Is stainless steel magnetic?

Many client frequently use a way to prove the good or bad and fake or true of the stainless steel material. If no suction and no magnetic, that material is real. But if have suction and magnetic, that material is fake. Actually, this dialectical method is one-sided and impractical. Hope the following content can help you .

There are many kinds of stainless steel.　At room temperature, it normally divided into several categories according to the organizational structure.

1.Austenitic grade: such as 304, 321, 316, 310, etc.

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

Austenite is non-magnetic and weakly magnetic. Martensite or ferrite is magnetic. Most stainless steel is austenitic type 304 material, which is typically used as aesthetic stainless steel pipe and stainless steel plate and has either no magnetic properties or very weak magnetic properties. Sometime the magnetic property maybe will also occur, because of chemical composition fluctuations or different processing states. But this can not be considered imitation and unqualified. That is why ? We mentioned above that austenite is non-magnetic and weakly magnetic, and martensite or ferrite is magnetic. For the reason that improper segregation or heat treatment during smelting, make the austenitic 304 stainless steel have a small amount of martensitic or ferritic structure. So the 304 stainless steel have weakly magnetic. Besides, after cold processing, the organization structure of 304 stainless steel will change to martensite. The more the degree of cold working deformation, the more martensite transformation, and the greater the magnetic properties of the steel.

Such as using the same batch number of stainless steel strip, produce the pipe size Φ103, which have no obviously magnetic, and produce the pipe size Φ9.5,which have change to have obviously little magnetic because the bending deformation is large. The bending deformation of square tube is bigger than the round pipe. Especially the corner part. the more severse the deformation ,the greater the magnetic change. Because of the aforementioned factors, the magnetic properties of 304 stainless steel are, in particular, lower than those of other stainless steels like 430 and carbon steel. To put it another way, 304 stainless steel is never very magnetic.

In addition, how to have a deeper understanding of whether stainless steel is magnetic can also be analyzed from the different elements contained in stainless steel.

A quick breakdown:

First of all, stainless steel is usually not magnetic, if we must investigate the reason, it involves the knowledge of metal materials, here do not pull martensite, austenite.Simply put: nickel-free stainless steel is magnetic, and nickel-containing stainless steel is non-magnetic or weakly magnetic.

Why?

Stainless steel is a general term for a metal alloy, usually mixed with other metal materials, with the comprehensive properties of a variety of metals.For example, typical stainless steel contains more than 10% chromium, which forms a protective layer on the alloy against stains and damage.At the same time, it can resist scratches to prevent corrosion.In addition to chromium, other metals are added to stainless steel, one of which is nickel.In essence, nickel helps to enhance the protection of chromium, commonly known as the 300 series stainless steel.Stainless steel containing nickel is not magnetic, because the presence of nickel changes the physical structure of stainless steel, removing or inhibiting magnetism.However, magnetic stainless steel is also available.The 400 series stainless steel contains chromium but does not contain nickel and is magnetic.Magnetic strength can vary, and 400 series stainless steels are able to attract magnets and, in some cases, some small metals.

Does this have an impact on our use?

No impact, because at the time of manufacturing, the manufacturer has selected the appropriate stainless steel according to the requirements of use.If it has an impact on us, it is that stainless steel with more nickel can be sold at a good price when selling scrap.

Process measures to reduce permeability:

(1) Chemical composition control, obtain stable austenitic structure, adjust the permeability.

(2) Increase the material preparation process, if necessary, through solid solution treatment to redissolve martensite, δ-ferrite, carbide, etc. in the austenite matrix, so that the organization is more uniform, ensure that the permeability meets the requirements, and leave a certain margin for the post-sequence processing.

(3) Adjust the process and route, increase the solution treatment sequence after molding, and add a pickling sequence on the process route, and test the permeability after pickling to meet the requirements of μ < 1.1.

(4) Strict management procedures, according to the particularity of customer use, master the changes in the permeability of each process, and have a targeted optimization process.In addition, austenitic stainless steel for nuclear power should have a special place to avoid being placed in a strong magnetic environment.

(5) Choose the appropriate processing tools and tool materials, choose ceramic or carbide tools, to prevent the magnetic belt due to affecting the permeability of the workpiece.In the machining process, small cutting amount feed is used as far as possible to minimize the martensitic transformation induced by excessive compressive stress.

(6) degaussing of finished parts.