Characteristics of ferrite materials

Ferrite material, also known as oxide magnetic material, is a composite oxide composed of iron and other metals. Its magnetism belongs to ferromagnetism. It is a super exchange interaction between magnetic metal ions separated by oxygen ions, so that the magnetic moments of magnetic metal ions at different lattice positions are arranged in reverse. If the magnetic moments of the two are not equal, they show strong magnetism. Soft ferrite is one of the most productive and widely used ferrite materials. The main characteristics of these materials are high initial permeability and low coercivity. The main lattice structure is spinel structure. According to the classification of chemical composition, soft ferrite materials mainly include MnZn system, NiZn system and MgZn system; If classified according to the application characteristic parameters, it can be divided into high permeability, power ferrite materials, high frequency ferrite materials, high resistivity materials, very high frequency soft ferrite materials (hexagonal high frequency ferrite), high frequency high power ferrite materials, etc

MnZn ferrite has high initial permeability, high saturation magnetic induction strength and low loss in the radio intermediate frequency or low frequency range. It is the ferrite material with the best magnetic properties in the frequency band below 1 MHz. Initial permeability of commonly used MnZn ferrite μ I = 400-20000, saturated magnetic induction BS = 400-530mt.

The service frequency of NiZn ferrite is 100kHz ~ 100MHz, up to 300MHz. This kind of material has low permeability and high resistivity, generally 105 ~ 107 Ω cm. Therefore, the high-frequency eddy current loss is small, and it is the best material with magnetic properties in the high-frequency band above 1MHz. Permeability of commonly used NiZn materials μ I = 5-1500, saturated magnetic induction BS = 250-400mt.

MgZn ferrite material has high resistivity and is mainly used to make deflection coil magnetic core of picture tube or display tube.

Characteristics of magnetic particle core material

The magnetic particle core is a magnetic core made of ferromagnetic particles with small particle diameter (0.5 ~ 5 mm) and insulating medium. It is generally annular or E-shaped. The electromagnetic characteristics of magnetic particle core depend on the permeability of metal powder material, size and shape of powder, filling coefficient, content of insulating medium, forming pressure, heat treatment process, etc. The magnetic particle core is mainly used for the inductor core. Because the metal soft magnetic powder is surrounded by insulating materials to form a dispersed air gap, the high-frequency eddy current loss of the metal soft magnetic material is greatly reduced, so that the magnetic particle core has anti saturation characteristics and broadband response characteristics. It is especially suitable for making resonant inductors, power factor correction inductors, output filter inductors, EMI filter inductors, etc.

Common magnetic particle cores mainly include iron powder core, iron silicon aluminum powder core, high flux powder core and permalloy powder core (MPP).

Iron powder core is composed of carbon based iron magnetic powder and resin carbon based iron magnetic powder. Due to its low price, iron powder core is still the largest magnetic powder core with permeability of 10 ~ 100.

The typical composition of Fe Si Al powder core is 9% Al, 55si and 85. Due to the addition of silicon and aluminum to pure iron, the hysteresis expansion coefficient of the material is close to zero, which reduces the ability of the material to convert electromagnetic energy into mechanical energy. At the same time, it also reduces the material loss, so that the loss of iron silicon aluminum powder core is lower than that of iron powder core. The saturation magnetic induction intensity of iron silicon aluminum powder core is about 1.05t, and the magnetic permeability has 5 kinds, such as 26, 60, 75, 90 and 125, which has stronger resistance to DC bias than iron powder core. Due to the absence of organic components, the iron silicon aluminum powder core has no aging problem, and the working temperature can reach 200 ℃.

The composition of high flux powder core is: 50% Ni, 50, The saturation magnetic induction intensity is about 1.4T, and the permeability is 14, 26, 60, 125, 147, 160. It is the material with the strongest DC bias resistance in the magnetic particle core (for example, the HF material with permeability of 60 is still not saturated under 1000oe magnetic field). The loss of the magnetic core is similar to that of iron powder core, which is much larger than that of iron silicon aluminum. It is mainly used in high DC bias, high DC and low frequency AC circuits, as well as line filters, AC inductors, output inductors, power factor correction inductors, etc. the price is higher than that of iron powder core and iron silicon aluminum powder core.

The composition of molybdenum permalloy powder core (MPP) is 81% Ni, 2% Mo, 19, The saturation magnetic induction intensity is low, about 0.75T, the permeability varies widely, from 14 to 550, the hysteresis expansion coefficient is close to zero, and the temperature stability is excellent (for materials with permeability less than 330, the relative change of permeability is less than 0.4% from - 60 ℃ to 80 ℃). It has the lowest magnetic core loss in the magnetic particle core, and the anti DC bias ability is second only to that of iron silicon aluminum powder core. Due to the high nickel content, The price is also the most expensive among the magnetic particle cores.

Characteristics of silicon steel and Fe Ni alloy

Silicon steel (ferrosilicon alloy) has the characteristics of good stability, good environmental adaptability and high magnetic flux density. It is a soft magnetic material with the widest use and largest consumption in power and electronic industry. Silicon steel is a polycrystalline metal alloy of cubic system. The performance of silicon steel sheet is affected by seven factors: silicon content, impurities (C, O, s, Mn, P, etc.), grain orientation, stress, grain size, steel sheet thickness and steel sheet surface quality. There are three main measures to improve the performance of silicon steel sheet: changing grain structure, adjusting silicon content and reducing strip thickness. Silicon steel sheet, also known as electrical steel sheet, can be divided into hot-rolled electrical steel (containing silicon 2% - 4.5%), cold-rolled non oriented silicon steel (containing silicon 0.5% - 3%) and cold-rolled oriented silicon steel (containing silicon about 3%). In the late 1980s, non oriented strips with silicon content of 6.5% (hysteresis tends to zero under this composition) can be mass produced, which can further reduce the noise.

Iron nickel alloy, also known as permalloy, with nickel content in the range of 30% - 90%, is mainly in the shape of strip. It is mainly characterized by high permeability and minimal coercivity under weak and medium magnetic field, good processability and good rust prevention performance; After specific processing, good magnetic properties can be obtained, such as initial permeability of more than 100000, maximum permeability of more than one million, coercivity of less than 2 MOE, rectangular ratio coefficient close to 1, maintaining constant permeability in a wide magnetic field range, etc. Because it contains valuable elements such as tweezers and cobalt, the price of this kind of alloy is high. The thinner the strip, the more expensive it is.

Characteristics of amorphous and ultramicrocrystalline alloys

Amorphous alloy is a new type of soft magnetic material. In crystalline materials, atoms are arranged periodically and orderly in space to form the so-called crystal lattice structure. In amorphous materials, atoms are arranged disorderly in space and there is no macroscopic magnetic anisotropy. Amorphous materials have excellent magnetism and toughness, high resistivity and electromechanical coupling coefficient, and good material properties of corrosion resistance, wear resistance, high strength and high hardness.

Amorphous alloy is an alloy made of iron, nickel and cobalt. The iron content of Fe based amorphous alloy is about 80%, which has high saturation magnetic induction intensity, low iron loss and low price. (end)