Есть есть несколько видов мягких магнитных материалов.
Железо и низко углеродистые стали
Железо и низкое углеродистое сталь может быть большинство общее и самое дешевое мягкое магнитное материалы. Они имеют а вполне высоко значение из BS ~2.15 T, который есть только хуже к к дорого Fe-Co сплавы. Но их их удельные сопротивления есть скорее низкие, которые пределы их использование в динамические приложения. Железо и низко углеродистые стали есть обычно используемые для статические%2поток частота приложения, такой как сердечник из электромагнит, реле, и некоторые низкие Мощность Двигатели Для Который Материалы Стоимость Есть Основной Забота.
Железо-кремний сплавы
Addition of a few of silicon to iron will increase its resistivity notably, therefore, is very beneficial for inhibiting the eddy current loss. Despite of slightly decrease of saturation magnetization and Curie temperature, Fe-Si alloys are widely used in electric machines operating at from 50 Hz to several hundreds Hz. To further reduce the eddy current loss, Fe-Si alloys are often rolled to the form of thin strips. The thickness for the most common Fe-Si alloy is equal to or less than 0.35mm. Depending on the conditions of rolling and heat treatment, Fe-Si alloy can be classified as Grain-Oriented (GO) and Non-Oriented (NO). GO Fe-Si is used for transformers, whereas NO Fe-Si is used for electric motors.
Железо-никелевые сплавы
Nickel can be added to iron to form uniform solid solutions in a broad composition range of 35 wt. % to 80 wt. % Ni. The alloys with composition near Fe20Ni80 were named as Permalloy (nowadays people tend to call all the iron-nickel alloy with nickel content higher than 35 wt. % as Permalloy). Minor content of other elements such as Mo, Cu, and Cr are usually added to improve the magnetic properties of Permalloy. Processed by delicate composition adjustment and heat treatment, Permalloy can be one of the softest magnetic material in the world, the permeability of which can be as high as 1 200 000. One of the drawbacks of Permalloys is their saturation magnetization, which is only of about 0.8 T, much lower than that of iron and Fe-Si alloys. With decrease of the nickel content, BS will increase firstly, reach its maxima of 1.6T at around nickel content of 48 wt. %, however, the permeability will not be as good as alloys with high nickel content. Iron-nickel alloy is the most versatile magnetic alloy, its magnetic properties can be tuned by adjusting composition, magnetic annealing, and mechanical rolling, etc. Iron-nickel alloy also presents very good formability, which can be rolled down to as thin as 20 microns. As a result, nickel-iron alloys can be found in wide applications such as magnetic field shielding, ground fault interrupter, magnetic sensors, recording head for magnetic tapes, power electronics, etc.
Железо-кобальт сплавы
Добавление кобальт к железо воля увеличение оба Кюри температура и БС. Д кобальт содержание в в диапазон 33 масс. % к 50 масс. %, БС может быть как высокий как 2.4Т. Хотя не как мягкий как железо-никель сплав, железо-кобальт сплавы настоящий на высокий значение БС среди все все те прочие магнитные сплавы. К увеличение те формуемость, 2 масс. % из ванадий есть добавлено к Fe50Co50 сплав, итак что оно может будет прокатанный вниз к как тонкий как 50 микрон. сложение из ванадий can также увеличение удельное сопротивление из железо-кобальт сплав. Должен к высочайший BS, железо-кобальт сплавы являются необходимые для применения где высокая мощность к вес отношение есть требовательный, такой как двигатели и трансформаторы используемый в космический устройства.
Аморфные и нанокристаллические сплавы
Amorphous alloys, also frequently called metallic glasses, can be produced by rapid solidification. There is no long-range order for the atoms in amorphous alloys, therefore, the resistivity is usually high, and there is no magneto crystalline anisotropy. Furthermore, amorphous ribbons as thin as around 20 to 30 microns can be easily produced by planar flow casting. All these characters guarantee amorphous alloys to be excellent candidates for soft magnets. According to the compositions, most of the commercially available amorphous soft magnets can be classified as Fe-base, Co-base, and (Fe, Ni)-based. For these three types, the total content of Fe, Co, and Ni is about 75-90 wt.%, the remanent are metalloids and glass forming elements such as Si, B, P, C, and Zr, Nb, Mo, etc. Among these types, Fe-based has the highest BS of about 1.6 T and lowest cost. The iron loss of Fe-based amorphous alloy is only one third of that of Fe-Si steel. If the Fe-Si steel in the power transformers can be replaced by Fe-base amorphous alloy, a huge amount of electric power can be saved, but the materials cost for the latter is higher. Co-based amorphous alloys usually have BS lower than 0.8 T but much higher permeability and near zero value of magnetostriction, which is comparable with the softest permalloy, and can perform even better at higher frequencies due to its higher resistivity. (Fe, Ni)-based amorphous alloys present medium magnetic properties compared with the other two.
