KM bearing introduces the reason of stainless steel tape magnetism for you
People often think that the magnet adsorption stainless steel, to verify its quality and authenticity, not attract non-magnetic, that is good, genuine; magnetic, that is counterfeit. In fact, this is a very one-sided, unrealistic way of identifying the wrong.
There are many types of stainless steels, which can be divided into several types according to their structure at room temperature:
1. AUSTENITIC type: 304,321,316,310, etc.
2. MARTENSITE or ferrite type: 430,420,410, etc.
AUSTENITIC type is non-magnetic or weak magnetic, martensite or ferrite is magnetic.
Most of stainless steel used as decorative tubesheet is austenitic 304 material, generally speaking, it is non-magnetic or weak magnetic, but it may also be magnetic because of the chemical composition fluctuation caused by smelting or different processing conditions, but this can not be regarded as a 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 composition segregation or improper heat treatment during smelting, a small amount of martensite or ferrite in austenitic 304 stainless steel can be formed. Thus, 304 stainless steel will have a weak magnetic.
In addition, 304 stainless steel after cold-working, the structure will be transformed to Martensite, cold-working deformation, martensite transformation, the more the steel magnetic. As the same batch of steel strip, 76 tubes were produced without obvious magnetic induction, and 9.5 tubes were produced. Because of the bigger deformation of cold bending, the deformation of square tube was more obvious than that of round tube.
In order to completely eliminate the magnetism of 304 steel caused by the above reasons, the stable AUSTENITE can be recovered by high temperature solid solution treatment, and then the magnetism can be removed.
In particular, as a result of the above reasons, 304 stainless steel magnetic, and other materials of stainless steel, such as 430, carbon steel magnetic is not the same level, that is to say, 304 steel magnetic is always showing a weak magnetic.
This tells us that if the stainless steel strip is weak magnetic or not magnetic at all, it should be judged as 304 or 316 material; if it is the same as carbon steel, it shows strong magnetism, because it is not 304 material.In order to completely eliminate the magnetism of 304 steel caused by the above reasons, the stable AUSTENITE can be recovered by high temperature solid solution treatment, and then the magnetism can be removed