Permanent magnet process
Just like the type of magnetic steel rod you usually see, a permanent magnet is an object that can retain a certain residual magnetization after removing the external magnetic field. To achieve zero residual magnetization and complete elimination of magnetism for such an object, a reverse magnetic field must be applied. The reverse magnetic field required for complete demagnetization of ferromagnetic materials is called the Coercivity of ferromagnetic materials. Both steel and iron are ferromagnetic, but their Coercivity is different. Steel has a larger Coercivity, while iron has a smaller Coercivity. This is because during the steelmaking process, elements such as carbon, tungsten, and chromium are added to iron, resulting in the production of carbon steel, tungsten steel, chromium steel, etc. The addition of elements such as carbon, tungsten, and chromium results in various non-uniformities within steel at room temperature, such as uneven crystal structure, internal stress, and magne