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Stabilizing elements and methods of permanent magnet materials

Date:2022-06-29   Author:XINDA MOTOR
Magnets can attract metals such as iron and nickel diamonds. Commonly known as magnets, they can be divided into permanent magnets that are generally appreciated, and electromagnets that have magnetic properties when energized.

There are many types of magnets, generally divided into two categories: permanent magnets and soft magnets. The magnets we call generally refer to permanent magnets.

Permanent magnets are divided into two categories:

The first category is: metal alloy magnets including NdFeB magnets (Nd2Fe14B), samarium diamond magnets (SmCo), AlNiCo magnets (ALNiCO) The second category is: ferrite permanent magnet materials (Ferrite)

1. NdFeB magnet: It is the magnet with the highest commercial performance found at present. It is called the magnetic king. It has extremely high magnetic performance and its maximum magnetic energy product (BHmax) is more than 10 times higher than that of ferrite. The machinability of its wooden body is also quite good. Operating temperature up to 200 degrees Celsius. Moreover, its texture is hard, its performance is stable, and it has a good price/performance ratio, so it is widely used. However, because of its strong chemical activity, it must be treated with a surface coating. (such as Zn.N. electrophoresis, passivation, etc.).

2. Ferrite magnet: its main raw materials include BaFe12019 and SrFe12019. It is manufactured by ceramic process method, the texture is relatively hard, and it is a brittle material. Because ferrite magnet has good temperature resistance, low price and moderate performance, Has become the most widely used permanent magnet

3. AlNiCo magnet: It is an alloy composed of aluminum, nickel, cobalt, iron and other trace metal elements. The casting process can be processed into different sizes and shapes, and the machinability is very good. Cast aluminum-nickel drill hydromagnetic has the lowest reversible temperature coefficient, and the working temperature can be as high as 600 degrees Celsius. Aluminum-nickel drill permanent touch products are widely used in various instrumentation and other application fields.

4. Samarium diamond (SmCo) is divided into SmCo5 and Sm2Co17 according to the different components. Due to its high material price, its development is limited. As a rare earth permanent magnet, samarium cobalt (SmCo) not only has a higher magnetic energy product (14-28MGOe), the coercive force of Kefei and good temperature characteristics. Compared with NdFeB magnets, samarium cobalt contact iron is more suitable for working in high temperature environment.

The ability of a permanent magnet to support an external magnetic field is due to crystal anisotropy within the magnetic material that "locks" small magnetic domains in place. Once the initial magnetization is established, these positions remain the same until a force exceeding the locked magnetic domain is applied, and the energy required to interfere with the magnetic field produced by the permanent magnet varies for each material. Permanent magnets can generate extremely high coercivity (Hcj), maintaining domain alignment in the presence of high external magnetic fields. Stability can be described as the repetitive magnetic properties of a material under specified conditions over the life of the magnet. Factors that affect magnet stability include time, temperature, changes in reluctance, adverse magnetic fields, radiation, shock, stress, and vibration.

Time has little effect on modern permanent magnets, which studies have shown change immediately after magnetization. These changes, known as "magnetic creep," occur when less stable magnetic domains are affected by thermal or magnetic energy fluctuations, even in thermally stable environments. This variation decreases as the number of unstable regions decreases. Rare earth magnets are unlikely to experience this effect because of their extremely high coercivity. A comparative study of longer time versus magnetic flux shows that newly magnetized permanent magnets lose a small amount of magnetic flux over time. For more than 100,000 hours, the loss of samarium cobalt material is basically zero, while the loss of low permeability Alnico material is less than 3%.