True Combat Value of Wootz

[Ian]

Chris:

It's unclear to me what properties carbon nanotubes and nanowires might convey to steel. The authors suggest that such structures might explain the extaordinary cutting properties and strength of wootz versus other steels. Since we are having trouble here agreeing that wootz per se did have such special properties, I would put the discovery of these microstructures in wootz as interesting observations deserving further attention, but far from conclusive evidence that they convey special properties to wootz and not other steels. Do we know that these nanotubes and nanowires do not occur in other types of steel? Do we know that such strcutures convey greater strength and sharper cutting edge?

I suspect that wootz is not unique in regard to having these structures. Perhaps Dr Ann can help us here.

The article abstract is here: http://www.nature.com/nature/journal...s/444286a.html

You can purchase the full article online for $30 (I recommend the PDF version) here: http://www.nature.com/nature/journal...l/444286a.html. Or you can go to your local library, get the November 16, 2006 number of Nature, p. 286, and photocopy the article for pennies.

Ian.

[Chris Evans]

Hi Ian,

Originally Posted by Ian

Chris:

It's unclear to me what properties carbon nanotubes and nanowires might convey to steel. .

I learned and practiced my metallurgy before the advent of so called nano-technology, so I confess absolute and total ignorance about the effects of sub microscopic structural components on the mechanical properties of steels, indeed any material. At this stage, all I can do is apply some basic logic to evaluate the evidence presented. But first I must read the full paper.

The authors suggest that such structures might explain the extaordinary cutting properties and strength of wootz versus other steels. Since we are having trouble here agreeing that wootz per se did have such special properties, I would put the discovery of these microstructures in wootz as interesting observations deserving further attention, but far from conclusive evidence that they convey special properties to wootz and not other steels. .

I thinks that we can safely accept that Wootz was, if properly forged and heat treated, at least potentially a notch above other contemporary steels. GT Obach's experience is agood example, and even 50yrs ago it was talked about (by metallurgists) as an outstanding early steel.

However, you raise the same points that I immediately thought of, namely that the same sub-microscopy structures may be found in other steels and may not be exclusive to Wootz.

Additionally, I have yet to see (it may have been published but I haven't seen it) comprehensive mechanical test results of Wootz vs more primitive steels, not to mention an exhaustive analysis of the mechanical loads that a sword edge is expected to cope with. Hardness I have seen, but not the other properties - We need this data before we can make valid comparisons. If it turns out that Wootz did indeed have superiors mechanical qualities over good quality primitive steel, then we can start exploring the contribution, if any, of its sub-microscopic structure.

Cheers
Chris

[Ann Feuerbach]

Hi all,
Just got back from a conference and will be reading the nature article soon. I have seen some work on nano structure in a 2004 article. History section in all these areas are bad. FYI wootz, only from 1795, not a real word, too bad it is used so much as it is so inaccurate and as no etymological roots.

[Andrew]

Originally Posted by Ann Feuerbach

Hi all,
Just got back from a conference and will be reading the nature article soon. I have seen some work on nano structure in a 2004 article. History section in all these areas are bad. FYI wootz, only from 1795, not a real word, too bad it is used so much as it is so inaccurate and as no etymological roots.

Hi Ann. Welcome back.

So, it sounds like the much more accurate term would simply be "crucible steel"? How about the term "balut"?

[Ian]

Originally Posted by Ann Feuerbach

Hi all,
Just got back from a conference and will be reading the nature article soon. I have seen some work on nano structure in a 2004 article. History section in all these areas are bad. FYI wootz, only from 1795, not a real word, too bad it is used so much as it is so inaccurate and as no etymological roots.

Thanks Ann.

Hope the conference was enjoyable, informative and productive. Like Andrew, I would welcome your suggestion for a better term than wootz. Look forward to hearing your views about the possible significance of these fine sub-micronic structures that have been described recently.

Regards,

Ian.

[Ann Feuerbach]

Hi all,
Bulat is good, but pulad (phulad) is better, because bulat comes from pulad or a related term and variations of the word pulad can be found in many languages. I did an etymological study of the words. The earliest use of the term pulad is a 6th century AD text. It may have originally came from Sanskrit or Avesten (which had a common root language). In sanskrit languages the prefix pu means pure or purify, while there are hundreds of words for iron in the languages of India including loha, lauha, etc. Pu loha (meaning pure or purified iron) or such was probably the origin for the word. I have checked this theory out with Sanskrit scholars and they agree with this.

I have no problem with the use of the term wootz when refering specifially to Indian steel, but the word assumes a geographic location, which can be inaccurate and assuming. I prefer the term crucible Damascus steel to prevent assumptions.

