FERRITE MAGNETS

ferrite-magnets

Ferrite Magnets are Composed of Strontium carbonate and iron oxide.
They are charcoal gray in color and usually appear in the forms of discs,
rings, blocks, cylinders, and sometimes arcs for motors.

Manufacturing Ferrite Magnets

A powdered mixture of strontium carbonate and iron oxide is injected
into either a wet press or dry press for forming. During this pressing
process, a magnetic field is applied in the direction of preferred
magnetization to orient the material and increase the magnet’s performance
potential. This magnet is considered “oriented”. If not
exposed to a magnetic field at time of formation, it is called “non-oriented”
(Isotropic).

After the molding process, the material is then sintered at about
1010OC. This process is similar to that of kilting ferrite pottery,
thus the popular name “Ferrite” magnet.

Lastly, the magnet is finish-ground to size with a diamond-bladed
grinding wheel, magnetized, and inspected for shipment.

Attributes of Ferrite Magnets

» High intrinsic coercive force

» Tooling is expensive

» Least expensive material compared to alnico and rare earth
magnets

»Lower service temperature than Alnico, greater than rare earth

» Finishing requires diamond cutting or grinding wheel

» Lower energy product than alnico and rare earth magnets

» Limited to simple shapes due to manufacturing process

» Most common grades of ferrite are 1,5 and 8 (1-8 possible)

» Grade 8 is the strongest ferrite material available

Application of Ferrite Magnets

  • Speaker magnets
  • DC brush less motors
  • Magnetic Resonance Imaging (MRI)
  • Used in magnetic assemblies designed for lifting, holding, retrieving
    and Separating
  • DC permanent magnet motors (used in cars)
  • Separators (Separate ferrous material from non-ferrous)
  • Magnetos used on lawnmowers,and outboard motors

Tolerances

Pressed dimensions are either +/- 2% or +/- 0.5mm whichever is greater.
Cut dimension are either +/- 3% or +/-0.5mm, whichever is greater. Thickness
tolerances are normally ground to +/- 0.1mm.

Visual imperfections such as cracks, porosity, voids, surface finish,
etc., (commonly found in sintered ceramic magnets) do not constitute
cause for rejection.

Machining

Since ferrite material is so brittle, it requires special machining
techniques and equipments. We are fully equipped to cut and grind ceramic
material to your specifications.

Magnetizing and Handling

Ferrite magnet material is extremely brittle and can chip or break
if dropped on a hard surface, or if allowed to “Jump at”
an attracting object. Handle with care.

The weakest grade of Ceramic material is grade 1, which is typically
non-oriented. Grades 5 and 8 are oriented ceramic material. Grade 8
is the strongest ceramic magnet material available (Refer to properties
chart below).

When making magnetic assemblies with ferrite it is typically easier
for production purposes to magnetize the product after assembly.