Viking Swords and Wootz

[katana]

Hi everyone,
read this brief article which you may find interesting....

http://www.guardian.co.uk/science/20...-vikings-sword

Wootz, Fakes and burial swords ....plenty for a discussion

Happy New Year

Regards David

[Pukka Bundook]

Hi David, and;
Happy New Year!

Yes, I read this somewhere recently.
It appears even the genuine blades were made over a few generations.

Only thing I question here, is there seems to be the idea that the 'Vikings' made these swords, and I think it has been established beyond serious doubt that these blades are Frankish.
Still, I was not aware that the Franks or whoever were using crucible steel.
Are not the Vlfberht blades made with a pettern-welded core?
...would appear unnescessary with crucible steel.

I find it very refreshing, that new information is still forthcoming!

All the best,

Richard.

[Richard Furrer]

Hello All,
This will be rough, but its from memory.

I can not speak for Dr. Williams, but I was in India when he first presented this paper in 2007 (later published in Gladius I think). It is my recollection, as I do not have the paper in front of me, that Dr. Williams tested 13? Ulfberht blades of the 30-60? known and four or so (all with "Ulfberht" spelled the same by the way) turned out to be slag free in the body of the blade and it is this lack of slag and the carbon content which led to the idea that it was forged from a crucible steel product. I can see no flaw in that argument.
The only other way to obtain slag free steel is to be lucky enough to have some form as a liquid in the bottom of an open reduction process and use this to forge a sword, but I have not ever seen a large enough single piece to make a sword (a small knife perhaps, but not a sword). There was no evidence of a weld line in the slag free blades tested...this does not mean that there was no weld, but id does mean that none was seen. I would think that this could be proven one way or another by sectioning the entire blade in many directions, but I doubt this would ever be allowed to occur.

Where the crucible steel came from is up for debate as it is almost impossible to trace the origin of such things.

BUT,
The article referenced above is more sensational then the original as one would expect such in a popular newspaper.

Do keep in mind that Dr. Williams also gave us the "Knight and the Blast-furnace" some years ago...which was no small task either.

What this slag free finding shows me is that the old smiths were far more clever then we think and perhaps trade was far more widespread then what was previously assumed. This also illustrates the matter of discovering craftsmen's work and viewing it with tools which allow us to appreciate their accomplishments.

Ric

[kisak]

I wonder a bit about the "fake" part. While such most likely did exist in considerable numbers, I wonder if we can really with just this rule out that Ulfberth made swords from local steel as well, perhaps when there wasn't enough imported steel to be found, or perhaps as the "budget line".

A very interesting discovery in any case.

[Lee]

Williams, Alan R., 'Crucible Steel in medieval swords', Metals and Mines: Studies in Archaeometallurgy (London, 2007), pp. 233 - 241.

ULFBERTH will be spelled various ways between different examples; apparently those with high carbon content and a microstructure suggesting crucible steel have, so far, all been spelled the same way. Exciting stuff; I am most curious to see what trend emerges as more swords are analysed.

[Gonzalo G]

The article seems incongruent to me, but I have no much knowledge of the subject. Swords made with iron would not shatter like that, unless having many impurities and inclusions, and hardening them in cold water would give only a very small hardness to the iron. On the other side, they don´t mention "wootz", only crucible steel. Swords were made with crucible steel not being wootz, but with this carbon content they would be very brittle. I understand that toughtness of wootz with it´s carbon content is due to the fact that it has a perlite matrix. The "Viking solution", as I recall, consists in making blades with an iron body, and only the edges, mechanically welded to the body, were made of steel. That would not make a fragile blade. Please correct me if I am wrong.
Regards

Gonzalo

[Jeff Pringle]

Like most newspaper items on esoteric subjects, there is often a bit (sometimes quite a bit ) of error introduced between the interview and the page, so don’t be surprised the facts seem ‘off’ in the Guardian article.
The Viking period spans a few hundred years, and the era includes some pretty radical improvements both in sword design and in steel making, so it would be a mistake to think there was just one way to make a sword during that era. Plus, swords made locally vs. swords made in an ‘industrial’ center & exported will add a layer of difference.

