In real life, most people think that 304 stainless steel strips are not magnetic, and use magnets to identify stainless steel, which is very unscientific. First of all, zinc alloys and copper alloys can generally imitate the appearance and color of stainless steel, and they are not magnetic. magnetic. Therefore, the authenticity of stainless steel cannot be judged only by a magnet. So how does the magnetism of stainless steel come from? According to the research of material physics, the magnetism of metal comes from the structure of electron spin, which belongs to quantum mechanical properties and can be either up or down. In ferromagnetic metals, electrons automatically spin in the same direction. For electrons in a triangular lattice, the spin structure no longer exists because two electrons in each triangle must spin in the same direction. . Generally speaking, austenitic stainless steel (represented by 304) is non-magnetic, but it may also have weak magnetic properties, while ferrite (mainly 430, 4091, 439 and 445nf, etc.) and martensite (410 (representative) are generally magnetic.
The reason for the magnetic properties of 304 stainless steel may be the segregation of components during smelting or improper heat treatment, which will cause a small amount of martensite or ferrite in austenitic 304 stainless steel. In this way, 304 stainless steel will have weak magnetism.
In addition, after cold working of 304 stainless steel, the structure will also be transformed to martensite. The greater the cold working deformation, the more martensite transformation, and the greater the magnetic properties of the steel.
In order to completely eliminate the magnetic properties of 304 steel caused by the above reasons, the stable austenite structure can be restored by high-temperature solution treatment, thereby eliminating the magnetic properties.
But this kind of magnetism is completely different from the magnetism of 430 and carbon steel, which means that the magnetism of 304 steel always shows weak magnetism.