At present, the common permanent magnetic materials are ferrite magnet, NdFeb magnet, SmCo magnet, Alnico magnet, rubber magnet and so on. These are relatively easy to buy, with common performance (not necessarily ISO standards) to choose from. Each of the above magnets has its own characteristics and different application fields, the briefly introduced is as follows.
Neodymium magnet
NdFeb is a magnet which is widely used and developing rapidly.
Neodymium magnet is widely used from the invention to now, but also more than 20 years. Due to its high magnetic properties and easy processing, and the price is not very high, so the application field is expanding rapidly. At present, the commercial NdFeb, its magnetic energy product can reach 50MGOe, and it is 10 times of ferrite.
NdFeb is also a powder metallurgy product and is processed in a similar way to samarium cobalt magnet.
At present, NdFeb’s high operating temperature is around 180 degrees Celsius. For harsh applications, it is generally recommended not to exceed 140 degrees Celsius.
NdFeb is corroded very easily. Therefore, most of the finished products should be electroplated or coated. Conventional surface treatments include nickel plating (nickel-copper nickel), zinc plating, aluminum plating, electrophoresis, etc. If you work in a closed environment, you can also use phosphating.
Due to the high magnetic properties of NdFeb, in many occasions, it is used to replace other magnetic materials to reduce the volume of the products. If you use ferrite magnets, the size of the current mobile phone, I’m afraid not less than half a brick.
The above two magnets have better processing performance. Therefore, the dimensional tolerance of the product is much better than that of ferrite. For general products, the tolerance can be (+/-)0.05mm.
Samarium Cobalt magnet
Samarium cobalt magnets, the main ingredients are samarium and cobalt. Because the price of materials is expensive, samarium cobalt magnets are one of the most expensive types.
The magnetic energy product of samarium cobalt magnets can currently reach 30MGOe or even higher. In addition, samarium cobalt magnets are of highly coercive and high-temperature resistant, and it can be applied to temperatures up to 350 degrees Celsius. So that it is irreplaceable in many applications
Samarium cobalt magnet belongs to powder metallurgy products. General manufacturers according to the size and shape of the finished product needs, burned into a square blank, and then use a diamond blade to cut into the size of the finished product. Because samarium cobalt is electrically conductive, it can be linearly cut. Theoretically, samarium cobalt can be cut into a shape which can be cut linearly, if magnetization and larger size are not considered.
Samarium cobalt magnets have excellent corrosion resistance and generally do not require anti-corrosion plating or coating. In addition, samarium cobalt magnets are brittle, it is difficult to manufacture products in small sizes or thin walls.
Alnico magnet
Alnico magnet has casting and sintering two different processes ways. Domestic produce more casting Alnico. The magnetic energy product of Alnico magnet can up to 9MGOe, and has a big feature is that is of high temperature resistance, working temperature can reach 550 degrees Celsius. However, Alnico magnet is very easy to demagnetize in an inverted magnetic field. If you push two Alnico magnet poles in the same direction (two N’s or two S’s) together, the field of one of the magnets will be retracted or reversed. Therefore, it is not suitable for working in an inverted magnetic field (such as a motor).
Alnico has a high hardness and can be ground and wire cut, but at a higher cost. General supply of finished products, there are two kinds of grinding good or not grinding.
Ferrite magnet / Ceramic magnet
Ferrite is a kind of nonmetallic magnetic material, also known as magnetic ceramics. We take a conventional radio apart, and the horn magnet in it is ferrite.
The magnetic properties of ferrite are not high, the current magnetic energy product (one of the parameters to measure the performance of a magnet) can only do 4MGOe slightly higher. The material has the great advantage of being cheap. At present, it is still widely used in many fields
Ferrite is ceramic. Therefore, the machining performance is similar to that of ceramics. Ferrite magnets are mold forming, sintering out. If it is need to processing, only simple grinding can be carried out.
Due to the difficulty of mechanical processing, so most of the shape of ferrite is simple, and the size tolerance is relatively large. Square shape products are good, can be grinded. Circular, generally grinding only two planes. Other dimensional tolerances are given as a percentage of nominal dimensions.
Because ferrite magnet has been used for decades, many manufacturers have ready-made rings, squares and other products of conventional shapes and sizes to choose.
Because ferrite is ceramic material, there is basically no corrosion problem. Finished products do not require surface treatment or coating such as electroplating.
Post time: Nov-22-2021