You can get more info on the fake issue and start forming your own theories on which ones were ‘fake’ from reading “The Vlfberht sword blades reevaluated” by Anne Stalsberg, she did a signature analysis of ~135 Ulfberhts, and there are two variants of the signature (the two most numerous) she concludes are probably authentic.

Below is a Williams quote from 2003, when he was starting to develop this concept - note he is saying higher slag content (not quenching!) can lead to brittleness:

Some early medieval swords in the Wallace Collection and elsewhere
David Edge, Alan Williams
Gladius XXIII, 2003 pp. 191-210
http://gladius.revistas.csic.es/inde...rticle/view/50

“….
It should be observed that yet another blade with a similar inscription has been found by one of the authors to consist of a totally different metal. That «Ulfbehrt» sword was made of an air-cooled hypereutectoid steel of around 1.0%C (Williams, 1977). Since that account was published, a great deal more information has become available about the crucible steel industry of Central Asia (e.g. Craddock, 1995 and Feuerbach, 1997) and it seems likely that a cake of such a steel was the raw material for that blade; being virtually slag free and of hardness around 300 VPH, it must have been an exceptionally serviceable sword, and one which would keep its hard edges permanently. The maker of our «Ulfbehrt» sword had made what must have seemed to his customers at the time like a very good copy, with an edge hardness of over 460 VPH. Prolonged use might have altered their opinions; the cutting edge is only 6mm deep, and could have been removed by a few years of regular sharpening on a grindstone. It is also distinctly higher in slag content, and therefore more likely to fracture on impact.
….”

[Gonzalo G]

Jeff, thankyou for your information on this subject, and also on the wootz thread. I found very interesting and useful your comments.
Regards

Gonzalo

[Chris Evans]

Hi Jeff,

Originally Posted by Jeff Pringle

... It is also distinctly higher in slag content, and therefore more likely to fracture on impact.
….”

Informative post.

Without knowing much about Wootz, in wrought iron slag inclusions enhance toughness by acting as a crack arrestor. It is my understanding that the core of Japanese swords is often high in slag content with a similar effect.


Cheers
Chris

[Jeff D]

Originally Posted by Chris Evans

Hi Jeff,



Informative post.

Without knowing much about Wootz, in wrought iron slag inclusions enhance toughness by acting as a crack arrestor. It is my understanding that the core of Japanese swords is often high in slag content with a similar effect.


Cheers
Chris

Hi Chris while awaiting the correct answer from the other Jeff, here is what I think. Slag in well worked steel forms long thin strings "stringers" which will give the effect you mention. In wootz working the steel in a similar fashion would eliminate the watered pattern. Therefore large (unworked) inclusions of slag would provide a fracture line.

Hope I am correct
Jeff

[Chris Evans]

Hi Jeff,

Originally Posted by Jeff D

Hi Chris while awaiting the correct answer from the other Jeff, here is what I think. Slag in well worked steel forms long thin strings "stringers" which will give the effect you mention. In wootz working the steel in a similar fashion would eliminate the watered pattern. Therefore large (unworked) inclusions of slag would provide a fracture line.

Hope I am correct
Jeff

What you say is correct. However, If I read it correctly, that quote about slag was referring not to a Wootz blade, but to a local copy. As such it would have been made from sponge iron and hammered extensively giving rise to the elongated stringers of slag, which rather than detracting from toughness probably would have had the opposite effect.

Cheers
Chris

[Jeff D]

Hi Chris,

Thanks for your reply. You are correct they are taking about crucible steel not wootz. There has been a trend in using the terms interchangeably although they are different. I interpreted your question wrong. Now that I think I know what you are asking. I suspect it is the lack of hammering of the fakes that would be the problem, hammering that would not be required on crucible steel. I know you know this much better than me. Do you mind me asking, doesn't it takes multiple foldings to form the stringers, not just hammering to shape?

All the Best
Jeff

[Chris Evans]

Hi Jeff,

Originally Posted by Jeff D

Hi Chris

Do you mind me asking, doesn't it takes multiple foldings to form the stringers, not just hammering to shape?

