Stainless steel small capillaryThe manufacturer will explain to you, why is it magnetic?

People often think that magnets absorb stainless steel pipes to verify their quality and authenticity. They are not attractive and non-magnetic. They are considered to be good and genuine; if they are magnetic, they are considered to be counterfeit products. In fact, this is an extremely one-sided, unrealistic and wrong way of distinguishing. The stainless steel raw material used in the manufacture of stainless steel pipes is controlled by the oil content of the iron element in the pipe according to the type and scope of use restricted by the pipe.

There are many types of stainless steel pipes, which can be divided into several categories according to their organizational structure at room temperature:
1. Austenite type: such as 304, 321, 316, 310, etc.;
2. Martensite or ferrite type: such as 430, 420, 410, etc.;
Austenite is non-magnetic or weakly magnetic, and martensite or ferrite is magnetic.
The stainless steel pipes generally used for decoration tube sheets are mostly austenitic 304 materials, which are generally non-magnetic or weakly magnetic. However, due to the chemical composition that is formed by exercise or the processing state is different, they may also appear magnetic, 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 component segregation or improper heat treatment during tempering, a small amount of martensite or iron in the austenitic 304 stainless steel tube Body arrangement. In this way, the 304 stainless steel tube will have weak magnetism.

In addition, after 304 stainless steel pipe is cold worked, the 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 pipes are produced without obvious magnetic induction, and Φ9.5 pipes are produced. Because the bending deformation is larger, the magnetic induction is more obvious. The deformation of the square rectangular tube is larger than that of the round tube, especially the corner part, the deformation is more intense and the magnetism is more obvious. If some manufacturers want to eliminate the magnetism contained in some stainless steel pipes, they can restore the austenite structure of the pipe under the conditions of high temperature and solid solution, so as to eliminate the magnetism of the pipe.

In particular, the magnetism of the 304 stainless steel tube formed due to the above reasons is completely different from the magnetism of other materials, such as 430 and carbon steel, which means that the magnetism of 304 steel has always been weak magnetism. . This tells us that if the stainless steel tube is weakly magnetic or completely non-magnetic, it should be judged as 3-4 or 316 material; if it is the same as carbon steel, it shows strong magnetism, because it is judged to be not 304 material.