Magnetic weapons

[Jens Nordlunde]

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]

Welcome to the forum, Dr. Feuerbach.

[Rivkin]

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]

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]

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]

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]

Thanks. Lots of food for thought!

[Rivkin]

You are welcome.

Btw, the thing I always wondered about archaeomagnetism people - do you take in mind only the total magnetization and connect it to the strength of the Earth's magnetic field at the time of making of the object, or you actually use oomf/rkmag to see how the object with such chemistry and shape would react to the applied magnetic field of such strength ?

[Jim McDougall]

Hello Ann,
I would like to also welcome you to our forum, and to say what an honor it is to have you join us. I have had your outstanding work "Crucible Damascus Steel"for some time now, and it is brilliantly written!
For someone such as myself who is fascinated with history, yet lost with the complexities of physics, science and technology, it is an entirely readable and well crafted blend of history with well explained technical details.

This thread, as well as that of meteoric iron, have really become high profile and I am delighted that Jens posted them, as the knowledge and discussion has become irresistable! Aside from your extremely interesting article, most discussions on these topics can be quite dry to most of us in the lay world....but this thread keeps getting better, and your joining us is outstanding!

All the best,
Jim

[Ann Feuerbach]

Thank you Jim for your kind praise. Believe it or not, I was condemed by my PHD supervisor for not writing "academic" enough. I think that means big words and complicated sentence structures! However, my Russian friends said they like it because they can actually read/translate it easily. I always thought that the was the point of academic writing. Obviously I am not of the elitest academic type. I have so much more to add for the book that could not be put in the PhD
As to archaeomagnetism testing. I believe that the process involves carefully measuring the angle of declination as well as intensity and direction before it is removed from the ground, and then again in a special chamber to eliminate outside forces. I do not recall off hand how much the objects make up is involved.

[Mare Rosu]

OK ALL
I said I was winding down on my part of this thread started by JENS, and after reading
Ann and RIVKIN input on this magnetic stuff I should have stopped last week! Do all you follow their exchange? Man that is some heavy stuff. Anyway I said I would do as FEARN suggested and acquire a magnetic knife holder and zap a carbon blade.
I used a Case butcher knife, as was in contact with the magnetic holder for approximately five minutes, the pictures show that the blade did take magnetic profile with three pols.
I also took a picture of the Mysore dagger with four compasses on the blade to show you that it has the four changes all at the same time.
Gene

[Jim McDougall]

Hi Ann,
That is exactly what is great! You are able to discuss material that is typically pretty involved and technical and integrate fascinating historical data, which makes it possible to understand
The original course of this thread was to try to discover how extensively lodestone was involved in the wootz in blades. In some of the material we discovered it seems that it inadvertantly occurred in the raw material from Hyderabad, which remained in certain janbiyya blades found in Arabia.

The ensuing discussion here has been fascinating, and I think I've learned more than in any science class I ever took! ( as far as I can remember...the little red schoolhouse ya know!!

Gene,
You better not bail out on us here!!! You have been doing an incredible job of scientific experimentation, I think the first of this type I can recall. What you are doing presents some excellent hands on perspective for some of the somewhat complex ideas that have come up. Thank you for following through on this !!! Outstanding work!

All the best,
Jim

[Jens Nordlunde]

Gene, you are doing excellent with the compasses – tell me did you empty the shop ?
Allow me just one question, when you show the blade with the compasses, it seems as if the magnetism north-south is farther away from each other than the magnets on the knife holder – is that so?

Jens

[Mare Rosu]

JENS
You are very astute MR. JENS
I failed to take a picture of the knife on the magnetic holder at the tip end.
I placed the knife on the holder in two different places that is why you see two areas of magnetic fields and not just the one, both times were approximately five minutes each time with the tip end placement being the last one.
I thing the Case knife picture was different in that the knife profile came out very well while on the Mysore dagger just the magnetic fields are shown.
You ask about the compasses, yes I had to go to two different stores to get them, I tried to get all of them to be the same but could not find four just alike.
One other thing JENS, is that if you look closely at the Mysore dagger with the four compasses on the blade you will see that the tip end compasses is pointing North not South. I do not know why that happened as I did not notice it myself until I posted the pictures, another mystery on the never ending quest for information on Magnetic Weapons!
JIM
I thank you for your comments and will of course stay around as this thread is now becoming a college course for the uninformed (me).
With folks like you and ANN, as well as RIVKIN and I must also add
FEARN for his input/suggestions ( I think he is getting all of his "smarts" from his mother! ) it is hard not to learn from all of this. I also think it is a very interesting subject and not well understood. I do "blame" all of this on JENS, why cant he just read an not ask all of these hard questions?
Gene

[Ann Feuerbach]

This is all such great stuff. It will take me awhile to absorb it all and figure out what it all means! I got someone lined up with homemade ingots any suggestions of how to test them? RIVKIN could you suggest any suitable methods?