All the Best
Jeff

Sponge iron has to be hammered extensively every which way to reduce its slag contents (by squeezing it out) - This is done as a matter of course. And the extent of hammering it receives ensures to a considerable degree its quality, though not entirely.

Without knowing the answer to your question, it is my view that some folding would have been unavoidable. But whether the ancient Viking swordsmiths went as far as others, say the Japanese, in the pursuance of refinement by way of repeated folding, I cannot say. I think that a much hammer refined blade would have represented a superior product, and this simply on the basis of labour input. Just how aware the Viking swordsmiths were of the need for extensive hammer refinement of sponge iron, I am ignorant of and here we need a knowledgeable archeological metallurgist, something that I am not.

However, I'll venture to question the presumed superiority (in the article) of a Wootz blade against one well made from sponge iron and hardened. If the ancients could quench and temper Wootz, then they indeed would have had a superior blade, but that would have required being able to heat just sufficiently to austenitize the pearlite without dissolving the carbides and then quenching, a task requiring very good temperature control, not to mention knowledge. On the other hand, steel made from sponge iron can be quenched and tempered with relative ease - This is how swords, indeed all steel implements, were made before the advent of molten steel making, and we do know that perfectly serviceable and many excellent blades were produced this way.

In a past thread we have discussed whether Wootz was quenched and tempered in the old days, and there is some evidence that some of it was. As to how they went about this and how successful it was I am not sure - Without having done any first hand experiments, or reading of any such attempts, my guess is that if high carbon Wootz is heated to the extent that a substantial amount of the carbides are dissolved, then upon quenching and tempering its microtructure would turn into a proverbial dog's breakfast with very uncertain mechanical properties.

Cheers
Chris

[Jeff D]

Hi Chris,

Thank you for your answer. Regarding the quenching of wootz, what do you make of this. Sorry this is the best picture I could make.

Thanks again
Jeff

[Chris Evans]

Originally Posted by Jeff D

Hi Chris,

Thank you for your answer. Regarding the quenching of wootz, what do you make of this. Sorry this is the best picture I could make.

Thanks again
Jeff

Hi Jeff,

Interesting photo. Edge appears to be heat treated - Am I right?

If so, this could have been a means of countering the negative effects of dissolution of carbides, as the unhardened spine would have retained sufficient strength to render the blade serviceable. I wonder how they would have quenched the edge only of a deeply curved blade ...What would be really informative is to take a cross section of the blade and examine its microstructure......

This is pure speculation on my part, but another way of hardening Wootz would have been to decarburize the steel by prolongued heating in an oxidizing atmosphere to reduce its carbon content and then, after a process of homgenization by hammering and folding, quenching and tempering - The obvious difficulty would have been knowing when to stop the decarburization process.

Cheers
Chris

[Jeff Pringle]

Whoa, you guys type faster than I do!
This repeats some of what Chris just stated, with a different spin...now I got to go think about heat treating...
Wrought iron and steel are very different animals, I do not think it is advisable to extrapolate from one to the other. What might be a welcome crack arrestor in iron could be an unwelcome stress riser in steel.
The slag stringers are a natural outcome of the method used to refine freshly smelted bloomery/tatara iron and steel, repeated folding, which has the primary purpose of removing the slag and homogenizing the metal. The more folding done, the less slag there is and the grain of the slag inclusions becomes finer. The edge of a sword would be severely compromised by a large slag stringer crossing there, or in the metal just behind the edge, so the metal used there is more refined. In the body of the sword, supported by more surrounding mass and not at the stressful cutting edge of the blade, such a degree of refinement is not needed so they used material that had less labor and materials invested in it. The slag stringers are in the middle because it is a more efficient way to make a blade and they can do no harm there, no other argument is required. This Moro spear nicely illustrates the technique.
The wootz/crucible steel method trades in the ‘repeated folding’ refinement for a liquid separation, but the goal is the same - homogenous metal and little or no slag.
It is entirely possible that the Ulfberht Co. got a nice price on imported ‘pre-refined’ steel for a couple years and when the economic situation shifted they continued on with the usual stuff, but I have yet to read the Williams article and see what it actually says. The Guardian article is goofy, but a good conversation starter!
Here’s another +Ulfberht+ (as opposed to +Ulfberh+t) analysis -
http://fornvannen.se/pdf/1980talet/1981_024.pdf
Metallografisk analys av inläggningar i vikingatida svärdsklinga,
inv. nr SHM 907 Go, Hogrän sn, Ålands
Av Mille Törnblom

