Magnetic weapons

Jens Nordlunde · 26th February 2005, 10:42 AM

Gene, thank you for answering my questions – also the questions not asked. There is however one question which I did not ask, and which you did not answer. The iron powder you use, how fine is it, is it like table salt, or not quite as fine? From your pictures I think it must be rather fine, but I am not sure.
To my opinion you should go on with the experiment, as I find it interesting and have learned quite a lot from the different answers. Another reason is, that I can’t remember to have seen an experiment like this one on this forum before, although this is/should be part of the interest when collecting swords and daggers.
Jens

Ann Feuerbach · 27th February 2005, 05:14 PM

Hello all!
Now that I have replaced my painfully slow old computer I can start to join in. At the risk of being slightly off the track, here are some thoughts/comments etc on magnetism of crucible Damascus steel blades, for what it is worth.... It would not matter if magnetite was part of the smelt or crucible steel refining process. During the actual production of the crucible steel, since it is liquid and an homogenous steel, the iron particles in the ingot would have a definite alignment to magnetic north (back to Archaeomagnetism). If anyone is really interested in that I could probably give some references as I was teaching it a few weeks ago.
I have heard from those producing crucible Damascus steel today, that at least one blacksmith repeatedly tests the bade during forging, to know when the pattern is good. I will try to find that e-mail, in a list of 500, so it may take a while. Plus, polishing with a loadstone may effect the magnetic properties.
As soon as I get a chance (not till the summer) I will research this topic further, looking for historical references and I will suggest some scientific explinations.
I thought I have covered all aspects of crucible Damascus steel, but magnetivity and sound are the two new brain teasers!

Ann
http://moltenmuse.home.att.net
http://www.AASTI.us

Jens Nordlunde · 27th February 2005, 05:31 PM

Hello Ann, and welcome to the forum.
Do you know, are any of the ingots from the different parts of India magnetic?
In the book ‘The Mansabdari System and the Mughul Army’ the author, Abdul Aziz place the lodestone/Magnetite amongst the semi precious stones. What does it look like?
The sound is interesting. When you can make a katars side guards sound like a tuning fork for a looong time, it is fantastic, but when you try with a katar where the hilt has been cast, the sound is very short.

Jens

Andrew · 27th February 2005, 05:31 PM

Welcome to the forum, Dr. Feuerbach.

Rivkin · 27th February 2005, 06:06 PM

Quote:

Originally Posted by Ann Feuerbach

It would not matter if magnetite was part of the smelt or crucible steel refining process. During the actual production of the crucible steel, since it is liquid and an homogenous steel, the iron particles in the ingot would have a definite alignment to magnetic north (back to Archaeomagnetism). If anyone is really interested in that I could probably give some references as I was teaching it a few weeks ago.

I'm sorry, may be I'm not getting something but:
I understand that magnetite will not make a difference, but taking in mind that iron melts at 1800K, and its Curie temperature is 1000K how it can have (in a liquid state) _any_ definite magnetization. If at 1000K the exchange can not hold these guys together, thermal energy should completely negate any infinitesmal influence that the Earth's magnetic field can possibly have on a liquid metall. Most of steels have Curie temperatures even lower than this, up to 300K and below for some non-corrosive nickel and other steels.

What do you mean by "iron particles" in the _liquid_ ? Domains ? Individual spins ? Non-uniformities of a liquid state ?

Ann Feuerbach · 27th February 2005, 07:52 PM

Perhaps the ingot does not have a magnetic alignment.

I do not know of any experiments done on the archaeomagnetism of iron objects because for archaeomagnetism to be studies, the object must be in situ since firing. Archaeomagnetism is based on the principle of Thermoremanent magnetism (TRM). When a material containing iron such as clay, is heated to above 700 C (1290 F) the iron particles in the clay align to face magnetic north. The direction and intensity of the magnetism of the kiln or hearth is measured to give the date. I assumed that the same principle would have applied to the crucible steel. All the literature I have read just refers to "iron particles". Perhaps I am wrong and the ingot would not have had a TRM. As I said, I must do some more research on this. I must point out that having TRM and being magnetic are different things. As a side not, I have noticed that many archaeological slags with high iron content and iron lumps, that one side is definitly attracted to a magnete while the other side definitly repels.
Ann

Rivkin · 27th February 2005, 09:34 PM

Neither ignot nor iron objects nor any objects would have any magnetization when heated above Curie temperature.