[Jens Nordlunde]

Gene, you really had me laugh aloud, I guess that you did not get a discount price, since you had to buy them in two different stores – if you ‘only’ buy two or three compasses a one store, it is harder to discuss the price – although I think a camel dealer would have .

Ann, would it be possible for you to show a picture of one of the ingots?
If it looks like I think, it is like round bread, being thinker in the middle. Would that not make a difference when trying to make them magnetic? Also, if the ingot is round, how would the magnetism be at the ‘sides’? Would it not be different if it is longish ?

Jens

[Mare Rosu]

JENS
I have an wootz ingot and it is round/dome shaped, and I will take a picture of it and I also have a broken flat wootz bar/ingot all gotten from Artzi and I take a picture of that one also.
ANN
let me know what you want me to do as for as applying a compass on them,( I do have a supply of them! )
The bars/ingots have not be subjected to any magnetic fields by me.

I am glad to have you at bat as you sure are one heavy hitter .
Gene

[B.I]

this post is way over my head, but am enjoying the non-participating observation.
dr ann, its great to have someone of your knowledge and passion on board. i am assuming from your article, knowledge and background that your doctrate is related to your current studies. the only reason i ask, is that i have this knee problem in cold weathers....
gene, you dont fail to bowl us over with your ingenuity. not sure what you'll come up with next, but will hide in case there are explosions.
well done jens, for starting and carrying this discussion. i still havent got a clue whats going on but its all fun!

[Ann Feuerbach]

I do not have the ingot...they are in Germany, I think. I was just wondering if they had any natural polarity or magnetic properties. My friend is willing to test them. As I have mentioned before, I have not done any research on this so my knowledge of magnets etc is very limited (for the moment at least). Depending where they were made, the ingots can range from light bulb shaped, to cone shaped, to elongated, to egg like, to puck shaped. Depends on the crucibles interior shape.
Technically my Doctorate is in Archaeometallurgy (the study of ancient metals, yes...obscure). PhD was titled: Crucible Steel in Central Asia: Production, use and origins. So I have been working on the topic for a while, but there is still so much to learn! But I really am more of an Archaeological Scientist, as I also do conservation, glass, glazes, and ceramics...but all this inorganic stuff is the same to me. I don't do bones, so can't help with that knee . I wish I had the money of a medical doctor! I got the same student loan debts as one!

[Mare Rosu]

JENS
Is this the type of wootz ingot you were referring to, the round one?

Ann
you can have both wootz ingots for your testing if you want them, no string attached. and they are here in the USA ( some think Georgia is not however in the USA. but it is ) As you can tell from the pictures that the wootz ingots are neutral with no magnetic fields as all the compasses are pointing North.

B.I.
I thought that JENS was the mind reader of the forum. Your comment about blowing up things. When I left my old Laboratory position and took the chief Health Physic position at a Nuclear Power Plant, my old Plant Manager told
my replacement that " if Gene hasn't blown up he lab by now it will never be blown up", and that sir is the truth! So you also have the mind reading ability!
Gene

[Mare Rosu]

JIM
Way off the subject of this thread however your comment to
Ann about her great writing skills reminded me of a time a long ago when I was involved in helping write a paper on the Nuclear water chemistry at a Nuclear Power plant.
The words that I used were not acceptable, reason was that the paper had to be written to the most knowledgeable person in the field and had to be written "over his head", all for impression sake and not to convey any information/knowledge to the lay public.
Ann has the ability to convey information to us dummies ( me that is) and I thank her as well as you for it, you also have the ability to not only convey information in understandable terms but to also smooth the feathers of the forum folks from time to time.

Will be back on subject matter when I return from taking my wife to the SEC woman's basketball tournment.
Be back next week
Gene

[Rivkin]

Originally Posted by Ann Feuerbach

This is all such great stuff. It will take me awhile to absorb it all and figure out what it all means! I got someone lined up with homemade ingots any suggestions of how to test them? RIVKIN could you suggest any suitable methods?

The problems I see is that:
1. The magnetization depends on two unknown factors - how non-uniform the steel is and what kind of fields the sample was exposed to. Lighting, wielding machines and subways all produce significant fields, capable of magnetizing pieces of iron.

