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Name: 304 stainless steel coil
There are many kinds of stainless steel, which can be divided into several types according to the structure at room temperature.
1. Austenite type: 304, 321, 316, 310, etc.
2. Martensite or ferrite type: 430, 420, 410, etc.
Austenite type is nonmagnetic or weak magnetic, martensite or ferrite is magnetic.
Most stainless steel coil 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 caused by smelting or different processing conditions, it may also appear magnetic, but this can not be considered as fake or unqualified.
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 will be formed. In this way, 304 stainless steel coil will have a weak magnetism.
In addition, 304 stainless steel coil 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, production of 76 tubes, no obvious magnetic induction, production of 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.
In order to completely eliminate the magnetism of 304 stainless steel coil caused by the above reasons, the stable austenite structure can be restored by solution treatment at high temperature, thus the magnetism can be eliminated.
In particular, the magnetism of 304 stainless steel caused by the above reasons is not the same level as that of other stainless steels, such as 430 and carbon steel. That is to say, the magnetism of 304 steel always shows weak magnetism.