[Chris Evans]

Hi Jeff (Pringle),

Thanks for your very informative post, to which I can add nothing of significance. Any chance of a rough translation of that most interesting article, just to get the gist of it? And as someone who has had a fair bit to do with Wootz, could you shed some light on its historical heat treatment as uncovered by modern research, is such information exists?

Cheers
Chris

[ward]

Happy new year

Little different direction in this article
http://www.physorg.com/news150373962.html

[Jeff D]

Thank you Chris and Jeff.

Excellent explanation guys but, I think I may be missing something here. Is the central core wootz or crucible steel (on the real deals)? Just so that I am on the same page, my understanding is that wootz is crucible steel with a surface pattern, correct? Why would tempering crucible steel be any different then forged or case hardened steel?
Tempering wootz would obviously be a much bigger problem if the surface pattern is to be maintained. I have posted the picture of what I believe to be a temper line with an intact (but altered) surface pattern, to show that it could and was done.

Thanks guys!
Jeff

[Gonzalo G]

Originally Posted by Chris Evans

Sponge iron has to be hammered extensively every which way to reduce its slag contents (by squeezing it out)

However, I'll venture to question the presumed superiority (in the article) of a Wootz blade against one well made from sponge iron and hardened.

In a past thread we have discussed whether Wootz was quenched and tempered in the old days, and there is some evidence that some of it was. As to how they went about this and how successful it was I am not sure - Without having done any first hand experiments, or reading of any such attempts, my guess is that if high carbon Wootz is heated to the extent that a substantial amount of the carbides are dissolved, then upon quenching and tempering its microtructure would turn into a proverbial dog's breakfast with very uncertain mechanical properties.

Cheers
Chris

Chris, I am confused by your words. I understand that old steels were made with bloomery iron, and not sponge iron. Or instead, decarburizing cast iron with high carbon content, which is more easily molten at lower temperatures. Sponge iron, as I understand it, is another kind of product. I feel much of the discussion about wootz is biased by speculations which tend to maximize, or instead, minimize, the value of this type of steel, making statements above of the facts. It is scientifically healthy to have some dose of scepticism in front of myths and distortions. But the fact is that we don´t have enough samples of wootz blades, studied and tested, and even less scientific comparisons among wootz blades and european blades from the same period. On the other side, it seems that there is another manuscript from Al Kindi dedicated to the thermal treatments of the blades made with wootz, which is not yet printed, though I understand maybe there is already an italian traslation. There are references to this work on the book Medieval Islamic Swords and Swordmaking, by Hoyland & Gilmour.

But even with the publication of the translated manuscript, I belive we will yet have many questions for years to come about this subject. I hope the archaeometallurgy helps us in the progresive clarification of many of our questions. Other discoveries look ahead on the study of the traditional swords of the world, as the viking swords seem to demonstrate. I still believe the articles about viking swords refer to a relatively clean high carbon crucible steel, and not to wootz. The swedish article mentions the presence of 0,8% refined carbon steel in one of the edges of the studied sword, and 0,4 to 0,6% carbon steel on the other edge. This opens the possibility of speculate about some specialization among the different edges of the viking swords, or at least in some of them, but it is only a good? pretext to continue our conversation. Some of the viking swords seem to be very complex in their structure, not because they are multilaminated in the japanese way, but because they have many different types of steels and irons in their composition, all welded in the make of the blade.

This kind of solution is not less sofisticated, or work intensive, than the japanese nihonto, in my opinion, but this is said with no regard of the differences on their success to have the best relation metallurgy-geometry-design, or to do with more effciency the expected job, as it is another very difficult subject to discuss with some scientific basis. Of course, this are only some of my ideas, and I can be wrong.
Regards

Gonzalo

[Chris Evans]

Hi Gonzalo,

Originally Posted by Gonzalo G

Chris, I am confused by your words. I understand that old steels were made with bloomery iron, and not sponge iron.

