Can Stainless Steel Be Magnetic?

[cragar]

Is stainless steel magnetic?

 

[Physics_Kid]

some stainless steels are magnetic. so some seaching for the types/classifications of stainless steels.

 

[mgb_phys]

Generally the higher the nickel content the less magnetic.
All stainless steels will effect a compass but austenitic (300 series) won't stick to a magnet.

 

[nucleus]

Yes and No!
http://www.azom.com/Details.asp?ArticleID=1140#_Austenitic_Grades
http://www.google.com/support/websearch/bin/answer.py?hl=en&answer=134479

 

[Bob S]

The 400 series stainless steel (martinsetic, e.g., 440C stainless) is generally magnetic, while the 300 series (austinetic, e.g., 304 and 316) is not.

 

[Physics_Kid]

i think i jumped the gun with my answer. considering this is a physics forum i think my reply should have been something like this:

yes, all materials are "magnetic", they all have atoms which have electric and magnetic fields as properties. the question is too general.

if you (the OP) is asking if you can have a magnet stick to stainless then for some stainless steels you need a very strong magnet while for other types of stainless a weak magnet will stick to it.

 

[vanesch]

Iron has two crystal structures, ferrite which is magnetic and austenite which is not (it is paramagnetic, not ferromagnetic). So if your steel contains enough ferrite, it will be (ferro-)magnetic, if not, it won't. Note that martensite is "metastable" austenite, but with a deformation of the crystal structure, and apparently, it is also ferromagnetic.

 

[cragar]

yes, all materials are "magnetic"

Do you consider photons to be a material , do photons have a magnetic moment?

ok so i see there is no cut an dry answer to my question .

 

[vanesch]

Do you consider photons to be a material , do photons have a magnetic moment?

ok so i see there is no cut an dry answer to my question .

I took it that you meant "ferromagnetic". And then it depends on the composition of the stainless steel.

 

[cragar]

what do you mean by ferro magnetic

 

[botagar]

if i remember right from high school physics, Ferro Magnetic means that it is easily magnetized. the domains in the metal align according to the magnet therefore becomming magnetic *i think*.

Google?

 

[vanesch]

what do you mean by ferro magnetic

Probably what you mean by "magnetic". "is attracted by a magnet". It is only in ferromagnetic materials that this phenomenon is strong enough to be easily noticed. Many materials have some form of magnetism, which goes under the names of diamagnetism and paramagnetism, but these are small effects compared to ferromagnetism. You need sensitive lab tools to observe it.

 

[cragar]

does ferro mean conating iron , you pretty much i mean will a magnet stick to it
my chem teacher told me that iron ,cobalt, nickel and liquid oxygen would be affected by a magnet.

 

[Physics_Kid]

Do you consider photons to be a material , do photons have a magnetic moment?

ok so i see there is no cut an dry answer to my question .

strong magnetic field will bend light.

all matter is subject to interaction with magnetic fields. the amount of interaction depends on type of material and flux of magnetic field.

 

[cragar]

is the magnetic field bending the light or the gavitational field made by the magnetic field bending the light.

 

[vanesch]

strong magnetic field will bend light.

?

In classical electromagnetism, no. In QED, there are extremely small corrections which would make for photon-photon interactions, but they will not be such that light is bent, but rather scattered.

Extremely strong magnetic fields will however generate, in general relativity, some curvature (generate some gravity) and that may bend light theoretically. But we are talking about extremely tiny effects here, which, I would guess, are not open to experimental inquiry, as they are so terribly small.

 

[mgb_phys]

is the magnetic field bending the light or the gavitational field made by the magnetic field bending the light.

A magnetic field doesn't bend light (there is a quantum effect where photons can convert into electron/positron pairs that are effected by a magnetic field)
A magnetic field doesn't create a gravitational field - other than the mass of the magnet of course!

 

[Physics_Kid]

i am reaching outside of my immediate knowledge base. a magnetic field can create a gravitational lensing which would cause light to bend.

be it the gravity field by which light bends, the cause was a magnetic field.

 

[Phrak]

http://en.wikipedia.org/wiki/Electromagnetic_stress-energy_tensor"

 

[cragar]

A magnetic field doesn't create a gravitational field

The associated particle with the magnetic field is the photon right ?
so a magnetic field creates no gravity at all ,
do photons create gravity.
are magnetic fields affected by gravity.

 

[vanesch]

The associated particle with the magnetic field is the photon right ?
so a magnetic field creates no gravity at all ,
do photons create gravity.
are magnetic fields affected by gravity.

A magnetic field does create a gravitational field according to general relativity, but such a tiny one that it will for all practical purposes remain undetectable.

The reason is that the energy density of the magnetic field acts as a source for gravity. But the energy density of a magnetic field is way way less dense than any piece of matter (unless the fields become mind bogglingly strong, at which point other things will happen) so it will generate something like a gravity field of a laboratory vacuum or something (I'm guessing here, could be orders of magnitude wrong).

 

[vanesch]

According to the book that I’ve read stainless steel are very broad group of metals. The advantage of stainless steels over plated steels is that, if scratched or damaged, the steel will ‘self-repair’ as new oxide layer is formed. In general, the higher the proportion of chromium, the stronger the corrosion resistance of the steel. as for whether they are magnetic, the answer is that it depends. There are 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 ‘austentic’ – these have higher chromium content an dnickel is also added. It is the nickel which modifies the physical structure of the steel and makes it non-magnetic.

