There are many types of stainless steel, room temperature according to the organizational structure can be divided into several categories:
1, austenite type: such as 304, 321, 316, 310, etc.;
2, martensite or iron element type: such as the 430, 420, 410, etc;
Austenite size is non-magnetic or weakly magnetic, and martensite and ferrite are magnetic.
Often used as decorative tube plates mostly austenite size of 304 stainless steel material, generally non-magnetic or weakly magnetic, but caused by smelting chemical composition may also appear different magnetic fluctuations or processing status, but it cannot be considered a counterfeit or substandard, what reason is this?
As mentioned above austenite is non-magnetic or weakly magnetic, and martensite and ferrite are magnetic, due to improper smelting composition segregation or heat treatment, which can cause a small amount of martensite in the austenitic stainless steel 304 or ferrite organization. In this way, will be with weak magnetic 304 stainless steel.
In addition, 304 stainless steel after cold working, the organization structure will be to the martensitic transformation, the greater the degree of cold deformation, martensitic transformation, the magnetic steel. As a number of steel strips, the production of Φ 76 tubes, no obvious magnetic induction, Φ 9.5 tube production. Because ling bending deformation is magnetically sensitive to some apparently, rectangular tube production due to the deformation is bigger than the circular tube, especially the Angle, more intense magnetic more obvious deformation.
To eliminate the causes of 304 magnetic steel treated by high-temperature solid solution stability returns austenitic organization, thus eliminating magnetism. In particular, due to the above causes of 304 stainless steel magnetic, and other stainless steel materials, such as 430, carbon steel magnetic completely is not the same level, that is to say, 304 magnetic always shows the weak magnetic steel.
This tells us, that if the stainless steel is weakly magnetic or completely without magnetic, should distinguish the material for 304 or 316; If the magnetic with carbon steel, shows strong magnetic, 304 for judging is not material.