Question

How does nickel make stainless steel not magnetic?.

Answer 1

The nickel, itself ferromagnetic, reduces the magnetism in stainless steel but not to zero. Austenitic stainless steel is defined as the steel crystal structure that is face centered cubic which is the same structure hot iron has as one of the allotropes of iron. Nickel above a certain percentage (18) stabilizes austenite structure just as if you took carbon steel and heated it above 730–770 C. Above this temperature the structure is FCC and above the Currie temperature where magnetism is killed due to the isotopic symmetry of the structure. However, you can still get a small magnetic attraction from austenitic stainless steel if it is cold worked, heat treated a certain way or welded. So it is not a guarantee that austenitic stainless is totally non magnetic.