What TRM is, is when cooled _slowly_ the object that in general is macroscopically isotropic will be magnetized along the Earth's magnetic field (with some exceptions).
I think that magma is Fe3O4 or something like this, and it can move around without loosing its magnetization, so the TRM happens when it's actually very hot, but I'm not quite sure about it.Very primitive discussion is located here:
http://www.moorlandschool.co.uk/earth/magnetism.htm

Rivkin · 27th February 2005, 10:13 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.

Ann Feuerbach · 27th February 2005, 11:18 PM

Thanks. Lots of food for thought!

26th February 2005, 10:42 AM	#1
Jens Nordlunde Member Join Date: Dec 2004 Location: Europe Posts: 2,718	Gene, thank you for answering my questions – also the questions not asked. There is however one question which I did not ask, and which you did not answer. The iron powder you use, how fine is it, is it like table salt, or not quite as fine? From your pictures I think it must be rather fine, but I am not sure. To my opinion you should go on with the experiment, as I find it interesting and have learned quite a lot from the different answers. Another reason is, that I can’t remember to have seen an experiment like this one on this forum before, although this is/should be part of the interest when collecting swords and daggers. Jens

27th February 2005, 05:14 PM	#2
Ann Feuerbach Member Join Date: Feb 2005 Posts: 133	Hello all! Now that I have replaced my painfully slow old computer I can start to join in. At the risk of being slightly off the track, here are some thoughts/comments etc on magnetism of crucible Damascus steel blades, for what it is worth.... It would not matter if magnetite was part of the smelt or crucible steel refining process. During the actual production of the crucible steel, since it is liquid and an homogenous steel, the iron particles in the ingot would have a definite alignment to magnetic north (back to Archaeomagnetism). If anyone is really interested in that I could probably give some references as I was teaching it a few weeks ago. I have heard from those producing crucible Damascus steel today, that at least one blacksmith repeatedly tests the bade during forging, to know when the pattern is good. I will try to find that e-mail, in a list of 500, so it may take a while. Plus, polishing with a loadstone may effect the magnetic properties. As soon as I get a chance (not till the summer) I will research this topic further, looking for historical references and I will suggest some scientific explinations. I thought I have covered all aspects of crucible Damascus steel, but magnetivity and sound are the two new brain teasers! Ann http://moltenmuse.home.att.net http://www.AASTI.us

27th February 2005, 05:31 PM	#3
Jens Nordlunde Member Join Date: Dec 2004 Location: Europe Posts: 2,718	Hello Ann, and welcome to the forum. Do you know, are any of the ingots from the different parts of India magnetic? In the book ‘The Mansabdari System and the Mughul Army’ the author, Abdul Aziz place the lodestone/Magnetite amongst the semi precious stones. What does it look like? The sound is interesting. When you can make a katars side guards sound like a tuning fork for a looong time, it is fantastic, but when you try with a katar where the hilt has been cast, the sound is very short. Jens

27th February 2005, 05:31 PM	#4
Andrew Member Join Date: Nov 2004 Location: USA Posts: 1,725	Welcome to the forum, Dr. Feuerbach.

27th February 2005, 07:52 PM	#6
Ann Feuerbach Member Join Date: Feb 2005 Posts: 133	Perhaps the ingot does not have a magnetic alignment. I do not know of any experiments done on the archaeomagnetism of iron objects because for archaeomagnetism to be studies, the object must be in situ since firing. Archaeomagnetism is based on the principle of Thermoremanent magnetism (TRM). When a material containing iron such as clay, is heated to above 700 C (1290 F) the iron particles in the clay align to face magnetic north. The direction and intensity of the magnetism of the kiln or hearth is measured to give the date. I assumed that the same principle would have applied to the crucible steel. All the literature I have read just refers to "iron particles". Perhaps I am wrong and the ingot would not have had a TRM. As I said, I must do some more research on this. I must point out that having TRM and being magnetic are different things. As a side not, I have noticed that many archaeological slags with high iron content and iron lumps, that one side is definitly attracted to a magnete while the other side definitly repels. Ann

27th February 2005, 09:34 PM	#7
Rivkin Member Join Date: Dec 2004 Posts: 655	Neither ignot nor iron objects nor any objects would have any magnetization when heated above Curie temperature. What TRM is, is when cooled _slowly_ the object that in general is macroscopically isotropic will be magnetized along the Earth's magnetic field (with some exceptions). I think that magma is Fe3O4 or something like this, and it can move around without loosing its magnetization, so the TRM happens when it's actually very hot, but I'm not quite sure about it.Very primitive discussion is located here: http://www.moorlandschool.co.uk/earth/magnetism.htm

27th February 2005, 10:13 PM	#8
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.

27th February 2005, 11:18 PM	#9
Ann Feuerbach Member Join Date: Feb 2005 Posts: 133	Thanks. Lots of food for thought!