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Old 23rd November 2006, 06:47 PM   #181
Rivkin
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The patterns - no problems. But is it true that their chemistry/structure is usually very different than the swords they were supposed to imitate ? Again, I guess you know this material, while I just read some papers, so I would really appreciate to be corrected here.
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Old 23rd November 2006, 06:48 PM   #182
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Quote:
Originally Posted by Ann Feuerbach
FYI, Personally, I have not come across any blades with Martensite. I would be interested in any metallurgical studies of antique blades that do have Martensite, so references please.
Hi Dr. Feuerbach.

NihonTo (japanese blades) have martensite. A very high quality work my Dr. Tatsuo Inoue
was online but it is now available only downloading it by my site here under the title "Tatsuo Inoue Swordsmithing file":

http://xoomer.alice.it/tsubame/ZZZZZZ_DOWNLOADS.htm

I believe that "Control of inclusions in japanese ancient iron and steelmaking"
(available in the same link) can be of some interest to you too...
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Old 23rd November 2006, 08:50 PM   #183
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Hi

retained austenite is alway a problem with high alloys... especially with chromium.. .. I know Achim made a wootz with stainless levels of Cr ... and he did maintain it was tough... so i don't know .... if you reach the temp for martensite finish ... you should have good conversion... that why i like to undercool my blades abit... (just me being paranoid )


with the martensitic wootz.... you don't have an extended soak time as you would with other high alloy steel... I just treat it as a plain carbon steel with a very short 4 min soak at non-mag... ... basically, i don't want the large macro carbides to go into solution... just the steel matrix..... i know its abit bizarre.... just the opposite of modern heat treatments for high alloy steels... in the modern case you want the carbides to be dissolved
-- take for example A2 .... with 5% Cr needs 30 to 45 min at 1750 to 1800F for proper heat treat....

-- if you think about it..... part of the forging of the barstock is the growth of these macro carbides........ basically dissolving little ones and adding to the big.. .... through all those heat cycles......... from a black heat up to orange etc


also....... alot of the pattern of wootz has to do with how slow the cool time is from liquid charge to solid.... and.... combined with the roast time (anneal ) afterwards.......both time and temperature ...


just my opinion
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Old 24th November 2006, 12:00 AM   #184
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Default Martensite

Can't find better words then the Ted Tenold's ones to describe the following pictures that shows the grouped martensite called "Nie" in japanese swords :

quote...

Nie is basically "spheroidal martensite" which are clumps of martensitic growth propogated by long high heat and maintained in a rapid agressive quench.

...unquote.

pictures by Keith Larman ( http://moderntosho.com ) :



close-close-close up :

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Old 24th November 2006, 01:27 AM   #185
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Hi Ann,

Quote:
Originally Posted by Ann Feuerbach
FYI, Personally, I have not come across any blades with Martensite.
Neither was I aware that they existed until that earlier post by GT Obach and also this paper by Verhoeven and Pendray, available here:

http://met.iisc.ernet.in/~rangu/text.pdf

Quote:
would be interested in any metallurgical studies of antique blades that do have Martensite, so references please.
So would I, but apart from the above, unfortunately I cannot help. I hasten to reiterate that as far as Wootz is concerned, I am a beginner on a steep learning curve.

I imagine that there must have been attempts to quench harden, as opposed to work harden, Wootz blades because of the superior hardness/strength attainable, but we do know the problems associated with quenching hypereutectoid steels. Perhaps quenching from the lowest possible temperature, established empirically would have minimized the problems to an acceptable level. Maybe, by sheer chance every now and then they managed to turn out a martensitic blade that wasn't badly flawed and performed superbly; I just cannot see the ancients regularly turning out superb Martensitic Wootz blades - Just my thoughts as an informed layman on the subject.

If I may impose on you a little: What is the highest measured hardness of a historical blade that you are aware of? And how was it tested (Brinell, Rockwell, Vickers)?.

I suspect that herein resides the original question of this thread. If Wootz swords were not quench hardened, merely work hardened, then I very much doubt that they could have ever been able to cut through armour, never mind wrought iron chains. And as such, whilst serviceable, their legendary reputations must have been based on gross exaggerations.

