Bonded magnet appeared around the 1970s, when the SmCo magnets have reached the commercialization. The market situation of sintered permanent magnet is very good, but it is difficult to be machined into special shape, and also prone to cracking and breakage, in the process of falling edge off angle and other issues, also not easy to be assembled, thus the applications were limited. In order to solve this problem, the permanent magnet is crushed, mixed with plastic, and pressed in the magnetic field. This is probably the most original method of manufacturing bonded magnets.
Bonded NdFeB, consisting of Nd2Fe14B, is a kind of synthetic magnet. Bonded NdFeB magnets（also called as bonded neodymium magnets） are widely used because of their low cost, high dimensional accuracy, large form freedom, good mechanical strength and light weight. The annual growth rate is 35%. Since the emergence of NdFeB permanent magnet powder, the flexible bonded magnets have been developed rapidly due to their high magnetic properties.
Bonded NdFeB magnets processed by composing of magnetic powder, mixing, granulating, pressing, curing, finishing, coating, magnetic and packaging production process.The bonded NdFeB magnets can be made in diameter to multipole, radial, multi angle oblique filling, magnetizing axial multipolar etc. And can be machined into various complex shaped products, fine, super Pu, one-time high control precision. The energy product is three times of sintered ferrite magnets, coercivity and high magnetic properties, stability, consistency and good performance. The performance fluctuation in the range of 5%, the maximum working temperature can reach 150 degrees. The product surface coated with epoxy resin and parylene coating, corrosion resistance good, smooth, no bubbles, cracks, spalling Fly away, side, grain and other phenomena.
The advantages of bonded NdFeB magnets: high remanence, high coercivity, high magnetic energy products, high-performance price ratio, easy processing of various sizes and tiny size. Compared with sintered NdFeB magnets, it can be formed at one time without the second processing. It can be made into a magnet of various shapes, which is not comparable to a sintered magnet. By using bonded NdFeB magnets, the volume and weight of the motor can be greatly reduced.
The application field of bonded NdFeB magnets:
Bonded NdFeB magnet is made of NdFeB powder by adding a binder. Its development was quite rapid since successfully developed out in 1988., the yield increased exponentially, it is a kind of high performance permanent magnetic materials, in line with contemporary electronic products short, small, light, thin development trend.
The production and application of the development of bonded NdFeB magnets was late, so the application is not wide, the dosage is small, mainly for office automation equipment, electrical machinery, audio-visual equipment, instrumentation, small motor and mechanical measurement, in the mobile phone, CD-ROM, DVD-ROM motor drive, hard disk spindle motor HDD, other applications of micro DC motor automation and instrumentation and other fields are widely used. The proportion of China's bonded NdFeB magnets in recent years: computer takes up 62%, electronics industry accounts for 7%, office automation equipment accounts for 8%, automobile accounted for 7%, utensil takes up 7% , other 9%.
Performance/Property Parameter of Bonded NdFeB Magnets:
|
Grade
|
Br T(Gs)
|
Hcb
kA/m(kOe)
|
Hcj
kA/m(kOe)
|
(BH)max kJ/m3 (MGOe)
|
Dg/cm 3
|
μr
|
α（ B r ） %/ ℃
|
Tw ℃
|
|
BNP-6
|
0.55-0.62
|
285-370 (3.6-4.6)
|
600-755 (7.5-9.5)
|
44-56 ( 5.5-7)
|
5.5-6.1
|
1.15
|
-0.13
|
100
|
|
BNP-8L
|
0.60-0.64
|
360-400 (4.5-5.0)
|
715-800 (9-10)
|
56-64 (7.0-8.0)
|
5.6-6.1
|
1.15
|
-0.13
|
110
|
|
BNP-8
|
0.62-0.69
|
385-445 (4.8-5.6)
|
640-800 (8-10)
|
64-72 (8.0-9.0)
|
5.8-6.1
|
1.15
|
-0.13
|
120
|
|
BNP-8SR
|
0.62-0.66
|
410-465 (5.2-5.8)
|
880-1120 (11-14)
|
64-72 (8.0-9.0
|
5.8-6.1
|
1.13
|
-0.13
|
150
|
|
BNP-8H
|
0.61-0.65
|
410-455 (5.2-5.7)
|
1190-1440 (15-18)
|
64-72 (8.0-9.0)
|
5.9-6.2
|
1.15
|
-0.07
|
125
|
|
BNP-9
|
0.65-0.70
|
400-440 (5.0-5.5)
|
640-800 (8-10)
|
70-76 (8.8-9.5)
|
5.8-6.1
|
1.22
|
-0.12
|
120
|
|
BNP-10
|
0.68-0.72
|
420-470 (5.3-5.9)
|
640-800 (8-10)
|
76-84 (9.5-10.5)
|
5.8-6.1
|
1.22
|
-0.11
|
120
|
|
BNP-11
|
0.70-0.74
|
445-480 (5.6-6.0)
|
680-800 (8.5-10)
|
80-88 (10.0-11.0)
|
5.8-6.1
|
1.22
|
-0.11
|
120
|
|
BNP-12L
|
0.74-0.80
|
420-455 (5.3-5.7)
|
520-600 (6.5-7.5)
|
84-92 (10.5-11.5)
|
5.8-6.1
|
1.26
|
-0.08
|
110
|
