Is good grade stainless steel is no magnetism?
The answer is "It's Not True"
The magnet test is NOT a correct way to verify stainless steel.
Stainless steels are iron-based alloys primarily known for their generally excellent corrosion resistance, which is largely due to the steel's chromium concentration. Due to this difference, ferritic stainless steels are generally magnetic while austenitic stainless steels usually are not.
304 and 316 are often called austenitic grades, and 409 and 430 are called ferritic grades.
Common non-magnetic stainless steels have more chromium and molybdenum which better corrosion resistance than the common magnetic grades.
For the technically minded, in the non-magnetic grades the atoms are lined up in a crystal structure known as austenite. In the common magnetic grades the atoms are lined up in a crystal structure known as ferrite – just like in carbon steel.
☆★ It’s not even true that the “non-magnetic” grades are never magnetic. As supplied, sheet and coil are non-magnetic, but when they are worked (Forged, Welded, bent) they become magnetic.
The strength of the magnetism depends on how much the metal has been deformed. Even when these grades are cut (cold, by shearing) the deformation in the edge of the metal causes magnetism. ☆★
Video summaryAustenitic Stainless Steels normally not Magnetic, but they can become Magnetic if they have been deformed or had been Cold worked in the past. In this video I demonstrate the fact that Austenitic Stainless Steel can become Magnetic. This exhaust muffler Tip is made from Austenitic Stainless Steel and therefore it is not magnetic, but there are some areas on the steel that had been deformed (round corners / fillets) and these areas are truly magnetic.