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Magnetic properties of stainless steel

People often think whether the magnet adsorption stainless steel material can verify stainless steel is real or not. Real stainless can not adsorption the magnet, while a magnetic suction is considered is a fake stainless. In fact, this is a very one-sided, kind of practical error identification method.

There are many kinds of stainless steel, which can be divided into several types according to the structure in the normal temperature:

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

2. martensite or ferrite stainless: such as 430, 420, 410, etc.;

The austenite is not magnetic or weak magnetic, the martensite or ferrite is magnetic.

Usually used as a decoration tube plate the majority of stainless steel is Austenitic 304, generally speaking is non-magnetic or weakly magnetic, but because the smelting caused by fluctuations in chemical composition or processing status of the different magnetic properties may also appear, but this does not think is fake or substandard, it is what reason?

The austenite is not magnetic or weak magnetic field, while the martensite or ferrite is magnetic, due to the melting of the composition segregation or improper heat treatment, will cause a small amount of martensite or ferrite in Austenitic 304 stainless steel. In this way, the 304 stainless steel will have a weak magnetic.

In addition, 304 stainless steel after cold processing, the structure of the organization will be transformed into martensite, the greater the degree of cold deformation, the more martensite transformation, the greater the magnetic steel. Like a lot of the strip, with 76 production tube, no obvious induction, Phi 9.5 tube production. Because of cold bending deformation of large induction is obvious, producing rectangular tube due to deformation than the cylinder, especially the angular part of the more intense magnetic more obvious deformation.

To completely eliminate the above reasons, the magnetic properties of the 304 steels can be recovered by high temperature solid solution treatment to restore the stability of the austenite structure, thereby eliminating the magnetic.

In particular, it is proposed that the magnetic properties of 304 stainless steel, and other materials of stainless steel, such as 430, carbon steel is completely not the same level, that is, the magnetic properties of the 304 steel always show weak magnetic.

This tells us that if the stainless steel with weak magnetic or completely non magnetic, should be identified as 3-4 or 316 material; if carbon steel with the same, showing a strong magnetic, because the distinction is not 304. 

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