Method to determine whether stainless steel is magnetic

Update: 20-03-2020

The term stainless steel encompasses a variety of steel […]

The term stainless steel encompasses a variety of steels with completely different properties, microstructures and compositions. Stainless steel can be divided into:

Austenitic stainless steel (such as the well-known AISI 316 or 18-10): steel with FCC structure (commonly referred to as γ-iron). Most are non-magnetic. It may become weakly ferromagnetic when severely deformed.
Ferritic stainless steel: BCC or delta-iron structure, ferromagnetic (AISI 430 is the most common alloy in this class)
Duplex or duplex stainless steel: a mixture of austenite and ferrite, slightly ferromagnetic.
Precipitation hardening stainless steel: its maximum mechanical properties come from the precipitation of the second phase, they can be austenitic (17-10 PH) non-magnetic, semi-austenitic (17-7 PH) weakly magnetic or martensite (17-4 PH) Magnetic.
Martensitic stainless steel: tetragonal center structure (deformed BCC), ferromagnetic (AISI 410 is the most famous example).
Different types can be obtained by changing the composition and heat treatment. Separating magnetism from ferromagnetism is relatively simple. Take a piece of permanent magnet and bring it close to the material, if it is adhered, it is ferromagnetic, otherwise it is non-magnetic. People who process steel often use this technique rather than appreciate austenitic steel because this feature prevents them from using magnetic fixtures to hold the workpiece in positions such as grinding.