Actually, it is the crystal structure of the iron that makes it magnetic or non-magnetic (ferro, that is). Ferrite (alpha-iron) is body-centered cubic and is magnetic ; austenite (gamma-iron) is face-centered cubic and is non-magnetic. Now, pure iron is thermodynamically stable at room temp in the alpha phase, and is thermodynamically stable in the gamma phase around 1000 C or something. But we can make room-temp steels in the gamma-phase, in two ways:
- they are not thermodynamically stable but "frozen in",
- their thermodynamical stability has changed because of alloy elements like nickel and chrome and so.

The "freezing in" comes about by fast cooling. Depending on the speed of cooling, you can get a martensitic structure, which is an alpha-like (body-centered) structure, but which is deformed (it is not cubic) because of the presence of carbon which didn't get enough time to diffuse out. Martensite is not thermodynamically stable. I don't know if it is ferromagnetic or not, in fact. I would guess so (as it is BCC-like).

Stainless steel usually consists of gamma-phase iron, so is mainly non-magnetic. It can contain parts of ferrite (alpha) so it can be slightly ferro-magnetic. The presence of nickel and chrome can also alter the magnetic properties.

So this means that the ferro-magnetic properties of steel are very dependent on exactly what material structure it has (ie, on the precise metallurgic kind of steel).

 

[Bob S]

Actually, it is the crystal structure of the iron that makes it magnetic or non-magnetic (ferro, that is). Ferrite (alpha-iron) is body-centered cubic (bcc) and is magnetic ; austenite (gamma-iron) is face-centered cubic (fcc) and is non-magnetic. .

I used austenetic stainless (SS304, as I recall) in a piece of equipment that was cooled to about 4 kelvin. Somewhere between room temperature and 4 kelvin, it switched from fcc to bcc, and in the process became magnetic, and in addition the dimensional change from fcc to bcc was sufficient to crush a ceramic insert (vacuum seal) that was hard-soldered to the SS304.

Bob S

 

[vanesch]

I used austenetic stainless (SS304, as I recall) in a piece of equipment that was cooled to about 4 kelvin. Somewhere between room temperature and 4 kelvin, it switched from fcc to bcc, and in the process became magnetic, and in addition the dimensional change from fcc to bcc was sufficient to crush a ceramic insert (vacuum seal) that was hard-soldered to the SS304.

Bob S

Wow, fun

I suppose this came about because of too large a "thermodynamic stress" (the colder you get, the more the austenitic phase is out of equilibrium). On the other hand, one would also guess that the colder, the slower all kinetics, so I didn't know it was possible to have such a phase transition at low temperatures.

 

[MagnetDave]

I used austenetic stainless (SS304, as I recall) in a piece of equipment that was cooled to about 4 kelvin. Somewhere between room temperature and 4 kelvin, it switched from fcc to bcc, and in the process became magnetic, and in addition the dimensional change from fcc to bcc was sufficient to crush a ceramic insert (vacuum seal) that was hard-soldered to the SS304.

Bob S

Are you sure that it was the cold? I've seen it before in cryo systems that the strain from the forming process caused the phase transition, but I've never heard of it happening from cold alone. It's very interesting if that's the case, and I'd like to talk in about it in more detail.

 

[Bob S]

Are you sure that it was the cold? I've seen it before in cryo systems that the strain from the forming process caused the phase transition, but I've never heard of it happening from cold alone. It's very interesting if that's the case, and I'd like to talk in about it in more detail.

Yes, I am sure. It happened many times while cooling superconducting magnets to 4.2 kelvin, until I switched from SS316 to a coaxial connector with a ceramic dielectric using a cupro-nickel alloy.

Bob S

 

[MagnetDave]

Yes, I am sure. It happened many times while cooling superconducting magnets to 4.2 kelvin, until I switched from SS316 to a coaxial connector with a ceramic dielectric using a cupro-nickel alloy.

Bob S

Any idea what the transition temperature was?

 

[Bob S]

Any idea what the transition temperature was?

Above 9 kelvin.

Bob S

 

[JDługosz]

does ferro mean conating iron , you pretty much i mean will a magnet stick to it
my chem teacher told me that iron ,cobalt, nickel and liquid oxygen would be affected by a magnet.

Liquid oxygen is paramagnetic. Solid (and not too warm) iron, nickel, and cobalt are ferromagnetic. See http://en.wikipedia.org/wiki/Paramagnetism" .

 

[JDługosz]

Wow, fun

I suppose this came about because of too large a "thermodynamic stress" (the colder you get, the more the austenitic phase is out of equilibrium). On the other hand, one would also guess that the colder, the slower all kinetics, so I didn't know it was possible to have such a phase transition at low temperatures.

Some knives are treated with cryogenic temperatures to affect the nature of the steel. I read that http://en.wikipedia.org/wiki/Cryogenic_hardening" .

 

[Bob S]

The abstract of this article implies that the austenitic-to-martensitic transformation in SS316 occurs ~40 kelvin when cooling the sample.

http://jap.aip.org/resource/1/japiau/v108/i4/p043904_s1?isAuthorized=no

Does it transform back to austenitic at 40 kelvin when temperature is rising?

Bob S

 

[JDługosz]

Well, that can't be the same thing used for making blades, unless it differs with alloy, since that is a balmy 77.36 liquid nitrogen bath.