Due to the continuous high price of nickel recently, the production cost of 304 and other Ni series stainless steel is high, so the promotion of 400 series stainless steel products with excellent corrosion resistance and attractive price is increasingly urgent. In order to reduce the production cost of downstream customers and improve the market competitiveness of end products, major stainless steel plants at home and abroad have increased the research and development and promotion of nickel-free or low-nickel stainless steel materials. Unfortunately, the inherent magnetic properties of 400 series stainless steel make many users intimidated.
In real life, most people think that stainless steel is not magnetic, and use magnets to identify stainless steel, this method 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, so they are easily mistaken for stainless steel; and even the 304 steel that we use more often at present, after cold working, there will be different degrees of magnetic properties. . Therefore, the authenticity of stainless steel cannot be judged only by a magnet.
But how did the magnetic properties of stainless steel come about?
According to the research of material physics, the magnetism of metals comes from the structure of electron spins, which belong to quantum mechanical properties and can be either "up" or "down". In ferromagnetic metals, electrons automatically spin in the same direction, while in antiferromagnetic metals, some electrons spin in a regular pattern, while neighboring electrons spin in opposite directions or antiparallel, but for triangular crystals For electrons in a lattice, since the two electrons in each triangle must spin in the same direction, the spin structure no longer exists.
Generally speaking, austenitic stainless steel (represented by 304) is non-magnetic, but may also have weak magnetic properties, while ferrite (mainly 430, 409L, 439 and 445NF, etc.) and martensite (410 (representative) are generally magnetic.
