Determined by the characteristics of the magnet, if it is interpreted in terms of atomic current, the magnetic field generated by the current magnetizes other objects, the magnetized objects generate electric fields, and the electric fields interact to generate forces. Matter is mostly composed of molecules, which are composed of atoms, which in turn are composed of nuclei and electrons. Inside the atom, the electrons are constantly spinning and rotating around the nucleus. Both movements of electrons are magnetic. However, in most materials, the direction of electron movement is different and disorderly, and the magnetic effects cancel each other out. Therefore, most substances do not appear magnetic under normal conditions. Ferromagnetic materials such as iron, cobalt, nickel, or ferrite are different. The electron spins inside them can be arranged spontaneously in a small range to form a spontaneous magnetization region. This spontaneous magnetization region is called a magnetic domain. After the ferromagnetic substance is magnetized, the internal magnetic domains are aligned neatly and aligned in the same direction, so that the magnetism is strengthened to form a magnet. The process of attracting iron to a magnet is the process of magnetizing the iron block. The magnetized iron block and the magnet have different polarities, and the iron block firmly "sticks" with the magnet. We say that magnets are magnetic.
Whether a magnet can pick up something is related to the magnetic permeability of the sucked thing, and the magnetic permeability is related to the magnetic domain. Of the various elements in nature, nickel has the highest magnetic permeability, then cobalt, and then iron. , Other materials such as copper also have a certain magnetic permeability, but very low, so that we can not feel anything, not iron-containing things can be attracted by the magnet, stainless steel is an alloy that is based on iron and added chromium and Nickel such as 1Cr13 is added with Cr, 310 stainless steel, that is, Cr25Ni20Si2 is added with Cr and Ni, and Si, 304 stainless steel is added with Cr, Ni, and Ti. This will change the original magnetic domain arrangement and reduce the permeability. Even our hands can't feel it, so we don't feel it. According to the same principle, we can also use alloys to make alloys with very high magnetic permeability.
People often use magnets to attract stainless steel to verify its pros and cons. Do not attract non-magnetic, it is considered good, otherwise, it is considered a fake. In fact, this is an unrealistic method of discrimination. People who have been operating stainless steel for more than ten years generally know that relying on the traditional method of judging stainless steel is likely to suffer. According to them, there are many types of stainless steel, which can be divided into austenite type and martensite or ferrite type according to the structure at room temperature. The austenite type is non-magnetic or weakly magnetic, and the martensite or ferrite type is magnetic. However, this is not necessarily the case. If it is usually used as a decoration tube sheet, the austenitic 304 material is generally non-magnetic, but it may also appear magnetic due to fluctuations in chemical composition caused by smelting or different processing conditions, which cannot be considered counterfeit or unqualified. In addition, 304 stainless steel undergoes cold working, and the structure will also be transformed to martensite. The greater the degree of cold working deformation, the more martensite transformation, the greater the magnetic properties of the steel. On the contrary, the 200-series stainless steel with a lower quality is likely to be non-magnetic, and it is very wrong to judge it to be a genuine stainless steel.