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Radial Sintered NdFeB Ring Magnet

1. Introduction of Radial Sintered NdFeB Ring Magnet for Motor

Radial Sintered NdFeB Ring Magnet is developed to meet different requirements of permanent magnet servo motor, using the new shaping method by multipole polymerization radial orientation.

The products can be widely used in:

(1) Spindle motor for HDDs(Hard Disc Drive), FDDs (Floppy Disc. Drive); all kinds of permanent magnet Servomotors for robots, machinery; step motor.

(2) Tachogenerators

(3) EPS (Electronic Power Steering System in automobiles), etc.

(4) Actuators.

Compared with segments jointed ring, radial ring magnet can improve the output characteristics and significantly reduce the loss of motor, it has excellent temperature stability, corrosion resistance and temporal stability ,and so on, especially applying for high precision micro & special motor drive.

Outer Diameter(OD) Inner Diameter(ID) Thickness Height Coating BH(max)
Max 150mm Min 10mm Min 2mm Max 50mm Ni / Zn / Epoxy 35·50 MGOe


Item Ring jointed by the segments Radial ring( A complete ring)
Construction Several segment magnets joint into a ring, then add a protecting cover. The radial ring assemblize on the bearing directly, no need to add the protecting cover, simple and quick.
Appearance Precision Assembling by the protecting cover, bearing and several segment magnets, hawing the lower precision. Radial ring directly determines the shape tolerance, the tolerance of outer and inner diameter can achieve +/-0.3mm, and has the good coaxiality and verticality.
Reliability In some cases, the segments will break away from the bearing. Simple mechanism and good reliability

2. Physical Properties

Density ρ 7.6 g/cm3
Vicker Hardness   600 HV
Modulus of Elasticity E 150 Kn/mm2
Compressive Strength   1000 N/mm2
Tensile Strength   78 N/mm2
Flexural Strength   245 N/mm2
Expansion Coeff. ⊥ρ.ρ.d -1 10-6/K
∥ρ.ρ.d 5 10-6/K
Spec.Elec.Resistance ρcl 1.45 10-6Ω·m
Spec.Heat Capacity c 440 J/(kg·K)
Thermal Conductivity λ 8 W/m·K


(1) The cylindrical shape enables higher precision in external dimensions.

(2) As a rotor, can achieve uniform magnetic density flux distribution.

(3) Fastening the magnet is simple, enabling assembly-related cost reductions.

(4) Highly reliability due to enabling rotor construction from a single magnet.

(5) Optional magnetization, including free multiple magnetization, skew-type magnetization possible (Radial anisotropic magnet)

(6) Can obtain sine surface inductive flux distribution (multi-pole oriented magnet)

3. Curve:

4. Magnetic Properties

We have currently the grades as following chart.

Grade Remanence Coercive Force Intrisinc Coercive Force Max. Energy Working Temp.
Br(Gs) Hcb(Oe) Hcj(Oe) (BH)max TW* (℃)
35H 11500-12300 10500 15500 30-35(MGOe) 120
40H 12200-13100 11000 15500 34-40(MGOe) 120
45H 12600-13800 12000 15500 37-45(MGOe) 120
38M 11800-12800 9800 13500 32-38(MGOe) 120
35SH 11500-12300 11500 18500 30-35(MGOe) 150
38SH 11800-12800 11500 18500 32-38(MGOe) 150
42SH 12300-13400 11500 18500 35-42(MGOe) 150
35UH 11500-12300 10500 23500 30-35(MGOe) 180
40UH 12200-13100 11000 23500 34-40(MGOe) 180



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