Magnet degaussing packaging

The so-called degaussing, in fact, the magnetism does not disappear, but the magnetic field distribution of the magnet is changed by the magnetic material.
The degaussing packaging is generally isolated by iron sheet, and the six sides inside the box are fixed, then wrapped with pearl cotton, and then packed in cartons. For some magnets with weak magnetic properties, they can pass the security check of airlines. Some magnetic isolation materials sold on the market can also play a better degaussing effect. The strong magnet can be reassembled to reduce the magnetism of the strong magnet, so that the strong magnet can pass the airline's security check and be brought on the plane.
The principle of magnetic isolation is to shield the magnetic field, which refers to a stable magnetic field or a low-frequency magnetic field. It mainly depends on the magnetic field circuit. If the box is made of high-permeability magnetic material, it will pass out of the box.The "magnetic lines" are concentrated in the box material to form a closure, so that the magnetic lines leaking out of the box are greatly reduced. In order to achieve magnetic shielding, the higher the permeability of the material, the better; the same material, the thicker the better; the same material and thickness, the more layers, the better. In addition, the magnet should be placed in the center of the shielding box to avoid more concentrated magnetic lines on one side and more leakage.

If you want to shield the high-frequency magnetic field, it is to use a method: with a good conductive material such as metal, using a high-frequency magnetic field to form an alternating eddy current on it, forming an opposite magnetic field to cancel the original magnetic field, essentially two magnetic fields Superposition, cancel each other outside the shield, and synthesize a new magnetic circuit inside the shield. Regarding the second point, the material is magnetized. Magnetic materials are always magnetized in a magnetic field, but except for hard magnetic materials, once the external magnetic field is removed, the magnetism will immediately follow and eliminate. Therefore, if the shielding material is made of hard magnetic material to form a new independent magnetic field, the effect will be affected. This is why the shielding can only use soft magnetic materials. (If you ask, since the soft magnetic material will also be magnetized in the magnetic field, how to complete the shielding? This is because the soft magnetic material is magnetized, and the resulting new magnetic field strength, completely according to the external original field strength and change, and then according to the aforementioned high-frequency magnetic field shielding principle, phase and achieve "shielding". "Magnetic lines" is the image of the statement, the essence is the superposition of the field.) Magnetic shielding in vacuum, because air is a paramagnetic substance, the magnetic permeability is slightly greater than the vacuum, so in theory, the effect of magnetic shielding in vacuum is better than that in air, but the effect is minimal in engineering. Because the ratio of the relative vacuum permeability of paramagnetic substances and diamagnetic substances (that is, the relative permeability) is almost 1, which is at most a few thousandths of the difference. The relative permeability of magnetic materials (ferromagnetic substances) can be in the hundreds, even over 10,000 or over 100,000. Therefore, the existence of paramagnetic substances and diamagnetic substances is often not considered in engineering.