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
  • Wide range of applications
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Ferrite magnets

Detailed product description

Ferrite magnets or ceramic magnets are the most used magnets with a maximum energy product from 1 to approx. 4.3 MGOe. Ferrite is the cheapest magnet material and has a high corrosion resistance, which means a coating is not necessary. Ferrite magnets can be produced both isotropic and anisotropic and the usage temperature is a maximum of 225˚C.

The applications are very broad; think about products such as megaphones, microwaves, measuring equipment, toys, motors, reed-contacts etc.

FERRITE OVERVIEW

Developed in the 1950’s, ferrite is of a similar strength to alnico.
Ferrites are chemical compounds that consist of ceramic materials with iron (III) oxide (Fe2O3) as the key element.
Here at Goudsmit we specialise in the supply of hard ferrites. This is a type of permanent magnet.
Hard ferrite magnets are made by pre-sintering the required chemical components and then fine milling the resulting ceramic. This powder is then wet or dry pressed and again sintered before being ground to size.
Ferrite stands out in the magnet industry for three key reasons:
1. It’s the least expensive of the commercial magnetic materials (Samarium Cobalt, Alnico, and Neo)
2. It has the lowest physical properties of all the magnetic materials
3. It has high energy product to cost ratios
 

FERRITE APPLICATIONS

As the material is ceramic, it will not rust and it can be used uncoated in almost all applications. Ferrite is a popular choice for a variety of products including:
• Loudspeakers
• Microwave ovens
• Magnetic filters
• Drives for pumps
• Motors and Generators
 

KEY BENEFITS OF FERRITE

Ferrite is largely popular within the magnetic industry due to the many benefits it brings about:
• Inexpensive yet strong; ferrite demonstrates a good balance between strength and affordability
• It can be magnetised with multiple poles if necessary
• It does not demagnetise easily
• Ferrite does not corrode


KEY CHALLENGES

Although there are many advantages, there are a few downsides to consider when you’re designing a product with ferrite. Things to be aware of are:
• Its properties degrade linearly as temperature increases
• Generally, ferrite tends to be hard and brittle, meaning it breaks easily
• Ferrite is much weaker than rare earth magnets – typically offering around 1/7th the pull force of a similarly sized
   NdFeB magnet


TECHNICAL DETAILS FERRITE MAGNETS

Here are a few key facts:
• Its density is 0.180 lbs. per cubic inch
• The magnetising field required for saturation is about 10kOe
• Solid sintered ferrite magnets can be wet or dry pressed
• Available grades range from 0103 to 0404, where the first 2 digits represent BHmax; and the second two digits
  represent intrinsic coercivity (Hci)


MANUFACTURING METHODS AND PROCESSES 

There are various manufacturing methods and processes available for ferrite magnets (like those discussed previously for Neo and Samarium Cobalt):
• Sintering is the most common process carried out. It involves forming a solid mass of magnetic material through
   compacting with pressure and heat.  
• Injection Moulding can form bonded magnetic material into complex shapes, and can be moulded directly onto
   other parts to form magnetic assemblies.
• Calendaring allows the bonded magnet material to be made into flexible magnetic sheets and rolls.
• Extruding is the process used to create objects of a fixed cross-sectional profile. A material is pushed through a
   die of the desired cross-section.


MACHINING FERRITE MAGNETS

• Ferrite is brittle, and prone to chipping and cracking. Therefore, special machining techniques must be used to
  machine ferrite material.
• Here at Goudsmit we are fully equipped to machine these materials to your design specifications.


SURFACE TREATMENTS for Ferrite

An important advantage when choosing Ferrite is that no surface treatments are necessary. This is because ferrite is inert and it does not oxidise. However, ferrite magnets can be coated with various epoxy coatings for hygiene purposes if required for your application.


PRECAUTIONS when working with Ferrite

• Since being hard and brittle, ferrite will shatter if dropped and so special care must be taken when handling 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