Cheers
Chris

Last edited by Chris Evans; 24th November 2006 at 01:44 AM.
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Old 24th November 2006, 01:35 AM   #186
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GT Obach,

Thanks for that information. I have no doubt that with modern pyrometry and metallurgical know-how, we can get around the problems of producing Martensitic Wootz that performs - After all, you obviously did, as amply demonstrated by that cutting through wrought iron.

However, the question remains whether the ancients could do the same and to answer this, we need historical samples.

Cheers
Chris
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Old 24th November 2006, 02:09 AM   #187
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Hi Chris

you got it
-- we really need to test more ancient samples..... ... despite the couple studies that were done... i still have hope for some good martensite structures.....(i've been optimistic about it for years...

there are a couple of accounts that talk about oil quenching... ( yes, i know words are not proof enough for either of us...but they are interesting to read. )

Massalski account : "When the blade has cooled, it is quenched in boiling hemp seed oil. Some armourers add a little grease and bone marrow. The wooden tub which contains the oil is sufficiently large for the blade to go in easily. The oil is heated by plunging two or three pieces of red hot iron into it. During this time the blade is given a heat between red and white hot, and then plunged into the bath. If it is a dagger it is held flat; if it is a sabre, it is quenched little by little, beginning by the end of the cutting edge, holding the latter toward the bath. This manoeuvre is repeated until the oil stops smoking, which proves that the blade has cooled. After quenching the blade is always soiled with burnt oil. This dirt is removed by heating it enough to set light to a piece of wood, and by rubbing with a rag from a bedsheet. It is at this time too that imperfections are corrected and the blade is straightened if it is out of true. After 5 or 6 heats the blade leaves the fire quite ready, i.e it then only has to be cleaned with sand, polished with emery and mottled by pickling in iron sulphate. "


I've got others just got to dig them up...

also... one last thing... I'm really not sure that the air quenched wootz would be able to cut a cannon chain... but i could be wrong..... it may cut flesh well but i'm not sure about the other... what i do know is that air cool wootz is much much harder to get a nice even etch on... ...


take care
Greg
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Old 24th November 2006, 02:22 AM   #188
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Hi Greg,

Many thanks for that account. It certainly cannot be ignored and is food for thought as it does support the case for Martensitic Wootz. Not being familiar with the author, when was it written?

As far as work hardened Pearlitic Wootz is concerned, my guess (based on modern similarly hardened products) is that the equivalent of 45Rc should be readily attainable. And this hardness level is that of many 19th century military sabres, so is quite serviceable, but not outstanding.

Cheers
Chris

Last edited by Chris Evans; 24th November 2006 at 03:43 AM.
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Old 24th November 2006, 12:35 PM   #189
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Just as a pointer...

Chris, the text in PDF you linked is not an article from Verhoeven and Pendray, but an extract (only the main text, without the figures, nor the frontpage, foreword and acknowledgements) of a book written by a couple of Bangalore (India) researchers, Dr. Sharada Srinivasan and Prof. Srinivasa Ranganathan, from the National Institute of Advanced Studies and the Indian Institute of Science, respectively. I think these institutions acted as the publishers, also. The title of this work is "India's Legendary Wootz Steel: An Advanced Material of the Ancient World". It was commissioned by the company Tata Steel, and came out in 2004. The rest of the book can also be found in the same page (which is Prof. Ranganathan's, by the way, would anyone be concerned about Intellectual Property issues). The first pages are HERE, and the figures are HERE.

Good discussion, Gentlemen
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Old 24th November 2006, 03:22 PM   #190
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Quote:
Originally Posted by Chris Evans
Neither was I aware that they existed until that earlier post by GT Obach and also this paper by Verhoeven and Pendray, available here:
http://met.iisc.ernet.in/~rangu/text.pdf
Sorry to be a pain, but where in the book do they mention a historical crucible steel blade with martensite? I have had a look and can not find it. Plus is GT Orbach's one from replication or an historical object? I remember doing a survey of all known published historical crucible steel objects, and I do not remember any with martensite, but I could have missed it.

Rivkin, As far as I recall, the information of Anasof's experiments, published by Bogachev, does suggest that his processes were comparable to traditional crucible steel ingredients and processes.
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Old 24th November 2006, 05:41 PM   #191
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Hi

Metallographic examination of two damascene steel blades... by Jerzy Piaskowski... 1978

no mention of Martensite but sorbitic matrix...