The stuff that comes out a bloomery is sponge iron, a miture of iron and slag. See http://en.wikipedia.org/wiki/Bloomery.

Or instead, decarburizing cast iron with high carbon content, which is more easily molten at lower temperatures.

That is another way of making steel, but it's a later development. See
http://en.wikipedia.org/wiki/Steel#Ancient_steel

I feel much of the discussion about wootz is biased by speculations which tend to maximize, or instead, minimize, the value of this type of steel, making statements above of the facts. It is scientifically healthy to have some dose of scepticism in front of myths and distortions. But the fact is that we don´t have enough samples of wootz blades, studied and tested, and even less scientific comparisons among wootz blades and european blades from the same period.

I totally agree.

On the other side, it seems that there is another manuscript from Al Kindi dedicated to the thermal treatments of the blades made with wootz, which is not yet printed, though I understand maybe there is already an italian traslation.

I look forward to reading it.

I still believe the articles about viking swords refer to a relatively clean high carbon crucible steel, and not to wootz.

Allowing for some ambiguity, Wootz is crucible steel. See http://en.wikipedia.org/wiki/Crucible_steel

The swedish article mentions the presence of 0,8% refined carbon steel in one of the edges of the studied sword, and 0,4 to 0,6% carbon steel on the other edge. This opens the possibility of speculate about some specialization among the different edges of the viking swords, or at least in some of them, but it is only a good? pretext to continue our conversation.

Around 0.8% would have been optimal, but controlling carbon content is not easy - We must not forget that the ancient swordsmiths did not even know that steel was iron+carbon. Chance played a large part in the manufacture of ancient steel and this is why really good blades attained legendary status, in other words they were rare.

Some of the viking swords seem to be very complex in their structure, not because they are multilaminated in the japanese way, but because they have many different types of steels and irons in their composition, all welded in the make of the blade.

This kind of solution is not less sofisticated, or work intensive, than the japanese nihonto, in my opinion, but this is said with no regard of the differences on their success to have the best relation metallurgy-geometry-design, or to do with more effciency the expected job, as it is another very difficult subject to discuss with some scientific basis. Of course, this are only some of my ideas, and I can be wrong.

Well, my take on this is that a sword, indeed any weapon has to be only good enough to get the job done. Any more does not win wars.

Cheers
Chris

[Chris Evans]

Hi Jeff (D),

I have no first hand experience with Wootz, so I was hoping that Jeff Pringle or someone else would help us out. So what follows is really based on reading the works of others and reasoning back from firsts principles. If I am in error, others can correct me.

Originally Posted by Jeff D

Thank you Chris and Jeff.
Excellent explanation guys but, I think I may be missing something here. Is the central core wootz or crucible steel (on the real deals)? Just so that I am on the same page, my understanding is that wootz is crucible steel with a surface pattern, correct?

My understanding is that the term Wootz and crucible steel are synonymous because Wootz was made in crucibles, so it is a crucible steel.

Why would tempering crucible steel be any different then forged or case hardened steel? Tempering wootz would obviously be a much bigger problem if the surface pattern is to be maintained.

I am not sure that I understand your question, but if you mean why is the hardening of Wootz by a process of quenching problematic then this explanation may be of help:

The microstructure of forged Wootz, a very high carbon steel, in the unhardened condition consists of pearlite (0.8%C) plus the rest of the carbon in the form of iron carbides. In this state, Wootz can be hard enough to render a sword serviceable, but IMO barely so. To attain a really hard edge, hardening by quenching is required, but this is problematic.

Conventional hardened steel consist of converting the pearlite to austenite by heating and then this austenite is rapidly cooled (quenched) to transform it into martensite (hardened steel). If we only had pearlite to deal with, as in the case of conventional steels, there would be no great problem. However with Wootz, once the pearlite is heated and converts into austenite, the iron carbides tend to dissolve in it, raising its carbon content beyond 0.8% C. Upon quenching the austenite with the now elevated carbon content transforms into a very brittle form of martensite plus iron carbide that precipitates out of solid solution, all intermixed with some of the austenite that failed to transform (weak and soft), known as retained austenite. Whilst hard this is a bad microstructure from the point of view of strength and toughness. There is more to it, but this is a basic summary.

