Why is the 304 stainless steel strip magnetic?

According to a salesperson in Shenzhen Yitian Metal, customers often think that the magnet is adsorbing stainless steel to verify its quality and authenticity. If it does not attract or magnetize, it is considered to be good and genuine; if it is magnetized, it is considered to be genuine. It is a fake. In fact, this is an extremely one-sided and very impractical method of identifying errors. There are many types of stainless steel, which can be divided into several categories according to the organizational structure at room temperature:

One: Austenite type: such as 304, 201, 316, 301, etc.;

Two: martensite or ferrite type: such as 430, 420, 410, etc.; austenite type is non-magnetic or weakly magnetic, and martensite or ferrite is magnetic. The stainless steel usually used as decorative tube sheet is mostly austenitic 304 steel strip. Generally speaking, it is non-magnetic or weak magnetic. However, due to chemical composition fluctuations caused by smelting or different processing conditions, magnetism may also appear, but this cannot be considered Is it counterfeit or unqualified, what is the reason? As mentioned above, austenite is non-magnetic or weakly magnetic, while martensite or ferrite is magnetic. Because of composition segregation or improper heat treatment during smelting, a small amount of martensite or iron in austenitic 304 stainless steel will be formed. Body arrangement. In this way, 304 stainless steel strip will have weak magnetic properties. In addition, 304 stainless steel through cold working, the arrangement structure will also be transformed into martensite, the greater the degree of cold working deformation, the greater the transformation of martensite, and the greater the magnetic properties of the steel. Like a batch of steel belts, Φ76 tubes are produced without significant magnetic induction, and Φ9.5 tubes are produced. Because the bending deformation is larger, the magnetic induction is more pronounced. The square rectangular tube produced has a larger deformation than the round tube, especially in the corners, the deformation is more severe and the magnetism is more pronounced. In order to completely eliminate the magnetic properties of 304 steel formed by the above-mentioned reasons, the austenite arrangement can be stabilized and stabilized by high-temperature solution treatment, and then the magnetic properties can be eliminated. Of 304Stainless steel stripMagnetism is mainly caused by the friction between the work roll and the stainless steel belt during rolling.