All Stainless Steels are attracted to a magnet with the exception of the austenitic grades i.e. 300 series. Type 303, 304, 310 and 316 are the most common grades and in their annealed condition they won’t show any response to a magnet. Nine chances out of ten if you had a grill that was punched out of SS it would be type 303 or more likely type 304. That said, cold working, machine polishing and welding can cause the grain structure in 303 or 304 to change enough to become responsive to a magnetic but stress relieving will return it to it’s non-magnetic condition. Generally speaking if you increase the nickel to chrome ratios it will remain less responsive to cold working. There for type 310 and 316 can be worked quite heavily and still remain non-magnetic.
If you look at welds that have been made on SS and that have been in service for a period of time you can notice a band a short distance from the weld that will begin to rust and has become slightly magnetic. This is because some areas of the metal adjacent to the weld cools down thru the transition temperature very rapidly causing martinsite to form. When carbides form in the lattice the austenitic grain structure changes to martinsite and it looses some of the properties that SS is known for.
Even though the 300 series SS may have become magnetic from cold working it will still not be as strongly attracted to a magnet, as would ordinary carbon steel.
Denny Graham
Sandwich, IL