So at least two different experiments should be condacted, unless you are interested in non-uniformities alone. Then the reasonable thing is to ask a steel metallurgist, but I think they actually measure permeability - they take not very large field, apply it to the sample and see what kind of magnetization is produced - it's supposed to be uniform if for example you apply the field along the easy axis (parallel to the sword?), but only if the sample itself is uniform.

Another way is to use X_Ray scattering or conductance or chemical tests - I think all these techniques are been used in the steel industry.

another interesting thing would be to try to achieve the true ground state in the sample by heating it up and cooling it down in the absence of external fields, with probably some random ac fields being applied to the body.

Concerning shape-dependent demag factors, there are programs like rkmag and oomf that allow one to simulate the magnetizations, so you should get the approximate picture of what kind of state you should have.

2. To Mare Rosu:

Thanx for the pictures,
The thing I would consider to be interesting is a conductance test. I don't think it can fire up with a simple resistometer, but it can be that if you place probes at about 5mm from each other on the dagger and move them alongside the dagger's surface that you will be able to see a significant change in the resistance along some set of points, which is possibly can be connected to the changes in the metall itself.

The problem is that not all steels are ferromagnetic, but they are all conductors, so unlike magnetism, you should not see a lot of difference.

P.S. I'm not a steel guy and not an experimentalist, so I really should not give any advices.

Sincerely yours,

K.Rivkin

[Jens Nordlunde]

I always thought ingots were like the round one you show Gene, but after having read Ann’s article in Minerva Magazine No. 13, issue 4, 2002, I was wiser, ingots can be found in many shapes and sizes, the ones made in Merv weighted according to Ann’s article about 2 kg.
Gene how many different ingots do you have, and do they have the same weight?
Is there any writing or marking on them? I remember to have seen a picture of a round ingot with some writing on it.

Ann, do you know if the shape of the ingots was a kind of ‘trademark’ for a region?
Would the kind of clay used, ‘porcelain’ clay vs. other types of clay, have any influence on the ingot?
Maybe we should start another thread on ingots.
Somewhere I saw, that in one of al-Biruni’s (973-1048) books, I think it must be in Kitab al-Hind that he describes iron/iron production(?) in India. Do you know if it is in this book?

Jens

[Mare Rosu]

JENS
This is the link to the wootz bar I had and made it into a Bowie by Al Pendray and also tested by Verhoeven. The end with the inscription is still with Pendray, at least it was the last time I saw him.
http://www.vikingsword.com/ubb/Forum1/HTML/002326.html
Gene

[Jens Nordlunde]

Gene, the ingot you show on the link seems to be round and flat. The one I saw a picture of was shaped like the round one you show on a picture on this topic, but larger - I think. The writing was on top of it, and looked, as I recall it, like the writing on the one you show on the link.

Jens

[Ann Feuerbach]

Thanks Gene for the generous offer! I will take you up on it as soon as I have time to spend doing research. Right now they would just be used as paper weights, until I finish lecturing this term. I will be looking for ingots and blades to include in the book. Where did you get the ingots from?

[Jens Nordlunde]

A small knife I have, in a scabbard together with a katar, is very magnetic, but the katar is not.
The picture to the left shows the tip of the blade, and the one to the right the compass at the base of the blade. The small knife is made in the first quarter of 1600, the katar is newer.

[Rivkin]

When magnetic moments are positioned alongside a line (good approximation for thin swords), there are basically two stable configurations - all magnetic moments are oriented along the line, parallel to each other, or they are all perpendicular to the line, and anti-parallel to each other, i.e. +-+-.

What you have most likely shows that you physically have different steels (most likely phases or chemistry) at the tip and for the rest of the blade, so you've these two macrodomains anti-parallel to each other.

[Jens Nordlunde]

Rivkin, thank you for your answer. I understand what the words, but I have a feeling, that I don't understand the whole meaning. I understand, that when we have come as far as we have, and want to go further, the language is likely to get more complicated. Is it possible for you to explain it in another way?
Here is a picture of the katar and the little knife.

[Rivkin]

In a very approximate manner:

When magnets are dropped into a narrow, long box, they naturally prefer either to align all parallel to each other parallel to the long side of the box, or anti-parallel to each other (with anti-parallel polarities) and perpendicular to the long side of the box. In both cases the magnets will lie parallel to the magnetic field created by other magnets.

So your configuration is most likely due to the case that at the tip you have some anisotropy , most likely due to changes in steel's chemistry or physics (phases).

Just my 2c.