People often think that magnets attract stainless steel to verify its quality. If it does not attract stainless steel, it is good and authentic; if the suction cup is magnetic, fakes are considered fake. In fact, this is an extremely one-sided, unrealistic and wrong way of identification.
There are many types of stainless steel, which can be divided into several categories according to their normal temperature structure:
1. Austenitic type: such as 304, 321, 316, 310, etc.
2. Martensite or ferrite type: such as 430, 420, 410, etc.;
Austenite is magnetic or weakly magnetic, and martensite or ferrite is magnetic.
Stainless steel usually used for decorative tube sheets is mostly made of austenitic 304, which is generally non-magnetic or weakly magnetic. However, magnetism may also appear due to fluctuations in chemical composition caused by smelting or processing conditions, but this cannot be considered fake or Unqualified, what is the reason?
As mentioned above, austenite is non-magnetic or weakly magnetic, while martensite or ferrite is magnetic. Due to segregation or improper heat treatment during smelting, a small amount of martensite or ferrite structure will appear 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 transform into martensite. The more cold working deformation, the greater the martensite transformation, the greater the magnetic force of the steel. Like a batch of steel strips, 76 tubes are produced. There is no obvious magnetic induction, and 9.5 tubes are produced. Since the deformation of the slap bend is larger, the magnetic sensation is more obvious. The square and rectangular tubes produced by Paida Bending have a greater deformation than round tubes, especially in the corner parts, where the deformation is more severe and the magnetism is more obvious.
