Stainless steel magnetic

Ferritic and martensitic stainless steels, due to the presence of ferrite and martensite, are ferromagnetic, i.e. they "take by the magnet".

Austenitic stainless steels present, at ambient temperature, an austenitic structure which allows them to be paramagnetic (in everyday language they are considered to be non-magnetic).

However, some austenitic stainless steels can become ferromagnetic after significant deformation (cold heading, stamping), which is the case for fasteners. Indeed, the deformation causes a partial modification of the austenitic structure into a martensitic structure (formation of martensite due to hardening) and thus becoming a little magnetic.

Each material is characterized by its aptitude for magnetization, and this law is also applicable to stainless steels. Only vacuum is probably entirely non-magnetic.

The measure of permeability of a material placed in a magnetic field is the permeability valuemr of this material with respect to vacuum (m0). The material exhibits low permeability whenmr approaches 1.

Examples:

A2: mr ≈ 1,8

A4 : mr ≈ 1,015

A4L : mr ≈ 1,005

F1 : mr ≈ 5