SORBITE:

Structure of steel, resulting from the tempering of martensite. In a truly sorbitic structure, the cementite is completely dispersed in the matrix. The trend is to call this structure tempered martensite.

this can be confusing... because i don't know if people still use that term sorbite... .. i know the bladesmiths all call it tempered martensite..


Look on pg 9 in the " discussions "
-- the structure of both blades is very uniform along the whole of the cross-section. The measurements of hardness showed identical values for each of the swords which, in turn, points to the fact that the blades were subjected to quenching and tempering, according to the descriptions by J. Barker and Massalski, who travelled in the Near East.


so... .. I was wrong...... as their is some evidence.....

thank you...



Greg



another quote from the study..

" strips of carbides are visible to the naked eye on the blades surfaces and appear in the form of light coloured bands typical of the damascus pattern, whereas the dark background of this pattern forms a sorbitic matrix "

Last edited by Gt Obach; 24th November 2006 at 06:25 PM.
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Old 24th November 2006, 07:55 PM   #192
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Quote:
Originally Posted by Gt Obach
this can be confusing... because i don't know if people still use that term sorbite... .. i know the bladesmiths all call it tempered martensite.
You're right. Sorbite is martensite tempered at high temperatures (600)
for quiet a long period and is known as tempered martensite.

Hereunder two exaples from my HD :

Typical structure of oil quenched martensite :



Sorbite (martensite quenched in oil and tempered at 600 C for 2 hours) :

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Old 24th November 2006, 11:34 PM   #193
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Very interesting. I thought for example Anosov used graphite instead of traditional materials such as coal/wood. But taking in mind that I have no idea how smithing works, it well may be that I am saying that simple shocks the present in its ignorance .
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Old 25th November 2006, 12:50 AM   #194
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Quote:
Originally Posted by Rivkin
I thought for example Anosov used graphite instead of traditional materials such as coal/wood.
Usually graphite is found in cast (pig) iron being connected with a too much
high carbon content (2,8%-3,8%). I wonder if the burning of graphite
in these experiments can be connected with transferring some carbon to
steel or simply because it achieve the needed temperature in a faster
way or it can hold such temperature longer (only supposing about these two
last properties of graphite).

Japanese smiths transfer carbon to the blade using vegetal fiber wrapping
in certain stages of the smithing. Might be that putting steel into a
burning graphite bed is intended to the same aim to compensate the
carbon loss during the smithing ? Are wootz/crucible steel blades
folded many times as the japanese ones, meaning a loss of carbon in the
process and so needing a trick to maintain high the carbon content ?
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Old 25th November 2006, 06:13 AM   #195
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Hi Ann,

Quote:
Originally Posted by Ann Feuerbach
Sorry to be a pain, but where in the book do they mention a historical crucible steel blade with martensite? I have had a look and can not find it. Plus is GT Orbach's one from replication or an historical object? I remember doing a survey of all known published historical crucible steel objects, and I do not remember any with martensite, but I could have missed it. .
First I must thank Frank for his correction and the supplementary links.

I found that link late in the night and read it too hastily. The authors were most certainly not by V&P - My mistake, for which I apologize.

In my haste, I did not read the work in full, just did a global search for the words `quench' and `Martensite'. However, it appears to me that the author links the hardening of Wootz with quenching and tempering, but I add, none too clearly for me, especially when we get to Pg 87.

On page 29/90 under the heading of Steel Processing: Reference to Indians smiths quenching swords into banana trees and worse

Pg 86/90: Reference to work by Kochman and colleagues in which a historical blade was examined for microstructure and bits of Martensite were found. The full article can be read here:

http://www.crystalresearch.com/crt/ab40/905_a.pdf

I found it interesting that: a) Martensite was formed in the 1st place, as this usually requires quenching of some sort, b) that there appears to be little Cementite near the very edge and c) the rather obtuse angle of the edge, which suggests something or another.

Pg 87/90: Elaboration on the idea of high carbon Martensite decomposing.