On a related note: If I read one more reference in the news, including the Nature article and National Geographic news (where the author even contacted me but took no notice to what I said) to the process being only from India, being lost, and references to crusaders and Damascus, Syria I am going to scream!

[Rivkin]

I think what we have here is a cultural issue. I grew up in a commpunity (Asia/Eastern Europe) where "bulat" novadays simply means steel. Any steel. Even if you buy almost any translational of any old text, you will see that translator uses word "bulat" with no regard for the original text, i.e. assumes that it simply means steel. This is why you occasionally see russian works on bulat that pronounce that you know what (since we don't know how to call it ?), was used by Roland, prince Igor and virtually every other historic person, because the author did not check the manuscript's original for the exact _original_ wording.

Even in XIXth century, per Anosov, bulat meant any steel with a pattern, whether it is mechanical, you know what, or something even more simple.

The "wootz" word for me is a slang and I think we need such a word to clearly identify what we are talking about.

[Chris Evans]

Hi Folks,

Rivkin very kindly sent me a copy of that paper that was published in Nature. He is indeed a gentleman and a scholar and my sincerest thanks go to him

I hurriedly read it and the thing that immediately struck me is is the claim that Wootz had superior qualities, without telling us which exact attributes were being talked about. After all, in the context of swords, there are a number of mechanical properties that are considered desirable, most having to do with hardness and toughness. Hardness, is relatively simple, but toughness has many aspects.

The most often mentioned advantage of Wootz is its supposed combination of hardness and ductility resulting from the presence of carbides and nearly pure iron in its microstructure. The simplistic logic appears to be that the hard carbides do the cutting and the soft near pure iron provides the toughness. This paradigm is contrasted by that of conventional quenched & tempered Martensitic steels in which the same homogenous microstructure embodies both attributes.

Whilst true to some extent, I have a lot of trouble in accepting the above line of reasoning as a justification for declaring Wootz to be a superior steel. After all, it is well known that steel obtains its optimal hardness and toughness in the quenched and tempered Martensitic state, though I hasten to add, that work hardened Pearlitic steels, such as piano wire, can also be both surprisingly tough and hard. Whether Wotz swords were ever work hardened to to the same extent as modern piano wire, I have yet to find out.

A theoretical evaluation, from first principles, of Wootz is very difficult because the very large number of variables to be considered and all this has to be done in the context of various sword, the design of which introduces yet more variables.

Based on the papers that I read, most Wootz blades were not Martensic, rather work hardened Pearlitic with additional iron carbide embedded in it, though GT Obach did make the very important observation that partially quenched Martensitic blades, where the edge was expected to do the cutting, as well as fully quenched, were not uncommon. However, here we have to remember that once the carbon content of Martensitic steels exceeds 0.8%, the surplus carbon precipitates out as iron carbide, which can have detrimental effects on toughness, depending on its microstructure and localization. Whilst this effect can be minimized with very careful heat treatment, it is extremely unlikely that the ancients would have had the means or knowledge to achieve this.

So where does this leave us in relation to carbon nanotubes and which properties did these influence? I am at a loss.

Just looking at the evidence that so far I have managed to lay my hands on, it would appear that in centuries past Wootz acquired its formidable reputation more than anything else on account of the fact that it was melted during firing.

Unlike primitive steel, Wootz was free from insoluble inclusions, such as slag, which would float to the surface -The presence of coarse lumps of impurities in primitive steel could greatly weaken it and hence the need to remove these and disperse uniformly what remained - This was done by the process of extensive hammering and folding. But the presence of these impurities could only be minimized, never eliminated, and as such, primitive Martensitic steel always had a question mark against it. Also, during the process of hammering and folding, often the welds were incomplete due to poor technique or bad luck, introducing additional flaws.

To complete this rambling, I should reiterate that the great disadvantage of primitive Martensitic steel, in contrast to Wootz, was its variability due to the then poor understanding of metallurgy, as well as the presence of slag like impurities.

Of course, Wootz was good steel to start out with, but the forging process could very easily ruin it and the end product was not necessarily any better than that made from primitive steel. I think, that by sheer chance, it was possible to make a sword out of primitive Martensitic steel that was every bit as good as those made from Wootz, for in the end, all that was required was a correctly heat treated blade of about 0.8% carbon (optimal) and largely free from slag inclusions; But given the then extant incomplete knowledge of metallurgy and on the balance of probabilities, the odds lay with Wootz to deliver a superior blade.


Cheers
Chris