Ceramic Magnets (Hard Ferrite Magnets)
Ceramic (Ferrite) Magnets Overview
Ferrite magnets have the advantages of simple production technology and low cost. So they are produced in bulk quantity. Meanwhile they are widely used in many fileds such as used as iron cores in electrical inductance wires. The main rare material of ferrite manget are Iron oxide , Barium carbonate and Cesium Carbonate.Through the technique of ceramic-producing procedure, their texture are hard belong to fragile materials. This process provides an economical means of production of various shapes and sizes. Because of their anticorrosion ,cheap price and moderate property they have become the most widely-used magnets. They are widely used in automobile motors,screen wipers,engine,warm braws,fuel pump,seat motors,massage armchair,etc. Generally speaking, Ferrite magnets have become an essential material of electronical field.
Ceramic Magnets Properties
| Grade | Br (KGs) |
Hc (KOe) |
Hci(KOe) | (BH)max (MGOe) |
Curie Temp. (°C) |
Max. Op. Temp (°C) |
Inquiry |
|---|---|---|---|---|---|---|---|
| Ceramic 1 | 2.2 | 1.86 | 3.25 | 1.10 | 450 | 300 | |
| Ceramic 5 | 3.8 | 2.4 | 2.5 | 1.1 | 450 | 300 | |
| Ceramic 7 | 3.4 | 3.25 | 4.0 | 2.75 | 450 | 300 | Inquiry |
| Ceramic 8 | 3.85 | 2.95 | 3.20 | 3.5 | 450 | 300 | |
| Ceramic 10 | 4.2 | 2.95 | 3.05 | 4.2 | 450 | 300 |
Machining
Ferrite magnets are formed by compaction in dedicated, multi-cavity dies followed by sintering in high temperature furnaces. This produces a hard, brittle part that requires diamond wheels for grinding to close tolerances. While physically quite strong, these magnets should not be considered a structural member in an assembly. And like most ceramics, they are brittle and should be handled so as to avoid chipping and cracking.
Key Advantages
- Does not rust
- Cheap but strong
- It is hard to demagnetize
- Magnetized with multiple poles is acceptable
- Not necessary for surface treatment
Magnetizing and Handling
Ceramic magnets is farely hard and rather fragile compared with other magnets.They can be magnetized through thickness, diameter magnetized,multi-poles in isotropic magnets and so on. The magnetic power of ceramic magnets is much weaker than that of Sintered NdFeB Magnets. It is very important to keep the magnets from being damaged.
Surface Treatment
Ferrite magnets should not be coated because they are hard to be rusty. Therefore it is unnessary for Ferrite Magnets to be coated
Temperature Effects
Temperature variation can result in both reversible and irreversible changes in magnetization. A reversible change occurs at the rate of approximately -0.2% per degree centigrade. That is, as temperature rises above ambient, induction (Br) will decrease. Coercivity, a measure of resistance to demagnetization, changes at a rate of about 0.27% per degree centigrade. As temperature rises, coercivity of the ferrite magnet will increase! Irreversible changes can result from exposure to very low temperatures, and the magnetic quality is restored only by re-magnetization. Irreversible changes can be avoided by providing an adequate permanence coefficient.