2024-11-22
Stainless steel-Why 304 stainless steel pipe is magnetic
It is generally believed that austenitic stainless steel (represented by 304) is non-magnetic, but sometimes it may have certain weak magnetic properties, while ferrite (mainly 430, 409L, 439 and 445NF, etc.) and martensite (represented by 410 Represented) are usually magnetic.Some steel grades in stainless steel welded pipes (such as 304, etc.) are classified as "non-magnetic stainless steel", which just means that their magnetic index is lower than a certain value. In other words, stainless steel is more or less magnetic. . When the stainless steel welded pipe is produced, it is extruded through the mold, and the iron molecules in the mold will more or less penetrate into the surface of the pipe, resulting in weak magnetism.In addition, as mentioned earlier, austenitic stainless steel is non-magnetic or weakly magnetic, while ferrite and martensite are magnetic. However, due to composition segregation or improper heat treatment during smelting, a small amount of martensite will also be formed in austenitic stainless steel. Tentenite or ferrite structure, such austenitic stainless steel will produce weak magnetism.In addition, after austenitic stainless steel is cold-worked, part of the austenite structure will also transform into martensite. The greater the cold-working deformation, the more transformed martensite structure, and the stronger the magnetism of stainless steel.