MAGNETIC CHARACTERISTICS – SINTERED HARD FERRITE MAGNETS
Rev. Temp. -coeff
|Ferric induction||Max. |
|Hard ferrite magnets 1)||kJ/m3 |
|approx. %/K||kA/m |
|approx. °C||approx. g/cm3|
|HF 8/22 Ba isotropic dry pressed||8,5||8,0||220||215||-0,19 2)||135||220||1000||250 3)||4,80|
|HF 24/16 Ba anisotropic dry pressed||25,5||24,0||365||350||-0,19 2)||155||160||800||250 3)||5,00|
|HF 8/26 Sr isotropic dry pressed||8,5||8,0||220||215||-0,19 2)||135||260||1000||250 3)||4,70|
|HF 24/23 Sr anisotropic dry pressed||25,5||24,0||365||350||-0,19 2)||210||230||1000||250 3)||4,80|
|HF 26/24 Sr anisotropic dry pressed||27,0||26,0||380||370||-0,19 2)||220||240||1000||250 3)||4,80|
|HF 28/26 Sr anisotropic wet pressed||30,0||28,0||395||385||-0,19 2)||240||260||1000||250 3)||4,85|
|HF 28/28 Sr anisotropic wet pressed||30,0||28,0||395||385||-0,19 2)||260||280||1000||250 3)||4,85|
|HF 30/26 Sr anisotropic wet pressed||31,5||30,0||405||395||-0,19 2)||240||260||1000||230 3)||4,85|
1) All values were determined with standard samples according to IEC 60404-5. With unusual geometries, especially with thin walls or narrow pole pitches, deviations from the mater
2) In the temperature range from 20 °C to 100 °C.
3) The max. operating temperature depends on the magnet dimension and the specific application. Please contact our application engineering for more information.
4) For binder PA 6 the magnetic values for HcB min./HcB typ. are reduced by -10 kA/m each and HcJ min./HcJ typ. by -30 kA/m each.
5) For magnets with PPS as binder, the chemical resistance to oils, grease, motor oils etc. is significantly better than for PA-bonded magnets; however this has to be checked in individual cases.
6) On request.
w: axially pressed in the die
h: highly residual materials - isostatically pressed and separated or diametrically pressed in the die
pw: plastic bonded, pressed
p: plastic bonded, injection-moulded
q: diametrical, pressed in tool
Chemical element of the second group (alkaline earths). The most important mineral is the heavy spar. During magnet production it is added to the iron oxide in the form of barium carbonate, and results when presintering in the compound BaO • 6Fe2O3 (barium ferrite).
Chemical element of the second group (alkaline earths). It is found in the minerals strontianite and coelestine. Strontium is added in form of strontium carbonate instead of barium carbonate and results in hardferrite magnets with specially high coercive field strength.
Description that a property is independent of the direction. For a magnet, this means that all molecular magnets (the smallest magnetic particles) have different distributions. This apparent chaos balances the positions of all the molecular magnets, thus also balancing their effect toward the exterior. If a magnet prepared under isotropic conditions is magnetized, only the molecular magnets already oriented in the direction of magnetization will be magnetized. This is why magnets of the same material prepared under isotropic conditions are weaker than magnets prepared under anisotropic conditions.
The opposite of isotropic describes that a property depends on the direction. For a magnet, this means that all molecular magnets have the same orientation. This can be achieved by preferential orientation of the base material. The magnetic values of the magnets prepared under anisotropic conditions are clearly higher than those of the magnets prepared under isotropic conditions.
Description of production procedure of dry molded magnets. Dry molded magnets are manufactured from magnetic powder. This technique is mostly used for small magnets.
Description of production procedure of wet molded magnets. Wet molded magnets are manufactured from wet magnetic mud. The magnetic values of the wet molded magnets are better than those of dry molded magnets. However, there are only few possibilities of forming the wet molded magnets and the molding cycles are much longer.
The final values Br (remanence), Hc (coercive field strength) and (B*H)max. (energy product) are the most important magnetic properties of a permanent magnet. The greatest possible energy product (B*H)max. describes the highest energy density that can be achieved with a material. In general, the following applies: The higher the energy density, the smaller the magnetic volume (V) required for a certain task under otherwise identical conditions.
Remanence is understood as meaning the remaining magnetism in a particle, after removing the magnetizing field. The term remanence is the associated remaining flux density. The remaining magnetism is formed by a previously used magnetic field, such as that of an electrified coil giving the particle its own magnetic field by virtue of induction.
Stands for the reversible temperature coefficient and represents the relative change in a physical property as a function of a change in temperature by one Kelvin.
Stands for the magnetic field strength required to completely demagnetize ferromagnets. A high coercive field strength means that a magnet exhibits high stability against demagnetization. Please note that the coercive field strength is highly temperature-dependent.
Denotes the maximum temperature at which the magnet can still be used. It is far below the Curie temperature. Please note that the maximum operating temperature is a function of the magnet geometry and the opposite fields occurring in use. This means that the values stated in the data sheets are only guide values.
The density of a body is the relationship between the mass and the volume and describes whether a body is relatively light or heavy.
Harry H. Binder: Lexikon der chemischen Elemente, S. Hirzel Verlag, Stuttgart 1999.