On Mon, 22 Dec 2008 14:24:15 -0600, "mcdonaldREMOVE TO ACTUALLY REACH
wrote in :

We have an employee with some of those fancy stainless steel
appliances. She says magnets don't stick.
Then it's not stainless steel.

Some grades of stainless steel aren't magnetic. Depends on how much
nickel is in it, I gather.

No, how much chromium. Low chromium makes it magnetic.

No, nickel. See
http://www.physlink.com/Education/AskExperts/ae546.cfm

Question

Is stainless steel magnetic? Does it depend on the amount of
chromium, or nickel alloy?

Asked by: James McGuigan

Answer

Stainless steels are a very broad group of metals. The name was
adopted as a generic term for steel alloys with a minimum of 10.5%
chromium. The chromium gives the steel its 'stainless' properties -
essentially corrosion resistance. On the surface of the metal, a very
thin chromium-rich oxide layer is formed which is inert - i.e. it
prevents the steel from rusting. The advantage of stainless steels
over plated steels is that, if scratched or damaged, the steel will
'self-repair' as a new oxide layer is formed. In plated steels,
scratches in the plate will often lead to corrosion of the steel
underneath.

In general, the higher the proportion of chromium, the stronger the
corrosion resistance of the steel. In addition to chromium, other
metals are added to give the steel particular properties such as
strength and malleability. Specifically nickel is used to strengthen
the oxide layer.

As for whether they are magnetic, the answer is that it depends.
There are several families of stainless steels with different
physical properties. A basic stainless steel has a 'ferritic'
structure and is magnetic. These are formed from the addition of
chromium and can be hardened through the addition of carbon (making
them 'martensitic') and are often used in cutlery. However, the most
common stainless steels are 'austenitic' - these have a higher
chromium content and nickel is also added. IT IS THE NICKEL WHICH
MODIFIES THE PHYSICAL STRUCTURE OF THE STEEL AND MAKES IT
NON-MAGNETIC. [emphasis added]

So the answer is yes, the magnetic properties of stainless steel are
very dependent on the elements added into the alloy, and specifically
the addition of nickel can change the structure from magnetic to
non-magnetic.

The following company website has a useful high-level definition of
the broad stainless steel categories.
http://www.parkrow.org/stainless_steel.htm

Answered by: Jules Seeley, M.S., Physics graduate; Strategy
Consultant, London.

--
Best regards,
John
Panasonic DMC-FZ8, DMC-FZ20, and several others