I have posted the picture of what I believe to be a temper line with an intact (but altered) surface pattern, to show that it could and was done.

One way around the above described problem would be to harden only the edge, so that the unhardened spine of the blade would provide the necessary strength and toughness that the blade requires. This would counter the negative traits of the hardened section.

In all my readings on Wootz, the question of heat treatment seems have received little attention, so we are left wondering. Yet to justify the legendary fame of many Wootz blades, they would have had to be hardened in some way or another.

Cheers
Chris

[Rick]

I own this old wootz sword .
http://www.oriental-arms.com/photos.php?id=1048

The pattern disappears where it seems to have been hardened (picture 2).

[Jeff Pringle]

a rough translation of that most interesting article, just to get the gist of it

My guesstimate is at the end of this post. The sword was made in a very similar way to the one analyzed by Edge & Williams, the main difference is the steel edge consisting of pearlite in the Swedish sword, not martensite. This might be due to a lack of hardening at time of manufacture, but it could also indicate that the sword went through a cremation burial which erased its heat treatment. Since the swords are so similar, I’ll presume they are both genuine +ULFBERHT+s and go with the latter.

could you shed some light on its historical heat treatment as uncovered by modern research, if such information exists?

This has always been a problem, not enough data on the old swords, but this recent article is a good start – Heat treated wootz/crucible steel has a significant edge over regular steel in hardness…
The Metallurgy of some indian swords
Alan Williams, David Edge
Gladius, Vol XXVII (2007):149-176
http://gladius.revistas.csic.es/inde...e/view/102/103

There is the theory that there was no need to harden wootz, since you just wanted very tough pearlite carrying those extra-hard carbides to the target, but since all the contemporary descriptions of wootz sword making include a quench, and since many swords look like they have a hardened edge, I suspect that theory is another modern misinterpretation based on too little info. Current experimentation reveals that water quenching is risky (well, we knew that already! ), that you can erase none, some or all of the pattern depending on the specific alloy and how you austenitize (heat before the quench) the blade, and that hardened and unhardened wootz respond to the etch differently, so yes, those weird lines that show up in the old swords & knives are evidence of heat treating. I’ll attach some fotos of quenched blades, from 1% to 1.9% Carbon. Lower carbon and the martensite grabs all the carbon, banding disappears, higher carbon and you get martensite studded with banded carbides. I recently bought an Indian wootz sword that was hardened at the edge in the area of the center of percussion, but don’t have a photograph of it (yet! )

Little different direction in this article

Better than the Guardian, but I suspect there’s still some misinterpretation going on. Yesterday I received a confirmation that the Williams article is on its way, so soon I’ll be able to compare all three!

wootz is crucible steel with a surface pattern, correct?

Wootz is hypereutectoid crucible steel with a pattern, you need to be over 0.8% Carbon to get the carbides.

The guts of the Swedish article:
Metallographic analysis of inlays in a Viking Sword, inv. nr. SHM 907
The blade is made up of several layers of varying carbon content, an almost carbon-free central layer with several weld joints marked by slag streaks, surrounded by two outer layers with higher carbon content. The central layer, which is built of 10-12 layers, consisting of relatively coarse-grained ferrite with small pearlite at grain boundaries, carbon content of less than 0.1%. The side layers are also layered and consist of one side of pure pearlite (carbon 0.8%) that is very fine-grained and finely laminated. The second side has lower carbon content, 0,4-0,6%; and consists of a powdery mixture of ferrite and perlite. The edge is badly corroded but seems to be the layer with the highest carbon content.
The inlay is almost entirely carbon-free, with coarse grains of ferrite. The cross-section is nearly trapezoidal and divided by a corrosion streak, which is probably a slag line between two twisted wires (Figure 3). The two threads show in their internal structure traces of stratification. The inlay is likely to consist of two twisted iron wires, probably containing phosphorous, which were forged down the fuller in the blade prior to the final processing to finished shape.