Cheers
Chris

Last edited by Chris Evans; 25th November 2006 at 06:42 AM.
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Old 25th November 2006, 03:07 PM   #196
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Thanks loads Chris for the link. I did not have a copy of the article.
Ok, let me add some more murkiness to the mud.....

From Samuel's Optical Microscopy of Carbon Steels, 1980, ASM, P 26-28.
"Sorbite....It was subsequently shown that these constituents often were merely fine lammellar pearlite, but unfortunatly the terms were also indiscriminately used to refer to tempered martensite. This duality or origin was in fact recognized in the original ISI definition......." The text goes on in detail (sorbite was named for Sorby if anyone is interested).

From what I gather, there is primary and secondary sorbite: Primary from the eutectoid transformation process (and perhaps very important for pattern discussion) and secondary sorbite which is tempered marteniste.

Now all that said, my brain hurts and I am no more the wise.
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Old 26th November 2006, 12:19 AM   #197
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Hi Ann

yes.. you are correct and note... that it seems that sorbite... is a confusing term.. ... due to it being used for both tempered martensite and pearlitic sorbite ...

i've read more that a couple times that its an old term that seems to be out of style...lol

I had to reread that study i quoted several times before i realized they were talking about tempered martensite...... the term sorbite had fooled me at first

you see... he mentions sorbite that is produced in the case of these two swords were made according to the Massalski and Barker accounts..... In the Massalski account ... this is definitely an oil quench and that would make martensite ...

if it was pearlitic sorbite... then you wouldn't need an oil quench nor a temper cycle afterwards....... just air cooling


Greg
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Old 26th November 2006, 04:58 AM   #198
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Hi Folks,

1. I am beginning to think that we are rapidly reaching an impasse because of a lack of what can be considered sufficient studies on enough samples to be representative of Wootz swords - Especially those that were more than just eye candy. Nevertheless, we can state with some confidence the following:

a) In the absence of new knowledge, the quench hardening of hypereutectoid (>0.8%C) Wootz would have presented the ancients with enough problems to render the process quite haphazard - Whilst it is conceivable that some smiths could consistently estimate the lowest Austenitization temperature by the colour of the heated steel, a bit too much heat and some of the carbides re-disolved leading to retained Austenite after quenching (very undesirable);

b) That whilst unquenched hypereutectoid Woots can be work-hardened, the hardness obtainable would have been insufficient to produce swords capable of cutting through armour, or for that matter, knives and tools (say woodworking or stone cutting) with a sufficiently keen/hard edge to be truly functional;

c) Quenching/tempering and the attendant superior qualities thus attainable were sufficiently well known in antiquity, for Indian and Middle Eastern smiths to ignore and be satisfied with the inferior alternatives; And

d) there are too many instances of quenching being mentioned in olden times.

2. Other thoughts on this matter:

Why are we concentrating on hypereutectoid Wootz and exclude hypoeutectoid (<0.8%C) as representative of the kind?

What I am getting at is that there is no real difficulty in obtaining excellent Martensitic steel from hypoeutectoid stock, and tempered Martensite is the preferred microstructure for a sword that cuts by impact.

If the Indians could reliable produce hypoeutectoid crucible steel then the problem of how to obtain truly great hardness&toughness disappears. I imagine that it may have even been possible to arrive at a hypoeutectoid steel by de-carburizing hypereutectoid crucible steel stock. At this point of my deliberations, the only real advantage that I can see for hypereutectoid Wootz, apart from appearance, is a lower melting point which facilitated the crucible reduction process.

Greg could be right, as per his posts elsewhere, that our current day definition of what constitutes Wootz is unreasonably narrow by restricting it to hypereutectoid steel. For example, Vehroheven&Pendray decided that one of the swords they studied was not Woots Damascus because it did not contain the expected carbides. Ands yet, the term Wootz is said to be the Anglicization of the Kannada word for steel (any steel or crucible steel?). Of course they added the appellation `Damascus' to their definition, but then why go looking for mechanical attributes that may have have been the property of swords exclusive to this definition?

I think that it is fairly safe to say that when ancient chroniclers recorded that some swords performed remarkable cutting feats, that they did not class them by their carbon content, rather their origin, and even that very broadly.


