Ferrite magnets

Short description

Ferrite magnets or ceramic magnets are the most used magnets. The applications of ferrite magnets are very broad.

Characteristics

  • Affordably priced
  • Energy product of 1 to approx. 4.3 MGOe
  • High corrosion-resistance
  • ISO 9001 - ISO/TS 16949 - AS9100c
  • Wide range of applications
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Ferrite magnets

Detailed product description

Ferrite

Ferrite magnets, or ceramic magnets as they are also called, are still widely used. They have a maximum energy product of up to around 4.3 MGOe. Ferrite is the least expensive magnetic material and is highly corrosion-resistant, so no coating is required. Ferrite magnets can be produced to be either isotropic and anisotropic, and the maximum application temperature is 225 °C.

Ferrite was developed in the 1950s and is comparable to AlNiCo magnets in terms of magnetic strength. Ferrite is a chemical compound consisting of a ceramic material with iron oxide (Fe2O3) as the main component, doped with strontium.

Applications

The range of applications is extremely broad. Because the material is ceramic, it does not rust and it can be used without coating in nearly all applications. Ferrite magnets can be found in applications such as:

  • speakers
  • microwave ovens
  • magnetic filters
  • pump drives
  • measuring equipment
  • toys
  • reed switches
  • motors and generators

Advantages

  • inexpensive, yet strong: Ferrite is the least expensive of the commercial magnetic materials; it offers a good balance between strength and affordability;
  • can be magnetized with multiple poles;
  • it does not easily demagnetize;
  • a standard temperature-resistance of up to 225 °C;
  • ferrite is not susceptible to corrosion.

Disadvantages

  • the properties degrade linearly with increasing temperature;
  • ferrite is a hard, brittle material, so it breaks easily;
  • ferrite is much weaker than the rare-earth magnets: it has about one-seventh the tensile strength of a similarly sized neodymium magnet.

Technical details of ferrite

  • density: 5000 kg/m³ ((0.180 lbs./in³);
  • magnetic field required for saturation: ±10 kOe;
  • solid sintered ferrite magnets can be pressed wet or dry;
  • BHmax value of the available range of neodymium grades: 6-36 kJ/m³.

Production methods

  • Sintering: ferrite magnets are produced by pre-sintering the required chemical components and then finely grinding the resultant ceramic. This powder is then wet or dry pressed in a mould and then sintered again.
  • With injection moulding it is possible to form bonded magnetic material having complex contours and to pour it directly onto other components to form magnetic assemblies.
  • The calendering process forms bonded magnetic material into flexible magnetic tapes and rolls.
  • Extruding is used to create objects with a fixed cross-sectional profile by pressing the material through a die having the desired cross-section.

Processing of ferrite magnets

Ferrite is brittle, so it breaks easily. Therefore we use special processing techniques when working with ferrite. Goudsmit Magnetics is fully equipped to process these materials to arrive at your design specifications.

Surface treatment for ferrite

A big advantage of ferrite magnets is that no surface treatment is needed, because ferrite is inert and therefore does not oxidize. It is always possible to coat ferrite magnets with various epoxy coatings, when this is desired, for example, from the hygiene point of view.

Precautions when working with ferrite

Ferrite is a hard and brittle. Pieces break off when the material falls. This must be kept in mind when working with these magnets.

Ferrite Permanent magnets - table

Grade Remanence Normal
coercivity
Intrinsic
coercivity
Maximum
energy product
Max.
operating
Temp.
 

Br
mT

Hcb
kA/m
Hcj
kA/m
BH(max)
kJ/m3
 
  min typ min typ min min typ °C

Isotropic

GSFD-10

210 240 127 159 211 6,4 9,5 225

Anisotropic

GSFD-25 380 400 143 175 147 25 29 225
GSFD-30 390 410 175 207 179 27 31 225
GSFD-33 390 410 239 271 243 27 31 225
GSFD-40 390 410 271 295 307 28 32 225
GSFD-42 415 435 215 239 219 30 33 225
GSFD-44 430 450 247 271 251 33 36 225