[Chris Evans]

Hi Jeff (Pringle),

Great post and many thanks for that most informative article in gladius, which I speed-read and yet have to go over several times so as to digest its contents. It would seem that the better blades were hardened by heat treatment.

Cheers
Chris

[kisak]

A thought about the heat treating of these hypereutectoid steels. As changing the carbon content in such would only change the amount of carbides, not the composition of the carbides and matrix (well, in theory at least), could it be that the smiths who were good enough with keeping the austenitisation temperature just so where then presented with a steel which might have been more predictable in how it reacted to the heat treatment?

Such could, I guess, result in a slightly higher overall quality amongst the blades which weren't more or less obviously botched.

[Chris Evans]

Hi Kisak,

Originally Posted by kisak

A thought about the heat treating of these hypereutectoid steels. As changing the carbon content in such would only change the amount of carbides, not the composition of the carbides and matrix (well, in theory at least), could it be that the smiths who were good enough with keeping the austenitisation temperature just so where then presented with a steel which might have been more predictable in how it reacted to the heat treatment?

Such could, I guess, result in a slightly higher overall quality amongst the blades which weren't more or less obviously botched.

From a modern perspective and without having done any hands on experimentation myself, it seems to me that Wootz is a variation on the theme of carbided tool steels, many of which have been adapted to cutlery usage. Their heat treatment is not difficult, but this is with modern technology, especially temperature control (pyrometry), all backed with knowledge. The general idea is to heat the steel just sufficiently to austenitize the pearlite and leave the primary carbides undissolved, so that upon quenching a sound microstructure results. With these tool steels the role of the carbides is to provide abrasion resistance. If you would like to read up on this here is a very good work: http://www.feine-klingen.de/PDFs/verhoeven.pdf

Whether any of the ancient smiths knew about this I cannot say, but do find it plausible that every once in a while someone would have got the temperature just right by chance with a very gratifying end result.

Again from a modern perspective, we would not make a sword blade from high carbon (hypereutectoid) steel because of lack of toughness, even if given optimal heat treatment. For one the martensite that forms at the higher carbon contents is very brittle and the cementite (iron carbide) does nothing, save to provide unnecessary abrasion resistance, and undermines toughness further. However in knives the added abrasion resistance is welcome and toughness is much less of a requirement.

Something to keep in mind is that piano wire, which is work hardened (hard drawn) unquenched pearlitic (eutectoid) steel is very tough, surprisingly hard and is used in springs. I mention this because of the possibility of cold work hardened but unquenched Wootz edges being up to the task of cutting very well and at the same time retaining a high level of toughness and springiness.

But there was more to ancient swordmaking than the above simplistic considerations would suggest. Those smiths could come up with composite layering and heat treatments and thereby overcome the inherent limitations of the steels that they worked with. How good were these swords? We don't know as there is not enough published data. Some time ago there was this thread http://www.vikingsword.com/vb/showthread.php?t=3377 and the question posed in the first post remained unanswered.

Cheers
Chris

[Chris Evans]

Hi Folks,

Here is something I posted on that earlier thread on Wootz and may be of general interest:

By Dr. John Verhoeven:

There is a general myth in some of the popular literature that genuine Damascus steel blades possess outstanding mechanical properties, often thought superior to modern steels. This idea was shown to be incorrect as long ago as 1924. A famous Swiss collector, Henri Moser, donated 4 genuine Damascus steel swords, one with a non typical carbon content and microstructure, to B. Zschokke, who performed extensive careful experiments including metallographic and chemical analysis in addition to mechanical testing [15]. A series of bending tests compared samples from the swords to a pattern welded blade and a cast blade from the famous German knife center in Solingen. The 3 good Damascus blades showed significantly inferior bending deflection prior to breakage than the 2 Solingen blades in spite of the fact that the Brinell hardness of the 3 ranged from only 193 to 248, compared to 347 and 463 for the pattern welded and cast Solingen blade, respectively. This is not too surprising in view of the now well known fact that toughness of high carbon steels is inherently low; the Solingen blades had carbon levels of 0.5 to 0.6% compared to 1.3 to 1.9% for the 3 Damascus blades. The reputation of Damascus steel blades being superior to European blades was probably established prior to the 17th century when European blades were still being made by forge welding of carburized iron. It is hard to avoid embrittlement of such blades due to imperfect welding during the forging process as well as difficulty with the carburizing process.