Amorphous state is a metastable state. Upon heating above a critical temperature, nucleation and growth of microcrystals take place rapidly. For conventional amorphous soft magnetic alloys, during the crystallization, the size of microcrystals will grow up to several hundreds of nanometers in very short time and degenerate the soft magnetic properties severely. Nevertheless, people found that by addition of certain amount of Nb and Cu to Fe-based amorphous alloy, the crystallization process can be under control and a uniform distribution of nanocrystal with size about 10 nm in the amorphous matrix can be obtained. The magnetic properties of such a Fe-based nanocrystalline alloy are even softer than the corresponding amorphous alloy, i.e., higher permeability and lower coercivity, although the BS is also lower (~1.2 T). The source of the excellent soft magnetic properties for Fe-based nanocrystalline alloys is that both the value of magneto-crystalline anisotropy and magnetostriction can be tuned to near zero. Permalloy and Co-based amorphous alloys can also have near zero value of magneto-crystalline anisotropy and magnetostriction, but the BS of Fe-based nanocrystalline alloys is much higher. Therefore, nanocrystalline alloys may be one of the most promising soft magnetic materials. They are widely used in wireless charger, high frequency inductor, magnetic sensor, electromagnetic shielding, ground fault interrupter, and so on.
Мягкие магнитные композитные
As mentioned before, the thickness of soft magnetic materials plays an important role for reducing eddy current losses, thus the soft magnetic alloys should be made in the form of thin lamination for dynamic uses. If we break down the other two dimensions of the soft magnetic strip, i.e., we use the soft magnetic alloys in the form of powders, then the eddy current losses can be further reduced, and the components made by which can be used at much higher frequencies. To realize such a utilization, the alloy powders are first prepared (in most cases by atomization methods), the particles then should be coated with an insulation layer, after that, the powders are mixed with a tiny amount of lubricant and compressed at an intense pressure of 600-800 MPa to the final shape. Soft magnetic products made by such processes are called Soft Magnetic Composites (SMCs) or powder cores. Another merit of SMCs is that they can be made into various specially shaped cores which are hardly made by the traditional lamination stacking methods, which benefits for novel design of electromagnetic devices. The main drawback of SMCs is that their permeabilities are relatively low. Nowadays the most common SMCs are made by powders of Fe, Fe-Si, Fe-Si-Al, Fe-Ni, amorphous and nanocrystalline alloys, etc.
Софт ферриты
Все мягкие магнитные материалы упомянутые вышеупомянутые есть металлы, следовательно, вихрь ток эффект нельзя быть избегать. Мягкие ферриты есть отличительные в то они есть ионные соединения и имеют есть удельное сопротивление несколько порядков величины высший чем тот из металлический мягкий магнитный материалы. Поэтому, для применений с частота до 1 МГц, мягкие ферриты есть лучшие выборы с уважение к энергия потери. Главный недостаток для мягкие ферриты есть что БС есть относительно низкий Два вид из большинство общее мягкое ферриты есть Mn-Zn ферриты ((Mn, Zn)Fe2O4) и Ni-Zn ферриты ((Ni, Zn)Fe2O4). Mn-Zn ферриты are обычно используемые ниже 1 МГц, в то время, как Ni-Zn ферриты can be used at much выше частоты, but the BS and проницаемость для последний есть ниже.
К заключение, мягкий магнитный материалы чувствительный к внешний магнитный поля, это функция делает их незаменимый для многих применений особенно в в области из электрический инженерный, такой как трансформаторы, электрические двигатели, беспроводные зарядные, мощность электронные устройства, и т.д. Для а хороший мягкий магнит%2с его насыщения поток плотность%2с проницаемость%2с удельное сопротивление%2с и Кюри температура должен быть как высокий как возможный%2с когда его его коэрцитивность и магнитострикция коэффициент должен быть как низкий как возможный есть нет один один вид мягкий магнитный материалы то может бить все те другие в все аспекты of производительность выбор большинство подходящий материал, a компромисс между стоимость, железо убыток, насыщение Флюс плотность, И Проницаемость должен быть сделано.
Iron and low carbon steels have excellent saturation flux density, but their resistivities are low, limiting their usage for dynamic application. Various alloying elements can be added into iron to optimize its magnetic performance in certain aspects. Fe-Si alloys have much higher resistivities than pure iron and relatively high saturation flux densities, they are widely used for transformers and electric motors operated at 50/60 Hz and take the biggest part of the whole soft magnetic materials market. Fe-based amorphous alloys perform much better than Fe-Si alloys with respect to the iron losses and can be operated at higher frequencies, but the cost is also higher. Fe-Co alloys present the highest value of saturation flux density. With the same output power/torque, the electric machines made by Fe-Co alloys can have smaller size and less mass. Fe-Ni alloys, Co-based amorphous alloys and Fe-based nanocrystalline alloys are the softest magnetic materials, because both the values of magneto-crystalline anisotropy and magnetostriction coefficient for them can be tuned to near zero simultaneously. Among these, Fe-based nanocrystalline alloys have the highest saturation flux density, they are one kind of the most promising soft magnetic materials. SMCs or powder cores will perform better at higher frequencies than the other metallic soft magnetic materials in the form of thin strip because the particles are separated by insulating layers so the eddy current effect can be inhibited a lot. The drawbacks of SMCs are the low permeability and high hysteresis loss. Soft ferrites have resistivities several orders of magnitude higher than metallic soft magnetic materials, as a result, they are for now the best choice for operating frequencies near or above 1 MHz, but their saturation flux densities are low. Some specialists believe that in some applications soft ferrites may be replaced by SMCs to reduce the size and mass of the high-frequency devices if the processing technology for SMCs can be improved.
