Stailess steel question for Mete or anyone else.

M

miden

Joined
Sep 9, 2005
Messages
835
Hi Guys,
I was wondering what it is that makes some stainless steels magnetic and others not.
Before I go wading through the WWW I was thinking maybe someone could help and there may be others on the Forum who would also be interested to know.;)
Thanks,

Mike
 
Remember the three basic crystal structures of steel , ferrite, martensite ,and austenite .Ferrite and martensite are magnetic, austenite is not.When we heat carbon steels starting out with ferrite which is magnetic but becomes non-magnetic when it changes to austenite . The alloy content of some of the stainless steels makes them austenitic at room temperature therefore non-magnetic as in the 300 series austenitic stainless steels....There are some generalizations here but we won't go into the complex physics of magnetism.
 
The non magnetic stainless steels are austinitic (as opposed to ferritic or martinsitic), which basically means that the form of the crystals in the steel are the same as normal steel gets at around 1450F when it hits critical temp and becomes non-magnetic. The transformation point for austinitic steels are below room temperature, so if you got them cold enough they'd become magnetic. Also work hardening can transform some of the austinite even at room temp and it can become mildly magnetic. Someone with more understanding then me will have to tell you why the transformation temp is below room temp, that part is a little over my head.

edit: Mete snuck in there while I was typing.
 
Thanks Mete and AwP.
I understand about the structure of the crystals. However, do the elements that the steel is composed of have anything to do with the magnetism?

Also, I understand this is a very complex subject, almost as complicated as a woman:eek:
I was not expecting "give me 5 minutes of your time and teach me all you know";)
As you know. the www can be a great source of info but sometimes it is difficult to nail a subject down precisely, can any of you point me in the direction of a good link that will make me a bit wiser?

Thanks,

Mike
 
There are the temperatures MS and Mf ,the start and finish of the martensite transformation .There is also the Md temperature which is above the Ms temperature and this is the temperature where there is transformation to martensite due to deformation !So a 304 stainless cable which has been cold drawn may be partially magnetic !!.....The question of magnetism has come up on another forum and researching it is challenging .It is physics.For example as we heat steel above the critical it doesn't immediately become nonmagnetic . The Curie temperature is about 1414F, above the critical.Then of course one has to ask how there is a transformation to delta ferrite at about 2600F and a return to magnetic !! While we think of iron, nickel,cobalt as ferromagnetic they've created weird ferromagnetic compounds containing none of these elements ! It's all a mystery to me.
 
Miden - mete and AwP already explained the austentitic steel.The answer to your question about the elements in the steel affecting the magnetic properties is yes.It is the iron in the steel that makes it magnetic.it is the crystal structure that may make it non-magnetic.and it is the elements in the alloy that can affect the point at which this happens.
Or maybe it is just magic.
Another example of this is dendritic cobalt (cast stelite 6B).Cobalt is magnetic,dendritic cobalt is not.
Stacy
 
Mete, if it is a mystery to you then how do you think it makes a toolmaker like me feel?
You, AwP and Fitzo had me feeling a lot better earlier on.:D
Now I am rattled again. Thanks buddy.

Seriously though, physics is an amazing thing.
Being in the trade that I am I like to know WHY things are the way that they are, that way you can better deal with the challenges and problems that crop up.
Knife making in itself is such a science and as I said in an earlier post, it is good to inform yourself as much as possible because one day that may be the difference between making a sale or not or strengthening ones reputation, or not. Besides all that, I just like to know what I am dealing with.

I always thought an alloy had to have a significant amount of iron in it to make it magnetic and that other elements in large quantities could render it non-magnetic......mumble, mumble.......

When you see what a big impact the tiniest amounts of certain elements can have on a steel you can but shake your head in wonder.
Wondering is something I do a lot of.......

Take care All, and thanks for the input.:thumbup:

Good to see there are others as confused as me.:eek:

Mike
 
Its been awhile since I took any classes on this sort of stuff, so I'm sort of pulling at straws here.

I do remember that magnetism is also related to electron spin. If the electrons of the different atoms are lined up correctly in their travel, you have a magnetic attraction.
Electrons travel in different orbitals depending on how many the atom has (which depends on which element you're talking about) and what energy level the electron is at.
Heat is a form of energy, so by changing the temperature of the material you are effecting the energy level, which would effect the electrons.
Because there are very few materials that can be magnetic, I suppose its a decent bet that there is a very limited set of conditions that have to be right in terms of how many electrons and how they are aligned, to have magnetism. So it would seem to follow that by making changes to their travel, by changing their energy level (which would make them move up into a different orbital) you could move the electrons out of that narrow range of conditions necessary for magnetism.
 
