Naked Science Forum

Non Life Sciences => Chemistry => Topic started by: vent on 16/10/2017 10:03:37

Title: Does austenitic steel have few magnetic properties?
Post by: vent on 16/10/2017 10:03:37

I was wondering what the difference between austenitic steel and ferritic steel is and apparently their main difference is their cubic crytsal structure. Austenitic steel has a face-centered structure (SRC: https://bortec.de/en/blog/2017/08/08/austenitic-steel/) whereas ferritic steel is said to have a body-centered crystal structure. Now, I understand how these look but what I do not understand is how they behave differently and why. Why is it that austenitic steel has little to no magnetic properties due to its elemental structure for example??

Title: Re: Does austenitic steel have few magnetic properties?
Post by: chiralSPO on 16/10/2017 14:11:17

For the most part, the magnetic properties of a material have to do with how many unpaired electrons it has (there are other factors involved, but most of these can't be varied when keeping the element (Fe in this case) the same). By changing the geometry of the crystal structure, the energy levels in the metal change, and the electrons reshuffle, resulting in more or fewer unpaired electrons.

I would have to do some reading about this particular case before claiming I had the answer 100%, but I am fairly confident that this is the general case of what's going on.

Title: Re: Does austenitic steel have few magnetic properties?
Post by: evan_au on 16/10/2017 18:30:54

I understand that part of the difference is how fast it is cooled.
- If the carbon/iron alloy is cooled slowly, the carbon diffuses out of solution, so you have two intermixed compounds, one of which is iron (ferrite). The pure iron component is ferromagnetic.
- If the carbon/iron alloy is cooled rapidly, the carbon atoms are trapped in the crystal structure, distorting it, forming martensite steel.
See: https://en.wikipedia.org/wiki/Alloy#Heat-treatable_alloys

Title: Re: Does austenitic steel have few magnetic properties?
Post by: vent on 20/10/2017 12:06:42

I can't say I've completely understood ^^' But you're sure it has something to do with electrons?

Martensite Steel? What about ferritic martensitic steels then?

Title: Re: Does austenitic steel have few magnetic properties?
Post by: chiralSPO on 20/10/2017 17:47:16

Quote from: vent on 20/10/2017 12:06:42

I can't say I've completely understood ^^' But you're sure it has something to do with electrons?

Martensite Steel? What about ferritic martensitic steels then?

Yes, I am sure it has to do with the electrons. But I am not sure of the precise mechanism.
It gets awfully complicated awfully quickly, but you might be interested in looking up more info about magnetic materials.
wikipedia is often a good place to start:
https://en.wikipedia.org/wiki/Ferromagnetism
https://en.wikipedia.org/wiki/Ferrimagnetism
https://en.wikipedia.org/wiki/Paramagnetism