Cheers
Chris
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Old 26th November 2006, 06:04 PM   #199
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Hi Chris,
You are right. I have been arguing that hypoeutectoid crucible steel (producing ferrite/pearlite banding pattern) should not been seen as inferior. I am SURE that both were made in the same workshop, and were in the furnace next to each other, to control a difference between >0.8% and <0.8% would have been difficult to control. I am sure that cast iron was occasionally made as well.

Also, when I did my PhD I found that only 18 blades had been studied, which is why I am trying to increase that "database". How can we base any theories on such a small sample base? Plus, where the sample was take on the blade is also a concern when it comes to microstructures etc.

Just a note to say that I am not against any quenching/tempering of ancient blades, just the lack of evidence, but as mentioned above, could be due to sampling.
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Old 26th November 2006, 07:27 PM   #200
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Hello,

This is a wonderful discussion, thanks to all the metallurgists for the great information!

In "Armes blanches du monde Islamique" by Alain Jacob, I think, I recall an account by a French officer in Napoleon's army who commented on Mamluk sabres. He gave an account of the way Mamluks trained: they would ride at full speed towards a block of wood on which was placed a turban. They would have to slice the turban in half without displacing it off the block, careful not to hit the block of wood as it would break the sword and cause great shame. I don't recall if he characterized the blade as Damascus, but the passage indicates that these blades could hold a magnificent edge, but were extremely brittle. Would such blades exhibit a high austenite content?

Regards,
Emanuel
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Old 26th November 2006, 10:06 PM   #201
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Quote:
Originally Posted by Manolo
Hello,

This is a wonderful discussion, thanks to all the metallurgists for the great information!

In "Armes blanches du monde Islamique" by Alain Jacob, I think, I recall an account by a French officer in Napoleon's army who commented on Mamluk sabres. He gave an account of the way Mamluks trained: they would ride at full speed towards a block of wood on which was placed a turban. They would have to slice the turban in half without displacing it off the block, careful not to hit the block of wood as it would break the sword and cause great shame. I don't recall if he characterized the blade as Damascus, but the passage indicates that these blades could hold a magnificent edge, but were extremely brittle. Would such blades exhibit a high austenite content?

Regards,
Emanuel
Emanuel, have you realized that hitting a wooden block at that speed would have meant to cut into the block itself making angled leverage on the blade during the very few seconds of gallopping away ? This would break *every* sword or bent a too soft one. Never cut, eh ?
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Old 26th November 2006, 10:22 PM   #202
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Quote:
Originally Posted by Manolo
Hello,

This is a wonderful discussion, thanks to all the metallurgists for the great information!

In "Armes blanches du monde Islamique" by Alain Jacob, I think, I recall an account by a French officer in Napoleon's army who commented on Mamluk sabres. He gave an account of the way Mamluks trained: they would ride at full speed towards a block of wood on which was placed a turban. They would have to slice the turban in half without displacing it off the block, careful not to hit the block of wood as it would break the sword and cause great shame. I don't recall if he characterized the blade as Damascus, but the passage indicates that these blades could hold a magnificent edge, but were extremely brittle. Would such blades exhibit a high austenite content?

Regards,
Emanuel
Hi Manolo,

this practice technique is in the furussiya manual, and is the basis of mounted sword use. It advances onto a stage where a mamluk has to cut his way through a series of turbans, not just one, on his left and right. The manual also states that training swords, and I assume, the ones used here are, incredibly sharp and brittle, but are not to be used in real combat.
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Old 26th November 2006, 10:47 PM   #203
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Carlo and Saqr, thanks for your replies.

The short passage concerning this training exercise had merely stated that the sword would break -presumably on impact...I really don't recall its details but I will get the book from our library and read it again.

You're right about the angled leverage Carlo, and I understand it. Lateral stress can easily snap metal, one can even break some bars over one's head assuming proper training.
My thought was in regards to the discussion in this thread about wootz swords cutting through armour and chains. "If a sword were to snap on a direct edge impact with hard wood, how could it withstand metal?" I thought. But since we are talking of different swords for different purposes, the question is moot.

Emanuel
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Old 27th November 2006, 03:47 AM   #204
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Hi Manolo,

Quote:
Originally Posted by Manolo
..... Would such blades exhibit a high austenite content?
Thank you for your appreciative words. I think that both Ann and Greg,as well as the others deserve a special thanks for their extermely valuable contribution. I certainly learned a lot about Wootz from this thread.

