There are many types of stainless steel, at room temperature according to the organizational structure can be divided into several categories:
1, austenitic: such as 304, 321, 316, 310, etc.;
2, martensite or ferrite: such as 430, 420, 410, etc.;
Austenitic is non-magnetic or weakly magnetic, martensitic or ferritic is magnetic.
Often used as a decorative tube plate of stainless steel most of the austenitic 304 material, generally
speaking is non-magnetic or weakly magnetic, but due to the smelting caused by fluctuations in the chemical composition or processing state is not
the same may also appear magnetic, but this can not be considered a fake or unqualified, this is what
reason?
It was mentioned above that austenite is non-magnetic or weakly magnetic, while martensite or ferrite is magnetic
, due to the smelting of compositional segregation or improper heat treatment, it will result in a small amount of martensite or ferrite organization in the austenitic 304 stainless
steel. In this way, 304 stainless steel will have a slight
weak magnetic properties.
In addition, 304 stainless steel after cold processing, the organizational structure will also be transformed to martensite, cold
processing deformation degree is greater, the more martensite transformation, the greater the magnetic properties of steel. As the same
lot number of steel strip, the production of Φ76 pipe, no obvious magnetic feeling, the production of Φ9.5 pipe. Because of the bending
deformation of the larger magnetic sense will be obvious, the production of square rectangular tube because the deformation is larger than the round tube,
especially the corner part, the deformation is more intense magnetic more obvious.
To completely eliminate the magnetic properties of 304 steel caused by the above reasons, through high-temperature solid solution treatment
To restore stable austenitic organization, thereby eliminating the magnetic properties.
Specifically, the magnetic properties of 304 stainless steel due to the above reasons, and other
materials of stainless steel, such as 430, carbon steel, the magnetic properties are not the same level, which
is that the magnetic properties of 304 steel is always weak.
This tells us that if the stainless steel is weakly magnetic or completely non-magnetic, it should be identified
as 304 or 316 material; if the same as carbon steel's magnetism, showing strong magnetism, because
discerned as not 304 material.