Soft magnetic material

Soft magnetic material

Soft magnetic materials refer to when the magnetization occurs at Hc not greater than 1000A/m, such materials are called soft magnetic materials. Typical soft magnetic materials can achieve maximum magnetization with the smallest external magnetic field. Soft magnetic material (soft magnetic material) A magnetic material with low coercivity and high permeability.

Soft magnetic materials are easy to magnetize and demagnetize, and are widely used in electrical and electronic equipment. The most commonly used soft magnetic materials are iron-silicon alloy (silicon steel sheet) and various soft ferrites.

Soft ferrite

The characteristics of soft ferrite are: low saturation magnetic flux density, low permeability, low Curie temperature, low medium and high frequency loss, and low cost. The first three lows are its shortcomings, which limit its scope of use. Now (the beginning of the 21st century) is working hard to improve. The latter two lows are its advantages, which are conducive to entering the high-frequency market. Now (the beginning of the 21st century) is working hard to expand.

Taking the loss at 100kHz, 0.2T and 100℃ as an example, TDK's PC40 is 410mW/cm3, PC44 is 300mW/cm3, and PC47 is 250mW/cm3. TOKIN's BH1 is 250mW/cm3, and the loss is constantly decreasing. The domestic JP4E produced by Jinning also reached 300mW/cm3.

Continuously increasing the working frequency is another direction of effort. The operating frequency of TDK's PC50 is 500kHz to 1MHz. FDK's 7H20 and TOKIN's B40 can also work at 1MHz. Philips' 3F4, 3F45, and 3F5 operating frequencies are all over 1MHz. The operating frequencies of domestic Jinning's JP5 and Tiantong's TP5A both reach 500kHz to 1.5MHz. The operating frequency of DMC's DMR1.2K even exceeds 3MHz, reaching 5.64MHz.

Magnetic permeability is the weak item of soft ferrite. Now (the beginning of the 21st century) domestically produced products are generally around 10,000. H5C5 of foreign TDK company and 3E9 of Philips company reached 30,000 and 20,000 respectively.

The research of using SHS method to synthesize MnZn ferrite materials is worth noting. The test results of this method show that the energy consumption and cost of ferrite manufacturing can be greatly reduced. There have been reports of successful trials in China.

Amorphous and nanocrystalline alloys

Iron-based amorphous alloys are competing with silicon steel in the power frequency and intermediate frequency fields. Compared with silicon steel, Fe-based amorphous alloy has the following advantages and disadvantages.

1) The saturation magnetic flux density Bs of the iron-based amorphous alloy is lower than that of the silicon steel, but under the same Bm, the loss of the iron-based amorphous alloy is smaller than that of the 0.23mm thick 3% silicon steel. It is generally believed that the low loss is due to the thin thickness and high resistivity of the iron-based amorphous alloy strip. This is just one aspect, the more important reason is that the iron-based amorphous alloy is amorphous, the atomic arrangement is random, there is no magnetocrystalline anisotropy caused by the atomic alignment, and there is no crystal that causes local deformation and composition shift. Grain boundary. Therefore, the energy barrier that hinders the domain wall movement and the rotation of the magnetic moment is very small and has unprecedented soft magnetism, so the magnetic permeability is high, the coercive force is small, and the loss is low.

2) The iron-based amorphous alloy core has a filling factor of 0.84 to 0.86. Compared with the silicon steel filling factor of 0.90 to 0.95, the iron-based amorphous alloy core of the same weight has a larger volume than the silicon steel core.

3) The working magnetic flux density of the iron-based amorphous alloy core is 1.35T～1.40T, and the silicon steel is 1.6T～1.7T. The weight of the iron-based amorphous alloy power frequency transformer is about 130% of the weight of the silicon steel power frequency transformer. However, even if the weight is heavy, for power frequency transformers of the same capacity, the loss of iron-based amorphous alloy cores is 70% to 80% lower than that of silicon steel.