Why does stainless steel flange carry magnetism?

We often use magnets to adsorb stainless steel flange, to verify their merits and demerits, without magnetic absorption, which is considered good and genuine; if the sucker is magnetic, it is considered to be fake. In fact, this is a very one-sided, unrealistically wrong way of identifying. There are many kinds of stainless steel, which can be classified into several types according to their organizational structure at room temperature.

　　1. Austrian body: 304, 321, 316, 310, etc.

　　2. martensite or ferrite type: 430, 420, 410, etc.

　　The austenite type is nonmagnetic or weakly magnetic, and martensite or ferrite is magnetic.

　　Most Forging 304 Stainless Steel Socket Flanges used as decorative tubesheet is 304 austenitic material. Generally speaking, it is non-magnetic or weak magnetic. However, because of the fluctuation of chemical composition or different processing conditions caused by smelting, it may also appear magnetic. But this can not be considered as fake or unqualified. What is the reason?

　　As mentioned above, austenite is non-magnetic or weak magnetic, while martensite or ferrite is magnetic. Due to the segregation of composition or improper heat treatment during smelting, a small amount of martensite or ferrite in Austenitic 304 stainless steel flange will be formed. In this way, 304 stainless steel flange will have weak magnetism.

　　In addition, 304 stainless steel flange after cold processing, the structure will also be transformed to martensite, the greater the deformation degree of cold processing, the more martensite transformation, the greater the magnetism of steel. Like a batch of steel strips, produce Φ 76 tubes, without obvious magnetic induction, produce Φ 9.5 tubes. Because the cold bending deformation is larger, the magnetic induction is more obvious. Because the deformation of square rectangular pipe is larger than that of circular pipe, especially in the corner part, the deformation is more intense and the magnetism is more obvious.

　　If the stainless steel flange is weak or completely non-magnetic, it should be distinguished as 304 or 316 material; if it is the same as carbon steel, it shows strong magnetism, because it is not 304 material.