Matt, That is a common misconception about the energy level of the electrons and their magnetic alignment.If heating them up would make them non magnetic,then delta iron would not be magnetic (2600 degrees).It is the way the electrons can flow from one atom to the other,which is governed by the crystal structure,that allows the material to be magnetic or not.
Magnetism is not rocket science,but it is quantum physics.
 
Here's a pretty good technerd explanation for magnetism. I love the quantum mechanical mysticism of trying to convert the mathematics to a language-based description. Sorta "certain atoms like to hang out together and when they do, they start carrying on the same." Cool.

http://www.mathpages.com/home/kmath240/kmath240.htm
 
bladsmth said:
Matt, That is a common misconception about the energy level of the electrons and their magnetic alignment.If heating them up would make them non magnetic,then delta iron would not be magnetic (2600 degrees).It is the way the electrons can flow from one atom to the other,which is governed by the crystal structure,that allows the material to be magnetic or not.
Magnetism is not rocket science,but it is quantum physics.
Click to expand...

I wasn't trying to say that it was so much temperature specific, as much as it was about overall change. Maybe you change one level and you are no longer magnetic, add enough energy and you push things back into the right alignment to become magnetic again.
I suppose that could still be way off, like I said its been awhile since I took qauntum physics and chemistry and all that :D
I do understand about the crystal structure. Austenite being a solid solution of carbon in FCC (gamma) iron, which is the non magnetic structure for iron, and ferrite being a solid solution of carbon in BCC iron, which is magnetic.
Adding alloy content like nickel can stabilize the austenite at room temperature, which is what gives you things like the 300 series stainless steels which are non magnetic.
The different crystal structures are based on different alignment of atoms. Face centered cubic, and body centered cubic. I just thought maybe you could tie energy levels and orbitals into that somehow. Maybe not:confused: :D
 
Matt, I am leaning toward the magic explanation.
All this reminds me of my physics days.
When I was younger (and crazier) I used to build all sorts of high energy gizmos (Tesla coils,Van de Graffs,etc.).I still have a 50KV Jacobs ladder in the garage.The neatest was a flame speaker.I fed hydrogen into a Bunsen burner an had platinum electrodes sticking into each side of the flame envelope.A high voltage was created with a HV transformer and modulated with an audio transformer.The sound came out of the flame (It has to do with plasma,ions, and magic fairies). It was eerie to listen to the flame sing.I would feed it the Arthur Brown song "I am the God of Hellfire..."
Not that you guys had any doubt,but now you know how strange I am.
Stacy
 
bladsmth said:
When I was younger (and crazier) I used to build all sorts of high energy gizmos (Tesla coils,Van de Graffs,etc.).I still have a 50KV Jacobs ladder in the garage.The neatest was a flame speaker.I fed hydrogen into a Bunsen burner an had platinum electrodes sticking into each side of the flame envelope.A high voltage was created with a HV transformer and modulated with an audio transformer.The sound came out of the flame (It has to do with plasma,ions, and magic fairies). It was eerie to listen to the flame sing.I would feed it the Arthur Brown song "I am the God of Hellfire..."
Not that you guys had any doubt,but now you know how strange I am.
Stacy
Click to expand...
I wonder if you could have done that to Jackson's hair when it caught on fire
I wonder what color he'd be now:eek: toast :)

Stacy , bring it out again. you could make a lot of money on TV scaring the bajeeba's out of the kids on those iditot shows they have now..:)
 
bladsmth said:
Matt, I am leaning toward the magic explanation.
All this reminds me of my physics days.
When I was younger (and crazier) I used to build all sorts of high energy gizmos (Tesla coils,Van de Graffs,etc.).I still have a 50KV Jacobs ladder in the garage.The neatest was a flame speaker.I fed hydrogen into a Bunsen burner an had platinum electrodes sticking into each side of the flame envelope.A high voltage was created with a HV transformer and modulated with an audio transformer.The sound came out of the flame (It has to do with plasma,ions, and magic fairies). It was eerie to listen to the flame sing.I would feed it the Arthur Brown song "I am the God of Hellfire..."
Not that you guys had any doubt,but now you know how strange I am.
Stacy
Click to expand...

Your best pal in those days was Timothy Leary, right? :cool: You and him used to jam with David Crosby, Jimi Hendrix, and Jim Morrison. Of course, Hunter S. Thompson was there to record the whole event. :D
 
miden said:
what was Elvis doing while all this was going on?:D

Mike
Click to expand...

About that time he was chowin' down a couple 'Ludes and washing it down with a box of HoHo's while he hung out in the world's flashiest bass-fishing jumper ever! :D
 
LOL....and then Sachmo and Bing did a rendition of "Gone Fishin'....

I never quite realized the magnitude of this thread when I started it.....:D :D

It seems there is a lot more than knifemaking knowledge availabe here, I LIKE IT!

Thanks Guys, for everything.:thumbup:

Mike
 
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