Performance comparison of motor permanent magnet material ferrite and NdFeB
At present, the commonly used permanent magnet materials include ferrite, NdFeB, Samarium Cobalt, AlNiCo, and rubber magnets. These are relatively easy-to-buy products, with popular performance (not necessarily ISO standards) to choose from.
Each of the above magnets has its own characteristics and application fields. The following is a brief introduction:
Ferrite
Ferrite is a non-metallic magnetic material, also known as magnetic ceramic. We disassemble the traditional radio, and the speaker magnet inside is ferrite. The magnetic performance of ferrite is not high, and the current magnetic energy product (one of the parameters to measure the performance of a magnet) can only be slightly higher than 4MGOe. The biggest advantage of this material is its low price. At present, it is still widely used in many fields. Ferrites are ceramics. Therefore, the processing properties are also similar to those of ceramics. Ferrite magnets are formed by mold and sintered. If machining is required, only simple grinding is required. Due to the difficulty of machining, most ferrite products have simple shapes and large dimensional tolerances. The cube-shaped product is fine and can be ground. Circular, generally only two planes are ground. Other dimensional tolerances are given as a percentage of the nominal size. Due to the wide application of ferrite and its low price, many manufacturers have ready-made rings, squares and other products of conventional shapes and sizes to choose from. Since ferrite is a ceramic material, there is basically no corrosion problem. The finished product does not need surface treatment or painting such as electroplating.
rubber magnet
Rubber magnet is a kind of ferrite magnetic material series. It is made of bonded ferrite magnetic powder and synthetic rubber, and is made by extrusion molding, calendering molding, injection molding and other processes. It has softness, elasticity and twistability. of the magnet. It can be processed into strips, rolls, sheets, blocks, rings and various complex shapes. Its magnetic energy product is 0.60 to 1.50 MGOe rubber magnets Application fields: refrigerators, message sign stands, fasteners for fixing objects to metal bodies for advertising, etc., used in toys, teaching instruments, switches and sensors magnetic sheet. Mainly used in micro motors, refrigerators, disinfection cabinets, kitchen cabinets, toys, stationery, advertising and other industries.
Samarium Cobalt
Samarium cobalt magnet, the main components are samarium and cobalt. Since the two materials themselves are expensive, samarium cobalt magnets are also the most expensive among several magnets. The magnetic energy product of samarium cobalt magnets can currently be 30MGOe, or even higher. In addition, samarium cobalt magnets have high coercivity and high temperature resistance, and can be used at high temperatures of 350 degrees Celsius, so they cannot be replaced in many applications. Samarium cobalt magnets are powder metallurgy products. Generally, according to the size and shape of the finished product, the manufacturer sinters it into a square blank, and then uses a diamond blade to cut it into the finished product size. Since samarium cobalt is electrically conductive, it can be wire-cut. In theory, samarium cobalt can be cut into shapes that can be cut by wire cutting, if the magnetization and larger size issues are not considered. Samarium cobalt magnets have good corrosion resistance and generally do not need anti-corrosion plating or painting. In addition, samarium cobalt magnets are very brittle, so it is difficult to process small-sized or thin-walled products.
NdFeB
NdFeB magnets are widely used and rapidly developing magnet products. It has only been more than 20 years since NdFeB has been widely used since its invention. Due to its high magnetic properties and ease of processing, the price is not very high, so the application field is expanding rapidly. At present, the magnetic energy product of commercial NdFeB can reach 50MGOe, which is 10 times that of ferrite. NdFeB is also a powder metallurgy product, and the processing method is similar to that of samarium cobalt. At present, the maximum working temperature of NdFeB is around 180 degrees Celsius. If it is a harsh environment application, it is generally recommended not to exceed 140 degrees Celsius. NdFeB is very easy to corrode. Therefore, most of the finished products need to be electroplated or painted. Commonly used surface treatments include: nickel plating (nickel copper nickel), zinc plating, aluminum plating, electrophoresis, etc. If working in a closed environment, phosphating can also be used. Due to the high magnetic properties of NdFeB, it is used to replace other magnetic materials in many occasions to reduce product volume. If ferrite magnets are used, the size of the current mobile phone will probably not be smaller than half a brick.
AlNiCo
Alnico magnets are available in both casting and sintering processes. There are more castings in China. The magnetic energy product of AlNiCo can reach 9MGOe, and one of the biggest features is high temperature resistance, and the working temperature can reach 550 degrees Celsius. However, AlNiCo is very easy to demagnetize under reverse magnetic field. If you force two AlNiCos with the same pole orientation (two Ns or two Ss) together, the magnetic field of one of the magnets will be pushed back or reversed. Therefore, it is not suitable for working under reverse magnetic fields (such as motors). AlNiCo is very hard, and although grinding and wire cutting can also be performed, the cost is high. The finished products generally supplied are either ground or not. AlNiCo is widely used in the sensor field.
Hunan Broad Permanent Magnet Co.,Ltd
Mr.Bade Wu
Tel: +86 731 89723018 M.P: 13974929339
Email: bade@bromag.com.cn
Add: 1218-1219, Building B, Accord International, No. 61 Lufeng Road, Changsha 410205 ,China