The full article is here: http://bronksknifeworks.com/historical.htm

Cheers
Chris

[Gonzalo G]

Hi Chris. Now I understand what do you mean with "sponge iron". We have modern processes to make sponge iron which are something diffrerent, and from it came my confussion. About the crucible steel: yes, the term has been used as synonymus, but there are crucible steels not being wootz, and also mentioned by Al-Kindi as not being "watered". I don´t think this term do not refers necessarily to a specific type of steel, but to to a specific method of production. Anyway, I don´t intend otherwise but clarify for myself what did you mean, and this is done already. Thank you, Chris.

About this comparison among wootz and modern steels, I agree that most probably modern steels are superior, but neverthless I find those experiments biased, as the blades selected are not representative (statistically or otherwise) of the best wootz blades made in older times. To begin with, we don´t know what quality standards were used to make the selected blades. In nihonto, you can find a wide variation of quality among different blades, depending if they were made, or not, by "masive" production for poor samurai, or the particular bladesmith who made the blade. On the other side, I think the comparison must be made among blades from the same historic timeline, so we can state if the metallurgy and craftsmanship of one area was superior to the one of another area. Otherwise, this comparisons tend to diminish the value the wootz had in their time and drive to false conclusions realtive to the technology and craftsmanship level of other peoples.

I agree that wootz was not a magical steel. And also, I believe that is a steel not scientifically well known to make a definitive evaluation, though it´s beauty is unquestioned. Most of the today´s statements made about the value of this steel, are only presumptions.
Regards

Gonzalo

[Chris Evans]

Hi Gonzalo,

Originally Posted by Gonzalo G

About the crucible steel: yes, the term has been used as synonymus, but there are crucible steels not being wootz, and also mentioned by Al-Kindi as not being "watered". I don´t think this term do not refers necessarily to a specific type of steel, but to to a specific method of production.

From S. Srinivasan and S. Ranganathan Department of Metallurgy, Indian Institute of Science, Bangalore:

Wootz is the anglicized version of ukku in the languages of the states of Karnataka, and Andhra Pradesh, a term denoting steel.

http://materials.iisc.ernet.in/~woot...e/Heritage.htm


Where do we go from here? I suppose that one immediate way of addressing the problem of ambiguity is to state what one means by Wootz, whenever using this term.

About this comparison among wootz and modern steels, I agree that most probably modern steels are superior, but neverthless I find those experiments biased, as the blades selected are not representative (statistically or otherwise) of the best wootz blades made in older times. To begin with, we don´t know what quality standards were used to make the selected blades. In nihonto, you can find a wide variation of quality among different blades, depending if they were made, or not, by "masive" production for poor samurai, or the particular bladesmith who made the blade. On the other side, I think the comparison must be made among blades from the same historic timeline, so we can state if the metallurgy and craftsmanship of one area was superior to the one of another area. Otherwise, this comparisons tend to diminish the value the wootz had in their time and drive to false conclusions realtive to the technology and craftsmanship level of other peoples.

Comparisons like these tend to be both invidious and odious - Nevertheless to gain an overview and basic undertsanding of what we are dealing with they have to be made, especially if we wish to appraise its contextual historical worth. To people who are not metallurgists, Wootz may as well be Kryptonite, given the legendary status it enjoys. Same for the Japanese sword.

I agree that wootz was not a magical steel. And also, I believe that is a steel not scientifically well known to make a definitive evaluation, though it´s beauty is unquestioned. Most of the today´s statements made about the value of this steel, are only presumptions.

The appraisal of the steel is one thing and that of swords made from it quite another. When it comes to the swords, I fear that we'll probably never know their true capabilities because it would be tantamount to vandalism to subject the best surviving specimens to testing that would necessarily be destructive. As for the steel, well, at least from a metallurgical point of view we do know that it is a bit of a mixed bag. My personal feeling is to agree with Verhoeven.

Cheers
Chris