Classification of soft magnetic alloy materials

- Aug 01, 2019-

There are many kinds of soft magnetic alloys, which can be divided into electromagnetic pure iron (industrial pure iron), ferro-silicon alloy, ferro-nickel alloy, ferro-aluminum alloy, ferro-silicon alloy and ferro-cobalt alloy, etc. If the magnetic characteristics of the alloy can be divided into high magnetic saturation alloy, high permeability alloy, high rectangular ratio alloy, electrical steel, constant permeability alloy, high delta B alloy, corrosion resistant soft magnetic alloy and thermal magnetic compensation alloy. According to the internal structure of the alloy, it can be divided into crystalline soft magnetic alloy, amorphous soft magnetic alloy and nanocrystalline soft magnetic alloy.


Electromagnetic pure iron carbon content less than 0.04% iron and mild steel, including electrical pure iron, dielectric iron and carbonyl iron. It is characterized by saturation magnetization up to 2.15t, low price and good processing performance. However, the low resistivity and large eddy current loss in alternating magnetic field are only suitable for static use. It is mainly used as magnetic conductor for electromagnet core, pole shoe, relay and loudspeaker, and magnetic shield cover.


Ferrosilicon alloy containing 0.5% ~ 4.8% silicon content, generally in the form of thin plate production, including hot rolled silicon steel, non-oriented cold rolled silicon steel and oriented cold rolled silicon steel. The addition of silicon to iron can eliminate the serious magnetic aging phenomenon of pure iron. With the increase of silicon content, although the magnetic saturation (saturation magnetization intensity) decreases, its resistivity and permeability increase, and the force and eddy current loss decrease, thus expanding its application in the field of communication. Due to its low price, it has become the leading product of soft magnetic alloy, widely used in power industry, mechanical and electronic industry and instrument industry as transformer, power amplifier, inductance coil, stator and rotor of motor, etc. Generally, the electromagnetic pure iron and silicon steel sheet collectively referred to as electrical steel.


The iron aluminum alloy with the content of 6% ~ 16% has good soft magnetic properties, not only high permeability and resistivity, but also high hardness and good abrasion resistance. But its properties are brittle, difficult to roll and press, and its use is affected. The alloy is mainly used for magnetic head core and small transformer, magnetic amplifier, relay core, etc.


Ferrosilicon-aluminum alloy the addition of silicon to binary ferro-aluminum alloy can make the magnetocrystalline anisotropy K1 and magnetostrictive lambda s tend to zero at the same time, resulting in the ferrosilicon-aluminum soft magnetic alloy with high magnetic properties. Its typical composition is 9.6% silicon, 5.4% aluminum, the rest is iron. It is characterized by extremely high hardness, high magnetic saturation (about 1T), high permeability and high resistivity. The disadvantage is that the magnetic fluctuation of the composition is very sensitive, brittle, poor processing performance. The alloy is mainly used for audio and BBB 0 heads.


Ferronickel alloy the ferronickel alloy with the nickel content of 30% ~ 90% is often called permo alloy. In this composition range, soft magnetic alloys with different magnetic properties, such as high permeability, constant permeability and constant moment, can be obtained by adding appropriate alloying elements and adopting appropriate technology. Permo alloy has high plasticity and can be cold rolled into 1 micron ultra-thin band, which is the most widely used soft magnetic alloy. It can be used for iron core and magnetic shield under weak magnetic field, pulse transformer and inductance core with low remanence and constant permeability, high rectangular ratio alloy, thermo-magnetic compensation alloy and magnetostrictive alloy, etc. The disadvantage is that it is expensive and the loss is large when used in ultra-high frequency magnetic field.


Iron-cobalt alloy with cobalt content of 27% ~ 51% has the highest saturation magnetization. For example, the saturation magnetic induction intensity of 35co-fe alloy reaches 2.43t, 13% higher than that of electromagnetic pure iron. Binary fe-co alloy has poor mechanical properties and low resistivity, and the addition of proper amount of chromium and vanadium can improve the processing performance, which is most suitable for high saturation magnetic sensing material and high performance soft magnetic material, mainly used for pole boots, motor rotor and stator, transformer core, etc.


An alloy, also known as amorphous metal or metallic glass, that has no long process and no crystalline grains. Amorphous alloys with soft magnetic properties have the characteristics of high permeability, low coercivity, insensitivity to stress, corrosion resistance and high strength. In addition, its high resistivity can be used for high frequency. The disadvantage is that it will occur at a lower temperature crystallization, and at a lower temperature will occur structural relaxation, magnetic changes, so the operating temperature should not be too high, should not exceed 100 ~ 150℃. There are two main types of amorphous soft magnetic alloys: metal-metal type and metal-metal type. The former is more widely used, and it is divided into cobalt base, iron base and iron nickel base. Amorphous soft magnetic alloys have different magnetic properties and can be used as substitutes for other soft magnetic materials.


Ultramicrystalline soft magnetic alloy is a new soft magnetic alloy discovered since 1980s. It is composed of crystalline phase and amorphous grain boundary phase less than 50nm. It has better comprehensive magnetic properties than crystalline and amorphous alloy, not only with high permeability, low coercivity and small loss, but also with high saturation magnetic sensitivity and good stability. For example, FeZrB and FeCuNbSiB are mainly iron-based ultrafine alloys. Like permo alloys with high nickel content, different heat treatment processes can be used to obtain different magnetic properties.