In life, we often use whether the tube is magnetic to judge the quality of stainless steel, but in fact, this method is very unscientific, such as our common zinc tube alloy, tube copper alloy, etc., can generally imitate the appearance of stainless steel color, and there is no tube magnetic, easy to be mistaken for rust steel, even if it is 304 steel that we often use tubes at present, after cold processing, There will also be different degrees of tube magnetism, so you can not judge the quality of stainless steel by whether there is a magnetic tube, then why 304 stainless steel pipes will be magnetic.
Under normal circumstances, stainless steel tubes can be divided into two categories according to the organization structure at room temperature, one is austenitic stainless steel tubes, such as 304,321 tubes, 316 tubes, 310 tubes, etc., the other is martensitic or ferritic stainless steel tubes, such as 430,420 tubes, 410 tubes, etc., and austenitic stainless steel tubes are non-magnetic or weakly magnetic, martensitic or ferritic tubes are magnetic. So 304 stainless steel pipe is non-tube magnetic or with if magnetic.
And we often say that 304 stainless steel is non-magnetic stainless steel, the tube refers to its magnetic index is lower than a certain value, that is, the tube means that stainless steel is generally more or less with a certain tube magnetism, the premise of the austenitic stainless steel tube is non-magnetic or weak magnetic, and the ferritic and martensitic stainless steel is with magnetic tube. This is due to improper segregation of components or heat treatment tubes during smelting, resulting in a small amount of martensitic or ferritic structure in austenitic 304 stainless steel, so that there will be weak magnetism in 304 stainless steel tubes, and the tube is 304 stainless steel after cold processing, the structure of the tube will also be transformed to martensitic, and with the cold tube processing deformation, the more martensitic conversion tubes, The stronger the magnetic tube will be.
Therefore, the magnetic properties of the material are determined by whether the molecular arrangement of the tube is regular, as well as the isotropic tubular properties of the electron spin, which can be considered to be the physical properties of the tube, while the corrosion resistance of the material is determined by the chemical composition of the material, which is the chemical properties of the tube material, and has nothing to do with whether the material is magnetic.
