Why are 304, 316 stainless steel pipe fittings magnetic

In real life, most people think that stainless steel is not magnetic, and it is unscientific to use magnets to identify stainless steel. People often think that magnets absorb stainless steel materials to ensure their quality and authenticity. They are not attractive and non-magnetic. They are considered to be good and genuine; if they are magnetic, they are thought to be counterfeit products. This is just an extremely one-sided and impractical method of identifying errors. There are many types of stainless steel, which can be divided into several categories according to the organizational structure at room temperature

1. Austenite type such as 304, 321, 316, 310, etc.;

2. Martensite or ferrite type such as 430, 420, 410, etc.; Austenitic type is non-magnetic or weakly magnetic, and martensite or ferrite is magnetic. Most of the stainless steel is commonly used for decorative tube sheets is austenitic 304, which is generally non-magnetic or weakly magnetic. However, due to chemical composition fluctuations or different processing conditions caused by smelting, magnetism may also appear, but this cannot be thought of as What is the reason for counterfeit or unqualified? As noted above, austenite is non-magnetic or weakly magnetic, while martensite or ferrite is magnetic. Due to component segregation or improper heat treatment during smelting. A small amount of martensite or ferrite in austenitic 304 stainless steel will be caused. Body tissue. In this way, 304 stainless steel will have weak magnetic properties. Also, after 304 stainless steel is cold worked, the structure will be converted into martensite. The greater the degree of cold working deformation, the greater the transformation of martensite and the greater the magnetic properties of the steel. Like a batch of steel belts, Φ76 tubes are produced without obvious magnetic induction, and Φ9.5 tubes are produced. Because the bending deformation is larger, the magnetic induction is more obvious, and the deformation of the rectangular square tube is larger than that of the round tube, especially the corner part, the deformation is more intense and the magnetism is more obvious. To eliminate the hypnotic properties of 304 steel caused by the above reasons, the austenite structure can be restored and stabilized by high-temperature solution treatment, thereby eliminating the magnetic properties. In particular, the magnetism of 304 stainless steel caused by the above factors is not at the same level as other materials of stainless steel, such as 430 and carbon steel. That just says, the magnetism of 304 steel always shows weak magnetism. This shows us that if the stainless steel is weakly magnetic or not at all, it should be judged as 304 or 316; if it is the same as carbon steel, it shows strong magnetism, because it is judged as not 304. Both 304 and 316 are austenitic stainless steel and are single-phase. It is weakly magnetic.