- Characteristics Distribution Chart
- Standard Magnetic Characteristics
- Manufacturing Process
- Magnetic Characteristics
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| Material Symbol |
Magnetic Property |
Sintered Density |
Shrinkage |
| Br |
bHc |
iHc |
[BH]max |
| kG |
T |
kOe |
kA/m |
kOe |
kA/m |
MGOe |
kJ/㎥ |
g/㎠ |
% |
| SSM-C |
4.10 ~ 4.30 |
0.41 ~ 0.43 |
3.10 ~ 3.30 |
247 ~ 263 |
3.30 ~ 3.60 |
263 ~ 286 |
4.0 ~ 4.4 |
31.8 ~ 35.0 |
4.90 ~ 5.00 |
13.0±1 |
| SSM-H |
3.80 ~ 4.00 |
0.38 ~ 0.40 |
3.60 ~ 3.80 |
286 ~ 302 |
4.60 ~ 5.00 |
366 ~ 398 |
3.4 ~ 3.8 |
27.1 ~ 30.2 |
4.75 ~ 4.85 |
11.5±1 |
| SSM-K |
4.10 ~ 4.30 |
0.41 ~ 0.43 |
3.70 ~ 4.00 |
294 ~ 318 |
4.20 ~ 4.60 |
334 ~ 366 |
3.9 ~ 4.3 |
31.0 ~ 34.2 |
4.90 ~ 5.00 |
13.0±1 |
-
- Magnetic properties are determined by additives and fine milling time
Pressing conditions are as follows ;
- Magnetic field strength : 10,000 Oe ~13,000 Oe
- Green density : 3.2 ~ 3.4 g/㎤
- Pressure : 0.4~0.5 ton/㎠
- Sintering temperature : 1,200~1,260 ℃
- Typical Shapes & Dimensional Tolerances
- Physical and Mechanical Characteristics
- Ferrite Magnets are hard ceramic materials in which solidified particles are densely combined. However, ceramic magnet materials are inherently brittle and can be chipped and broken if dropped on the hard ground and rubbed each other.
It is recommended that they be not used for structural purpose since they are low in tensile and flexural strength.
- Thermal Characteristics
- Temperature Changes and Shifting of Cunic Point
- Predicting magnetic performance, temperature is a critical factor. In case of Union ferrite magnets, temperature coefficient of the residual flux density ΔBr/Br/ΔT indicates the negative property to the degree of around ?0.2%/℃, and the intrinsic coercive force iHc indicates the positive property of around +0.25~0.5%/℃.
- As shown in Fig.1, when the intrinsic coercive force of ferrite magnets is low, the Cunic point (the point in which B-H curve falls sharply) goes to the second quadrant, but this Cunic point changes its position according to temperature changes. For example, when the temperature of ferrite magnets goes down, this Cunic point shifts gradually toward the Br axis from its original position. This is because, as the temperature falls, residual flux density(Br) increases(negative property), but, on the other hand, the intrinsic coercive force (iHc) decreases (positive property).
- Reversible Demagnetization at Low Temperatures
- When designing magnetic circuit of ferrite magnet, the demagnetization by temperature changes is one of the most significant factors to be considered.
- In fig.2, when the operating line of magnet(permeance coefficient : Pc1) at room temperature is sufficiently higher than the Cunic point, the operating point a1 shifts to a2 on B-H curve shown in dotted line at low temperature. In this case, when returned to room temperature, the operating point returns to the original point a1 as the point a2 is at the higher position than the Cunic point. Therefore, the magnet is not affected in demagnetization by temperature.
- Irreversible Demagnetization at Low Temperatures
- In fig.2, when the operating line of magnet(permeance coefficient Pc2) at room temperature is slightly higher than the Cunic point, the operating point b1 shifts to b2 on B-H curve shown in dotted line at low temperature. When returned to room temperature, the point b2 shifts to R2, and the point R2 corresponds to the point b3 on the operating line pc2. But, as the operating line of the magnet remains unchanged, the operating point is the point b3 on the minor loop originating from R2. In this case, the magnetization amount of the magnet by irreversible process is Bd1- Bd3.
- The analysis of demagnetizing effect by external magnetic field
- The analysis of demagnetizing effect by external magnetic field
- Generally, the characteristics of permanent magnets in magnetic circuits are shown by the B-H curve in the second quadrant, and J-H Curve (SI unit / CGS unit : 4πI-H) shows the magnetizing strength of magnet itself.
The analysis of demagnetization effect by external magnetic field is based on the B-H Curve in the second quadrant as well as on the B-H Curve extending into the third quadrant and J-H Curve (4πI-H Curve).
- In fig-3, point Q1 is the operating point on the B-H Curve for the operating line Pc found from the magnetic circuit and the corresponding point on the J-H Curve is point B.
When the demagnetizing field (-H1) is applied to the magnet, the operating point moves from A1 on the J-H Curve to the operating line through A1′ on the B-H Curve, and the operating point shifts to Q2 after the demagnetizing field is removed. We can realize that flux density at operating point after application of the demagnetizing field shifts from Bd0 to Bd1 , on the B axis. Finally, the magnet is affected to the degree of ΔBd (=Bd0 ? Bd1) by external magnetic field.
And, supposing that larger demagneting field is loaded as like (-H2) in Fig.3, the point A2 on the J-H Curve and the point A2’ on the B-H Curve are positioned lower than the Cunic point.
The operating point shifts to Q3 after the demagnetizing field is removed.
Therefore, Demagnetizing effect of the magnet occurs more than the loading of ?H1 . This tells us that the demagnetizing amount depends largely on the strength of external magnetic field.
As shown in the following formula, the demagnetizing ratio by demagnetizing field depends much on not only the strength of demagnetizing field but also magnetic characteristics (the shape of B-H Curve & minor loop) or permeance coefficient.
-
- Demagnetizing ratio (%) at(-H1)= Bd0 - Bd1
- Demagnetizing ratio (%) at(-H2)= Bd0 - Bd2
- Bd1 : the magnetic flux density at the operating point which is slightly affected by application of demagnetizing field.
- Bd2 : the magnetic flux density at the operating point which is greatly affected by application of demagnetizing field.
- To prevent demagnetizing effect of external magnetic field
- Ferrite magnets can be demagnetized by the effect of external magnetic field. Therefore, it is recommended that the material of higher intrinsic coercive force be selected in advance, especially in the field of application of demagnetizing field such as generators and motors in which the operating point is not lowered than the Cunic point on B-H Curve by the effect of demagneting field.
- R&D Equipment
