What is magnetic? Simply put, the magnetic substance on a non-uniform magnetic field will be affected by a magnetic force. The wide variety of stainless steel at room temperature according to the organizational structure can be divided into the following categories:
1, the austenitic type: 201,202,304,316, etc.
2, martensite or ferrite: 430,420,410, etc.
The austenite type is non-magnetic or weakly magnetic, martensite or ferrite having magnetic properties.
Austenitic type 304 stainless steel is the highest range of applications, in general non-magnetic or weakly magnetic, but the smelting cause fluctuations in the chemical composition or different processing state may also produce magnetic, which is what causes it? We mentioned above, the austenite is non-magnetic or weakly magnetic, and martensite or ferrite, with a magnetic, austenitic 304 stainless steel smelting component segregation or improper heat treatment, will cause a small amount of martensite the or ferrite microstructure, such as, 304 stainless steel with a weak magnetic. In addition, 304 stainless steel after cold working, organizational structure will be transformed to martensite, the greater the cold deformation the more martensite transformation, the greater magnetic. Like batch No. of stainless steel wire, made straight branch, no significant magnetic sense, but it bent into a rectangular or circular, cold-formed large deformation and generate some of the Magnetic Angular part more obvious magnetic. Then through high temperature treatment to restore stable austenite, and can eliminate the magnetic.
Can learn from the above flume tank with 304 out why there is magnetic, and the magnetic uneven? The reason is that the sink basin body cold drawing process produced, because the tank trough is present by the sheet material through the mold at the room temperature conditions of deep drawing from the converted, by a great deal of a flat material having a three-dimensional shape of the basin body , visible deformation degree of cold working is very great and very serious, especially in the four R corner basin body material extrusion phenomenon through before we can understand in this cold working process, stainless steel internal organizational structure will be part of the Austrian 's body is transformed to martensite, the amount of deformation of the four corners of the basin body, the martensite transformation also up, thus magnetic strongest, and the straight edge of a relatively small amount of material deformation, their magnetic properties will be relatively weak, so we use magnets The test will be seen, in the R bit of the four corners of the sink basin body has a relatively large magnetic, but the pan directly at the edges of the magnetic weak, if placed on the sink panel feel magnetic.
Thus for cold working sink basin body we can not just by a magnet to determine whether the authenticity of stainless steel.