The application of soft magnetic materials in industry began at the end of the 19th century. With the rise of electric power and telecommunication technology, low carbon steel was used to manufacture motors and transformers, and fine iron powder, iron oxide, fine iron wire, etc. were used in the magnetic core of the inductance coil in the telephone line.
Common magnetic properties of soft magnetic materials
Saturation magnetic induction intensity bs: Its size depends on the composition of the material, and its corresponding physical state is that the magnetization vectors inside the material are neatly arranged. Residual magnetic induction intensity br: is the characteristic parameter on the hysteresis loop, the b value when h returns to 0. Squareness ratio: br∕bs Coercive force hc: It is a quantity that indicates the difficulty of magnetization of the material, and depends on the composition and defects of the material (impurities, stress, etc.). Magnetic permeability μ: is the ratio of b to h corresponding to any point on the hysteresis loop, which is closely related to the working state of the device. Initial permeability μi, maximum permeability μm, differential permeability μd, amplitude permeability μa, effective permeability μe, and pulse permeability μp. Curie temperature tc: The magnetization of ferromagnetic substances decreases as the temperature increases. When a certain temperature is reached, the spontaneous magnetization disappears and becomes paramagnetic. The critical temperature is the Curie temperature. It determines the upper limit temperature at which magnetic devices work. Loss p: hysteresis loss ph and eddy current loss pe p = ph + pe = af + bf2+ c pe ∝ f2 t2 / , ρ decreases, the method of hysteresis loss ph is to reduce coercive force hc; the method to reduce eddy current loss pe is Thinning the thickness t of the magnetic material and increasing the resistivity ρ of the material. The loss of the core in free still air is related to the temperature rise of the core as: Total power dissipation (mw)/surface area (cm2)
