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Cast/Sintered - Bonded
 

Cast/Sintered Magnets

 
Alnico Magnets
Very sensitive to counter field but highly resistant against corrosion, for high temperature application with low temperature coefficient.
General Information: Alnico magnets are produced by casting process or by pressing and sintering process. The magnets are sensitive to counter field and highly resisitant against corrosion. They can keep their magnetism up to 550°C and have a very low temperatur coefficient.
The material is composed of iron, cobalt, nickel, aluminium, copper, and niobium. Sintered alnico magnets can be made in more complex shapes than cast alnico which must be machined mainly by grinding.
Temperature Effects: Alnico magnets tend to be very stable with respect to temperature. Changes in magnetization are reversible and loss of magnetization can be recovered by remagnetization for temperatures up to 538°C.
Applications: Alnico magnets are mainly used for speakers, microphones, motors, measuring instruments, flywheel generators, sensors, holders, stepping motors, coupling systems, sensors for motion control, etc.
Data Sheets: Cast Alnico
Sintered Alnico
   
Ferrite Magnets
The material is composed of Iron Oxide, Strontium or Barium, and other materials added. Ferrite magnets are very popular and widely used because of their excellent resistance to demagnetizaion, corrosion, and their low cost.
General Information:
Ferrite magnets are manufactured by pressing or sintering. These magnets can be both anisotropic and isotropic. Anisotropic grades are oriented in the manufacturing direction and must be magnetized in the direction of orientation. Isotropic grades are not oriented and can be magnetized in any direction.
The basic shape is given by the mold, like segment, disc, ring, rod, bar and block. After pressing the magnet will be sintered, then cut, ground and/or drilled, finally magnetized if desired. The material can withstand corrosion to a great extent. Ferrite magnets have an excellent price/quality ratio.
This class of magnet is very hard, brittle and performs lower energy characteristics compared to other magnetic materials.
Temperature Effects: The magnetic properties remain nearly constant in the temperature range of -40°C to +250°C. Versus high temperature the magnetic force will decrease.
Applications: Hard ferrite (ceramic) magnets have a wide application range. The most common used applications are:
electrical motor, loudspeaker, sensor, holder, separation, etc.
Data Sheets: Hard Ferrite
   
Samarium Cobalt Magnets (SmCo)
This group is formed by the magnets Samarium Cobalt (SmCo5 and Sm2Co17). Their main elements, the so-called Rare Earth Sm and Nd, belong to the lanthanide metal series of the periodic system of elements.
General Information: SmCo magnets are manufactured by sintering process. They are anisotropic and can only be magnetized in the direction of orientation. In general, magnetizing fields of approximately 30 to 45KOe are required to saturate SmCo magnets.
These magnets possess very high magnetic properties, excellent thermal stability, while remaining resistant to corrosion. These characteristics make SmCo magnets ideal for applications requiring a resistance to wide-ranging temperatures and rough environments. They provide high stability, but cause higher prices as well.
Temperature Effects: SmCo magnets have an operating temperature of up to 300-350°C, depending on the grade and permeance coefficient.
Applications: Charged particle beam guidance, headphones, holding systems, instruments, loudspeakers, magnetic bearings, magnetic couplings, magnetic resonance, magnetic separations, microphones, particle accelerators, relays, switches, as well as many other applications.
Data Sheets: Sintered Samarium Cobalt
   
Neodymium Iron Boron Magnets (NdFeB)
Best in magnetic performance and energy. The NdFeB magnet is currently the strongest one available.
General Information: Neodymium Iron Boron (NdFeB) magnets, of the Rare Earth class, have been commercially available since the mid -1980's. Their popularity has grown rapidly due to their high Maximum Energy Product and their wide range of available shapes, sizes, and grades.
Today, a Remanence of over 1,4 Tesla is possible. Energy products of up to 50MGOe are currently available. The majority of NdFeB magnets are anisotropic and can only be magnetized in the orientation direction. In general, magnetizing fields of approximately 30KOe are required to saturate NdFeB magnets.
An important disadvantage of the NdFeB magnet is its sensitivity to corrosion. Therefore, to prevent undesired oxidation, the finnished magnets are coated with a zinc-, nickel-, tin-, al-, au- or epoxy layer. The NdFeB magnets are produced in big blocks which are pressed in a mold and then sintered. A smaller block, a disc, a ring, a bar or a rotor will be cut out of the big block by computer controlled electrowire or by diamond blade, drilled with special drills, and finally ground.
The longer the more, NdFeB magnets will replace, where ever possible, the SmCo magnet, due to its lower price.
Temperature Effects: The magnetic properties of NdFeB deteriorate significantly when exposed to temperatures exceeding 130°C, depending on the grade of material and the permeance coefficient. As a rule, NdFeB magnets with a higher permeance coefficient can sustain higher temperatures without loss of magnetic properties. Operational temperatures or up to 200°C are possible.
Applications: Motors, generators, charged particle beam guidance, headphones, holding systems, instrumentation, loudspeakers, magnetic bearings, magnetic couplings, magnetic resonance, magnetic separations, microphones, particle accelerators, relays, switches, as well as many other applications.
Data Sheets: Sintered Neodymium Iron Boron (see also: weight loss graph)
 
 
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