Now for your question: It is hard to explain all the ins and outs of the heat treatment of steel within the constrains of a thread like this, but I'll try, albeit at the risk of oversimplification.

Carbon steel at room temperature consists of a mixture of near pure fairly malleable iron, known as Ferrite, and very hard iron carbides, known as Cementite. In this state, steel is moderately soft and can be bent and worked fairly easily.

Hardening by Quenching and tempering:

Steel is heated to a temperature at which its crystal structure changes and becomes as soft and malleable as lead. This structure is called Austenite and it can dissolve all of the carbides that we mentioned above, forming a solid solution of carbon in iron. Here I should mention that solids can dissolve in other solids, not just liquids - Hard to believe, but the process is complex and you'll have to take my word for it.

When heated Austenitic steel is rapidly cooled, as when quenched in water, the carbon cannot come out of solid solution, as it would under slower cooling, and the Austenitic crystal structure changes to one that is very resistant to deformation, on account of the carbon atoms trapped in it.

This new crystal structure is called Martensite and it is very hard and brittle.To render it usable, it is usually tempered by reheating, so as to allow some of the carbon atoms to come out of solid solution and thus reduce both its extreme hardness and brittleness. The carbon that is thus removed from the Martensite forms tiny spheroids of Cementite and results in a structure sometimes known as Sorbite, but more commonly called tempered Martensite. If Martensitic steel is tempered at high temperatures for a very long time it reverts to its original unhardened structure of Ferrite plus Cementite.

OK - Those are the raw basics. Now for the problems.

Plain carbon steel (without additional alloying elements) with less than about 0.4%C cannot be cooled fast enough to transform the Austenite into Martensite, but between 0.4%C and 0.8%C there are no great problems.

However, once the carbon content exceeds 0.8%C, known as the eutectoid composition, then upon quenching the tendency of the Austenite is to stay as it is and not transform into Martensite - Contrary to its usual high temperature `habitat', this Austenite remains as such at room temperature and is known by metallurgists as `retained Austenite', that is retained after the quench.

If we quench hypereutectoid steel (>0.8%C) not all of the steel remains as Austenite. In practice, depending on by how much the 0.8%C is exceeded, we tend to get a mixture of Martensite (hard and brittle) together with retained Austenite. Now remember that as I said at the start, Austenite is very soft and malleable. At the risk of gross oversimplification, now you should think of the retained Austenite as if it wasn't there, because it is so weak. The net result is a Martensitic sword blade with what amounts to all intents and purposes as `strength gaps' all over and inside it. Really disastrous for strength. Of course, the real picture is more complex, but at this level we need not overly concern ourselves with metallurgical minutiae.

In the heat treatment of modern high carbon steels there are strategies to minimize the problem posed by retained Austenite; For example with cutlery high carbon stainless steels such as 440C, any retained Austenite is converted into Martensite by cooling to very low temperatures.

However, the ancients, not understanding what went on inside the steel, would have had only two options (that I can think of):

a) Stick with hypoeutectoid steels (0.4%C-0.8%C), not easy to do as they could not analyze for carbon, nor knew about its critical role; And

b) if having to heat treat higher carbon content steels, they would have had to be extremely careful to quench from the lowest possible temperature at which Austenite forms. This so as to minimize the dissolution of the segregated carbides back into the Austenite and thus raising its carbon content, which would lead to retained Austenite. I imagine that by trial and error this temperature could be judged by the colour of the hot steel, but my guess is that they would have turned out a lot of bad blades.

I hope that this helps. If you would like to obtain more information see the entries in Wikipedia, as it gives a fairly good account.

I also hope also that you can see why the manufacture of a well hardened sword was more often than not a stroke of luck and why such swords had such exalted and legendary status.

