Does 316L stainless steel fiber have ferromagnetism?

316L stainless steel fibers typically have ferromagnetism. This is fundamentally different from its raw materials, as the manufacturing process changes its internal microstructure.

316L stainless steel is paramagnetic austenite at room temperature. However, during the cold drawing process of making fibers, severe plastic deformation can induce some austenite to transform into martensite, which is ferromagnetic.

The volume fraction of soft magnetic martensite phase in 316L stainless steel fibers with a diameter of 12 μm can reach as high as 62%. This means that its ferromagnetism is quite significant.

In addition, the finer the fibers, the more severe the cold drawing deformation, and the more martensite is produced. For example, the magnetic properties of 8 μ m fibers may be 3 to 6 times higher than those of 12 μm and 20 μm metal fibers. This type of magnetism also exhibits anisotropy, with stronger magnetism along the fiber axis.

However, this processing induced ferromagnetism is not permanent. By conducting annealing heat treatment at a specific temperature, martensite can be reversed to austenite, significantly reducing or eliminating the magnetic properties of metal fibers.