Ethnographic Arms & Armour - View Single Post

Rivkin · 27th February 2005, 09:13 PM

Again - magnetic properties of a macroscopic iron is a tremendously complex problem, that can be approach with numerics.

I'm not a specialist (so I wish to be corrected by ones), but:

Local magnetic structure depends on the crystalline lattice (unobtainable in normal conditions "diamond" iron for example is even anti-ferromagnetic), including stress, grain size etc. There are dozens (!) of phases that correspond to basically chemically similar steels that have different crystalline structure (and btw hardening is the way to obtain a metastable crystalline structure).
These lectures notes can be of help:
http://neon.mems.cmu.edu/laughlin/pdf/252.pdf
btw austenite is paramagnetic.
It will greatly depends on local chemical decomposition.
It's going to greatly depend on how uniform and fast the cooling is (uniform cooling leads to permanent magnetization alongside the local magnetic fields)
In general there are some companies who measure conductivity and magnetic permeability in order to undestand how uniform their steel is. I don't want to refer to non-publicly available papers, so:
http://doc.tms.org/ezMerchant/prodtm...df?OpenElement

Now to the question "what happens to a sword":
1. Swords are intrinsicly anisotropic due to their shape.
2. They are usually completely non-uniform in their magnetic properties due to nonuniformities of steel they are made off, and nonuniform cooling (first of all - nonuniform quenching).

Before I've the patterns of the dagger that were shown here I believed that such patterns can be produced by a weird external field. Now I think that because they are so damn non-uniform, and most of the dagger is not magnetized at all, the structure of this dagger should be tremendously non-uniform by itself, and I believe that conductance or X-Ray tests can prove that.

Now to what happens to swords when they lie in Earth. I thought about who would've been interested in this, and realzied that mine detector peoples are.
And indeed one can read a very interesting pamphlet over here:
http://neon.mems.cmu.edu/laughlin/pdf/252.pdf]

one should keep in mind that they are interested in a dipole moment i.e. the magnetic field procuded by objects very far away from the object itself, so it's much more uniform and depends on Earth's magnetic field in a much more direct way (since those guys quetly cool down underground), but we are interested in a local magnetization - quadrupole and up moments, that create these beautiful patterns.

27th February 2005, 09:13 PM	#66
Rivkin Member Join Date: Dec 2004 Posts: 655	Again - magnetic properties of a macroscopic iron is a tremendously complex problem, that can be approach with numerics. I'm not a specialist (so I wish to be corrected by ones), but: Local magnetic structure depends on the crystalline lattice (unobtainable in normal conditions "diamond" iron for example is even anti-ferromagnetic), including stress, grain size etc. There are dozens (!) of phases that correspond to basically chemically similar steels that have different crystalline structure (and btw hardening is the way to obtain a metastable crystalline structure). These lectures notes can be of help: http://neon.mems.cmu.edu/laughlin/pdf/252.pdf btw austenite is paramagnetic. It will greatly depends on local chemical decomposition. It's going to greatly depend on how uniform and fast the cooling is (uniform cooling leads to permanent magnetization alongside the local magnetic fields) In general there are some companies who measure conductivity and magnetic permeability in order to undestand how uniform their steel is. I don't want to refer to non-publicly available papers, so: http://doc.tms.org/ezMerchant/prodtm...df?OpenElement Now to the question "what happens to a sword": 1. Swords are intrinsicly anisotropic due to their shape. 2. They are usually completely non-uniform in their magnetic properties due to nonuniformities of steel they are made off, and nonuniform cooling (first of all - nonuniform quenching). Before I've the patterns of the dagger that were shown here I believed that such patterns can be produced by a weird external field. Now I think that because they are so damn non-uniform, and most of the dagger is not magnetized at all, the structure of this dagger should be tremendously non-uniform by itself, and I believe that conductance or X-Ray tests can prove that. Now to what happens to swords when they lie in Earth. I thought about who would've been interested in this, and realzied that mine detector peoples are. And indeed one can read a very interesting pamphlet over here: http://neon.mems.cmu.edu/laughlin/pdf/252.pdf] one should keep in mind that they are interested in a dipole moment i.e. the magnetic field procuded by objects very far away from the object itself, so it's much more uniform and depends on Earth's magnetic field in a much more direct way (since those guys quetly cool down underground), but we are interested in a local magnetization - quadrupole and up moments, that create these beautiful patterns.