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Explanation of the magnetic of stainless steel

Explanation of the magnetic of stainless steel
Update Time:2019-12-13
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It is often thought that a magnet is  used to test the quality of stainless steel. If the stailes steel is nonmagnetic, the product is genuine. If it is magnetic, the product is fake. In fact, this  is an extremely one-sided, impractical and incorrect identify method. Generally speaking, stainless steel is either magnetic or non-magetic.

Austenite stainless steel is non-magnetic or weakly magnetic, such as 201, 202,304,316 etc.martensite or ferreite is  magnetic, such as 430, 420,410 etc. However, due to component segregation or improper heat treatment during smelting. a small amount of martensite or ferrite structure will be caused in austenitic 304 stainless steel. In this way, 304 stainless steel will have weak magnetism. In addition,304 stainless steel undergoes cold working, and the structure will also be transformed to martensite. The greater the degree of cold working deformation, the more martensite transformation, and the greater the magnetic properties. Like a batch of stainless steel wires, it is made straight and has no obvious magnetic induction, but when it is bent inot a rectangle or a circle, some magnetism is generated due to the large cold bending deformation, especially the corners are more obvious.

 If you want to eliminate of the magnetic properties of the above 304 stainless steel completely, high temperature treatment can be used to restore the stable austenite structure, thereby eliminating the magnetic properties. It is particularly reminded that the magnetic properties of 304 stainless steel caused by the above reasons are completely different from the magnetic properties of other materials such as 430 and carbon steel, which means that the magnetic properties of 304 stainless steel are always weakly magnetic.