properties available among all permanent magnets, making them ideal for applications requiring strong magnetic fields.

Physical Properties

Bonded NdFeB Magnets: They are generally more resistant to corrosion than sintered magnets, largely because of the protective nature of the bonding agent. They also tend to be more durable against impacts and less prone to chipping and cracking.

Sintered NdFeB Magnets: While offering superior magnetic strength, they are more brittle and susceptible to corrosion if not properly coated or treated with surface treatments.

Applications

Bonded NdFeB Magnets: Commonly used in automotive sensors, electric motors, consumer electronics, and other applications where complex shapes or precise dimensions are required.

Sintered NdFeB Magnets: Widely used in applications demanding high magnetic strength, such as wind turbine generators, hard disk drives, MRI machines, and electric vehicle motors.

Cost

Bonded NdFeB Magnets: The cost can be lower for bonded magnets, especially for complex shapes, as they require less machining and material waste.

Sintered NdFeB Magnets: Typically, sintered magnets can be more expensive due to the high-energy manufacturing process and the need for machining to achieve the final dimensions. Choosing between bonded and sintered NdFeB magnets depends on the specific requirements of the application, including the necessary magnetic strength, desired shape and size, environmental conditions, and budget constraints.