Cheers
Chris

Last edited by Chris Evans; 27th November 2006 at 09:08 AM.
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Old 27th November 2006, 03:52 AM   #205
Andrew
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Great discussion, folks. Many thanks.
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Old 27th November 2006, 06:48 AM   #206
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Quote:
...they could not analyze for carbon, nor knew about its critical role;
I think we have to be careful here: yes, they did not have a scientific understanding of carbon and it's specific role in how steel behaved in the quench. However, they had generations of empirical knowledege that said things like 'steel that looks like this, behaves like so;' to such a degree that when metallurgy and metallography became the way to understand steel they were checking the new theories against the eyeballing of fracture surfaces by the old foundry guys. They could give you the carbon content down to tenths of a percent or better just by looking at a quenched and broken surface. All that knowledge dissappeared in the last hundred years, but I think it's safe to assume it went back a thousand or more, and they had a good idea of how to treat the hypo- and hyper-eutectoid steels as they came from the furnace, if not precisely why.
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Old 27th November 2006, 08:02 AM   #207
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Hi Jeff,

Quote:
Originally Posted by Jeff Pringle
I think we have to be careful here: yes, they did not have a scientific understanding of carbon and it's specific role in how steel behaved in the quench. However, they had generations of empirical knowledege that said things like 'steel that looks like this, behaves like so;' to such a degree that when metallurgy and metallography became the way to understand steel they were checking the new theories against the eyeballing of fracture surfaces by the old foundry guys. They could give you the carbon content down to tenths of a percent or better just by looking at a quenched and broken surface. All that knowledge dissappeared in the last hundred years, but I think it's safe to assume it went back a thousand or more, and they had a good idea of how to treat the hypo- and hyper-eutectoid steels as they came from the furnace, if not precisely why.
I absolutely agree with you that they had lots of empirical knowledge, but perhaps not quite as much as we may think. I am open to be persuaded to the contrary, but would like to know more of their methods.

All the same, they were very good. For one, I never cease to be astonished as to how Japanese swordsmiths managed to identify the high carbon steel for the edges - It was done as you say, by breaking bits of steel and examining their surface. However, we must remember that good steel or swords were the exception and not the rule, which strongly argues for a lottery factor in their methodology.

Carbon was identified as an element at the end of the 18th century and from that point on the metallurgy of steel advanced in leaps and bounds. Once an accurate analysis could be made, all sorts of indirect qualitative tests could be standardized against laboratory results and this is how those very savvy tradesmen did their seemingly unbelievable assessments. For example, if one has a good collection of steel samples of known composition then with a simple grinder spark test one can identify an unknown sample with astonishing accuracy. But without those reference samples it becomes much more difficult.

With bloomery steel made by solid state reduction, the resultant was nearly pure iron which had to be carburized. This was done by heating in a carbon rich environment and the iron absorbed the carbon. My suspicion is that although they did not know what exactly they were doing, they could correlate the end result with carburization time. But in the absence of accurate temperature and furnace atmosphere control, it must have been an uncertain process.

Here is an interesting link onto 18th century steel making:

http://www.staff.hum.ku.dk/dbwagner/....html#Heading1

Cheers
Chris
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Old 27th November 2006, 01:35 PM   #208
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And of course their were good smiths and less good smiths. Plus add in those who have been working along with their father since they were very young, or at least around 12 years old, they would/could have a great amount of hands-on knowledge passed down for generations. Whereas others, may not have had as good training, didn't care, or simply weren't that talented.
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Old 28th November 2006, 05:47 AM   #209
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Hi Ann,

You make very valid points. The quality of smithing must have varied enormously.

As well, we must remember that in the absence of patent rights, the empirically hard won advances were jealously guarded and not shared as we might expect. There is the story of the Japanese swordsmith's apprentice who put his hand in the quenching water and had it cut off by his master. Perhaps apocryphal and with different interpretations as to why the youth was treated so savage; But a Japanese friend, also a metallurgist and very knowledgeable on their sword making opined that probably the young man was trying to find out the temperature of the quench water, something that his master wanted to keep a secret.

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Chris
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Old 29th November 2006, 03:29 AM   #210
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Hi Folks,

I would like to draw your attention to two most interesting pos by Zifir (22&25) under the thread of Fencing With Sabres. He presents quotes from William Elton, esq., A Survey of the Turkish Empire, London, Printed for T. Cadell, jun. and W. Davies, 1799. on Turkish sabers.

It states that Turkish swords were both hard and brittle, capable of cutting through an iron nail thick as a finger, and strongly suggesting that they were hardened by quenching and tempering.

Cheers
Chris
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