Magnet adsorption sewage treatment

It is often thought that the magnet adsorbs the sewage treatment material to verify its quality and authenticity. If it does not absorb non-magnetic materials, it is considered as good and the goods are real. If it has magnetism, it is considered as fake. In fact, this is an extremely one-sided and impractical wrong way to distinguish.

There are many kinds of sewage treatment, which can be divided into several types according to the organizational structure at room temperature:

1. Austenite type: such as 304, 321, 316, 310, etc;

2. Martensitic or ferritic type: such as 430, 420, 410, etc;

Austenite is nonmagnetic or weakly magnetic, while martensite or ferrite is magnetic.

Generally speaking, most of the sewage treatment used as decorative tube sheet is made of 304 material of austenite type, which is generally non-magnetic or weak magnetic. However, due to the fluctuation of chemical composition or different processing state caused by smelting, magnetism may also appear, but this cannot be considered as fake or unqualified. What's the reason?

As mentioned above, austenite is non-magnetic 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 structure will be produced in Austenitic 304 sewage treatment. In this way, 304 sewage treatment will have weak magnetism.

In addition, the microstructure of 304 waste water will also change to martensite after cold working. The larger the cold working deformation, the more martensite transformation, and the greater the magnetic properties of the steel. For the same batch of steel strip, Φ 76 pipe is produced, without obvious magnetic induction, Φ 9.5 pipe is produced. Because of the large bending deformation, the magnetic induction is more obvious. Because of the larger deformation, especially the angle part, the production square rectangular tube has more intense deformation and more obvious magnetism.

In order to completely eliminate the magnetism of 304 steel caused by the above reasons, the stable austenite structure can be recovered by high temperature solution treatment, so as to eliminate the magnetism.

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

This tells us that if the sewage treatment has weak magnetism or no magnetism at all, it should be judged as 304 or 316 material; if it has the same magnetism as carbon steel, it shows strong magnetism, because it is not 304 material.