People often think that magnets adsorb stainless steel to verify its merits and demerits and authenticity. They do not absorb non-magnetism and are considered good and genuine. If the magnet is magnetic, it is considered to be a fake. In fact, this is an extremely one-sided and unpractical method of identifying errors.

There are many kinds of stainless steel, which can be divided into several categories according to the organizational structure at room temperature:

1. Austenitic type: such as 201, 202, 301, 304, 316, etc;

2. Martensite or ferrite type: such as 430, 420, 410, etc;

Austenite type is non-magnetic or weak magnetic, martensite or ferrite is magnetic.

Usually used as decorative tube plate stainless steel is mostly austenitic 304 material, generally speaking is non-magnetic or weak magnetic, but due to smelting caused by chemical composition fluctuations or different processing state may also appear magnetic, but this can not be considered counterfeit or unqualified, what is the reason?

The above mentioned austenite is non-magnetic or weak magnetic, and martensite or ferrite is magnetic, due to the composition of the smelting segregation or improper heat treatment, will cause a small amount of austenitic 304 stainless steel martensite or ferrite tissue. In this way, the 304 stainless steel will have weak magnetism.

In addition, 304 stainless steel after cold working, the structure will also transform to martensite, the greater the degree of cold working deformation, the more martensite transformation, the greater the magnetic properties of steel. Like the steel strip of the same batch number, Φ76 pipe is produced without obvious magnetic induction, and Φ9.5 pipe is produced. Due to the large magnetic induction of cold bending deformation, the deformation of the square rectangular tube is larger than that of the circular tube, especially the corner part, the deformation is more intense 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 solid solution treatment, so as to eliminate the magnetic properties.

In particular, the magnetism of 304 stainless steel caused by the above reasons is not at the same level as that of stainless steel of other materials, such as 430 steel and carbon steel, that is to say, the magnetism of 304 steel always shows weak magnetism.

This tells us that if stainless steel with weak magnetism or no magnetism at all, it should be distinguished as 304 or 316 material; if it is the same as the magnetism of carbon steel, it shows strong magnetism, because it is not a 304 material.