Magnetization Process
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- Bu səhifədəki naviqasiya:
- NdFeB Magnet Grade at Various Temperatures NdFeB loses approximately 0.11 % Br for every degree C above 20
- Magnet Materials Materials Typical Shapes Pro Con
- Sintered Alnico AlNiCo
- Samarium Cobalt SmCo
- Neodymium NdFeB
- Manufacturing Processes
- Isostatic pressing
- Compressing in tools
- Casting
NdFeB Magnet Grade at Various Temperatures
NdFeB loses approximately 0.11 % Br for every degree C above 20 °
This is called the Reversible Temperature Coefficient. 15
Magnet Materials Materials Typical Shapes Pro Con Cast Alnico AlNiCo Rods, Bars, U shape and other cast type High Br
High working T Good T coef. Very Low Hc High cost High L/D Requires Cast Sintered Alnico AlNiCo Powder pressed to shape Complex
shapes High Br, T Requires Tool High cost Low market
Blocks, Rings, Arcs, Discs Most flux for $ High usage Low corrosion Low Br Requires tool Simple shapes Samarium Cobalt SmCo Blocks, Rings, Discs Arcs, Segments No corrosion Very low T coef Stable, No tool Very expensive Simple shapes High Co content
Blocks, Rings, Discs Arcs, Segments Highest
magnetic properties No tooling Corrodes Low working T Difficult to Mag Bonded Grades All materials Difficult geometries Can be insert molded or overmolded Complex shapes
Various resins High toolings Low magnetics High volumes There are other magnet materials which are used much less frequently: • Manganese Aluminum Carbon • Iron Chrome Cobalt • Cunife
• Wire drawn Alnico • HDDR type Neo • Extruded Neo • Platinum Iron Neo 16
Highest Properties of Each Magnetic Material Material Br Hc Hci (BH)max ∆
∆
4000 3600 4100 4.0 -.18
Alnico 5 12700 640 650 5.5
-.02 Alnico 9 10500 1500 1520 10.5
-.02 SmCo 5 10000 9500 12500 24.0 -.03
11300 8000 >9000 28.0 -.03
14250 11500 >12000 50.0 -.11
11900 10300 >25000 42.0 -.11
5500 2500 >2500 5.5 -.11
• These materials do not include bonded types • The greatest advances in magnetics are being done in the area of Neo • Neo is becoming stronger and with a higher working temperature • New methods of manufacturing are being developed
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Manufacturing Processes
Depending on the type of material, the following processes are used to manufacture permanent magnets:
pressures in an aligning magnetic field, then sintering it into a solid shape. After sintering, the “ingot” is rough and must be machined to achieve close tolerances. The complexity of shapes that can be pressed using this process is limited. Neodymium and Samarium cobalt powders are compressed to form magnets by:
•
all directions. These magnets have the highest possible magnetic values because of the higher density achieved using this technique.
Compressing in tools: 1. Transverse Field Pressing. The powder is compacted at right angles to the magnetic flux. These magnets have a weaker field compared to the isostatic pressed ones, but stronger compared to the parallel pressed magnets.
2. Parallel Compressing. The powder is compacted parallel to the magnetic field.
NdFeB magnets using melt spun Nd powders that are epoxy coated. The powders are compacted and then heat cured for the epoxy to perform the binding function. These magnets are typically isotropic. Injection Molding Neodymium, Samarium Cobalt, and Ferrite Materials can be manufactured by injection molding. Common binders for injection molding are polyamides. The advantage of using this method is the possibility to get a better tolerance directly from the tool with no required heat treatment, and the magnets can be produced in complex shapes. They can be combined with other materials for over-molding or insert molding.
casting of other metals. Parts are formed in sand casts which can be complex.
rubber binders are made using this method. The process is similar to that for vinyl sheets. Parts are later die cut or stamped from sheets of various thicknesses. 18
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