Why does stainless steel decorative tube also have magnetic?

It is usually thought that magnets adsorb stainless steel decorative tubes and verify their quality and authenticity. If they are not attracted or magnetized, they think it is good and sincere. If the attractor is magnetic, it is considered false. In fact, this is a very one-sided, unrealistic and wrong way of distinguishing. There are many types of stainless steel decorative pipes, which can be divided into several categories according to their organization structure at room temperature: 1. Austenite: such as 304, 321, 316, 310, etc. 2. Martensitic or ferritic type: such as 430, 420, 410, etc. Austenite is non-magnetic or weakly magnetic, and martensite or ferrite is magnetic. Stainless steel decorative tubes, usually used as decorative tubes, are mostly made of austenitic 304 material. In general, they are non-magnetic or weakly magnetic. However, fluctuations in the chemical composition due to melting or different processing conditions may also produce magnetism, but this cannot be a reason to consider it counterfeit or substandard. It is pointed out that austenite is non-magnetic or weakly magnetic, and martensite or ferrite is magnetic. Due to improper segregation or heat treatment, a small amount of martensite or ferrite structure is produced during smelting. In this way, there will be weak magnetism in the 304 stainless steel decorative tube. In addition, 304 stainless steel decorative pipe after cold processing, its organizational structure will also change to martensite. The greater the degree of cold working deformation, the more martensitic transformation, the greater the magnetic properties of steel. Just like producing a batch of steel strips, a Φ76 steel pipe is produced. There is no significant magnetic induction, resulting in a Φ9.5 tube. Due to the large bending deformation, the magnetic induction intensity is more obvious. The deformation of square rectangular tube is larger than that of round tube, especially the corner, the deformation is stronger and the magnetism is more obvious. 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, thus eliminating the magnetic properties. In particular, it should be pointed out that the magnetic properties of 304 stainless steel decorative tubes caused by the above reasons are not at the same level as the magnetic properties of other stainless steel decorative tubes, such as 430 and carbon steel, which means that the magnetic properties of 304 steel are always weak. It's magnetic.