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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

Nom.

Min.

Nom.

Min.

Nom.

Min.

Nom.

Min.

Nom.

Min.

Nom.

Min.

 

No

Grade

kOe

kA/m

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

Dimension/mm

Dimension/mm

Block

L

≤180

≤ 220

W

≤120

≤150

T

≤60

≤80

Cylinder

D

≤150

≤220

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

 

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

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

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

(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

(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

(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

(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

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

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 fuace, 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.

 

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