The angled part of the stainless steel plate has intense magnetism due to deformation

 　　Why does stainless steel plate also have magnetism? People often use magnets to adsorb stainless steel plates to verify their quality and authenticity. They believe that they are good and genuine without magnetism; If the inhaler has magnetism, it is considered a counterfeit. In fact, this is a very one-sided and unrealistic method of identifying errors. There are various types of stainless steel plates, which can be divided into several categories according to their organizational structure at room temperature: 1. Austenitic type: such as 304, 321, 316, 310, etc; 2. martensite or ferrite type: such as 430, 420, 410, etc; Austenite is nonmagnetic or weakly magnetic, while martensite or ferrite is magnetic. The stainless steel plates commonly used for decorative tube sheets are mostly austenitic 304 materials, which are generally non magnetic or weakly magnetic. However, due to fluctuations in chemical composition or different processing conditions caused by smelting, magnetism may also occur. However, this cannot be considered as counterfeit or unqualified. What is the reason for this? As mentioned above, austenite is nonmagnetic or weakly magnetic, while martensite or ferrite is magnetic. Due to component segregation or improper heat treatment during smelting, a small amount of martensite or ferrite will be formed in austenitic 304 stainless steel plate. In this way, 304 stainless steel plates will have weak magnetism. In addition, after cold processing, the microstructure of 304 stainless steel plate will also transform to martensite. The greater the cold deformation, the more martensite transformation, and the greater the magnetic properties of the steel. Like a batch of steel strips, production Φ 76 tubes, no obvious magnetic induction, production Φ 9.5 Tube. Due to the large deformation caused by cold bending, the magnetic induction is more pronounced. The production of square rectangular tubes has a greater deformation than circular tubes, especially in the angled part, which causes more intense deformation and more pronounced magnetic induction. To completely eliminate the magnetism of 304 steel caused by the above reasons, stable austenite structure can be restored through high-temperature solid solution treatment, thereby eliminating magnetism. It should be noted that the magnetism of 304 stainless steel plate caused by the above reasons is completely different from that of other materials such as 430 and carbon steel, which means that the magnetism of 304 steel always shows weak magnetism. This tells us that if the stainless steel plate has weak magnetism or no magnetism at all, it should be classified as 304 or 316 material; If it exhibits strong magnetism similar to carbon steel, it is judged that it is not made of 304 material.