How reliable is non-magnetic test for Stainless Steel?

Austenitic stainless steel is not magnetic. It has to do with the grain structure. If you heat any steel up to its austenitic phase it will lose is attraction to magnets. Other grades of stainless like martensitic and precipitation hardening stainless are attracted to magnets. They are both hardenable by heat treatment too.

Fred

Not very.

Yes. 400 series stainless is magnetic. 300 series is not.

The 300 series has a different grain structure (austenitic) which won't form magnetic domains (this is the form regular steel takes when heated above the Curie point). The 400 series has a martensite grain structure which will allow magnetic domains to form. The 400 series is also heat treatable. It is what is used for stainless knife blades.

The 400 series can be hardened, but it can't be hardened quite as much as plain carbon steel of the same carbon content because of the presence of chromium (the latter is what makes it stainless).

Gary

With one exception. Work hardened 300 series is slightly magnetic. Test a SS spring and see, or test a thin piece of sheet before and after bending.

I get that all the time about 302 stainless wire brushes. The drawing process will cause attraction to a magnet. I imagine work-hardening or other physical manipulation to the stainless will do the same. I always tell people to spark-test suspected stainless and compare the sparks to known carbon steel.

Thee is only one problem wih all these answers. They are all wrong.

300 series can be quite magnetic if work hardened. Try a magnet on SS wire rope sometime. I know of a batch of 304 SS that could not be demagnitized despite the supplier's efforts. The supplier was Jorgenson Steel back before they chnaged their name to EJM. The general rule is that 300 series SS are not magnetic in the annealed condition. This is a general rule and the SS forgets to follow it sometimes. Lots of other metals like inconel are virtually impossible to tell from SS, with a magnet. Leigh@MarMachine

:Dan Musicant wrote: : :>I've always found that MOST stainless steel has little or no attraction :>to a magnet. How reliable is this test? :>

:>Is there quality stainless steel that IS drawn to magnets? :>

:>Why is most stainless steel not attracted to magnets? :>

:>While we're on the subject of stainless steel, what are it's general :>properties aside from not rusting due to oxidation? Is or can it be as :>hard as tool grade steels? Are there some neat links where I can find :>out about different kinds of steel? This has always been a facinating :>topic to me. :>

:>Dan :> :>

:Austenitic stainless steel is not magnetic. It has to do with the grain :structure. If you heat :any steel up to its austenitic phase it will lose is attraction to :magnets. Other grades of :stainless like martensitic and precipitation hardening stainless are :attracted to magnets. :They are both hardenable by heat treatment too. : :Fred

I assume, then, that when this austenitic phase steel cools below a threshhold temperature it will once again be attracted to magnets?