Ferrite Magnets - General Information
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| Ferrite Properties |
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Ferrite, also known as Ceramic, magnets were formulated in the 1950s by Phillips in Holland. The major raw material used to manufacture Ferrite magnets is very inexpensive - iron oxide, more commonly known as "rust"! Due to their low cost, they are the most commonly used permanent magnets even today.
A special form of fully dense sintered ferrite magnets is produced using a flexible binder for the ferrite powder. These materials are commonly referred to as "Flexible Magnets".
Key Benefits
- Inexpensive yet strong; a good balance between strength and affordability
- Does not demagnetize easily
- Can be magnetized with multiple poles if necessary.
- Does not rust
Key Challenges
- Hard and brittle.
- Properties degrade linearly with temperature. At 350°F, about 75% of room temperature magnetization is retained, and at 550°F, about 50% is retained.
Quick Facts
- Density - 0.180 lbs per cubic inch
- Saturation magnetizing field required - about 10kOe
- Manufacturing methods - sintering (most common), injection molding, extruding or calendering - the last 3 methods when the material is combined with a carrier. Fully dense sintered Ferrite magnets can be wet or dry pressed - wet pressing leads to higher magnetic properties.
- Shapes available - blocks, bars, discs, rings, arc segments, etc.
- Grades available - from 0103 to 0404. (First 2 digits represent BHmax, and second two digits represent Intrinsic Coercivity, Hci.)
- Sizes - sintered ferrites can be manufactured in blocks up to about 10" x 4" x 1". Extruded Ferrite (otherwise known as Flexible magnets) can be extruded in unlimited lengths. The energy product of Flexible magnets is, however, much lower than that of fully dense, sintered Ferrite magnets.
Surface Treatments
No surface treatments are necessary for Ferrite magnets since they are essentially inert and do not oxidize. However, they can be coated with various epoxy coatings for cleanliness purposes.
CAUTION!
Ferrite materials are very hard and brittle and will shatter if dropped.
