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Ancient Swords Made of Carbon Nanotubes
brian0918 writes "Nature reports that researchers at Dresden University believe that sabres from Damascus dating back to 900 AD were formed with help from carbon nanotubes. From the article: 'Sabres from Damascus are made from a type of steel called wootz. But the secret of the swords' manufacture was lost in the eighteenth century.' At high temperatures, impurities in the metal 'could have catalyzed the growth of nanotubes from carbon in the burning wood and leaves used to make the wootz, Paufler suggests. These tubes could then have filled with cementite to produce the wires in the patterned blades, he says.'"
So swords are a series of tubes too?
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If you think big enough, you'll never have to do it.
But I didn't know it was called "wootz". That's almost too good to be true. Next we'll find out the it's made of pwned ore.
Am I part of the core demographic for Swedish Fish?
This, for instance, tells the story of old Damascan warriors that would run around slaying their enemies, and at each kill would shout a prayer of "W00Tz" to their ancient sword gods to thank them for their glorious victory.
Since the secret of manufacturing was lost in the 18th century, it would make sense that they were still made during 1500-1600. How would their properties in manufacturing compare to the folding method of the Japanese katana? Would the nanotubes be present in the katana as well, or was this unique to Damascus?
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"Pwning ore sire!"
Would you kindly mod me +1 insightful?
Maybe I'm mis-reading your post, but it sounds like you're thinking of pattern welding. The true damascus steel was produced in a different way from pattern welding. Because the of the similar appearance of the two steels, pattern welded blades are just called damascus steel nowadays.
Scientific American reported over a year ago that a metallurgist and a blacksmith managed to reproduce Damascus steel. The secret was in the Wootz. Wootz is a lump of iron that was produced at the mine, then exported. The folks in India didn't know how to make it into Damascus steel, the folks in Damascus did, but the process only worked with a wootz from one particular mine in India. The mine in India played out several hundred years ago. That's why the secret died, after being a state secret for over 1000 years. It stopped working.
According to the team SA reported on, the secret is in a small amount of molybdenum. the process of manufacture used up to 50 forgings, and used acids to etch designs into the blade. The forgings cause microscopically fine strands of molybdenum to be located throughout the steel, breaking up the crystaline structure, and with it the fracture points. This also caused the famous 'watermarks' that all true Damascus steel has.
As some nanotubes result from almost any coking process, there would be nanotubes in there, (vanishingly small quantities), but the strength would come from other things.
I understand that it is now possible to buy a new Damascus steel sword again, but the price is very high. (it always was.) A flying car might be cheaper.
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Almost every post on slashdot has an overlord joke with a +5 Funny rating. I'm waiting for the day when its not funny any more...
I, for one, do not welcome our eventual humorless overlords.
simple - the slashdot mod system is broken, funny posts get no positive karma. Thus, kind moderators will often mod a funny post as informative or insightful, so that the poster gets the karma.
this can really fuck you over, by the way, if you tell a controversial joke... get modded +5 funny, then get a -1, troll, and another funny, and another troll. When a moderation war kicks in, you keep losing karma from the -1 troll's and gain no positive karma from the +1 funny's. Eventually you could end up with a +5 post that cost you an assload of karma.
I'm waiting for the day when its not funny any more...
You missed it already. See, it gets not-funny after awhile, and then using it becomes the joke itself and so it is made funny again, only to eventually be over-used and become not funny again. Repeat until the sun goes nova.
You're a bit confused here. First off, Damascus steel can refer to two types of metal: pattern-welded and wootz. The folded type is pattern-welded; any asshole can make this. You just take a couple of different ores, fold them together a few times and you end up with patterns. The acid or laser or whatever bath is simply used to make the finished sword look better. It doesn't really change the chemical or mechanical makeup of the sword (ie dunking Herbert Q. Orcslayer in acid will never turn it into Damascus).
Wootz is an entirely different animal. The technique was lost because it depended upon certain ores with trace impurities which dried up in the 1700s or so. The carbon would clump together which formed the distinctive banding.
Summary: pattern-welded = 2 different ores folded in alternating layers form a pattern, wootz = forging process and chemical composition of ore results in macroscopic pattern-forming carbon lamellae
Just an aside, as someone with a little history in metallurgy:
Pattern-Welded is actually a weaker sum of the metals that went into it's production. Molecular cohesion just does not happen, the metals aren't being smelted or wrought together in a way that is conducive to improving the strength of iron. No matter if it's 2 steels being sandwiched (which is basically the process used when going for aesthetics alone) or even if it's a tool steel being etched by laser or in an acid bath; which is also done.
Damascene steel on the other hand, is extremely strong. It can hold an edge while still maintaining flexibility. The silica content as well as the amount of tungsten present in the sand from which the iron was extracted is a synergistic combination. Silica providing flexibility (I'm hacking a metallurgical textbook in half to get where I'm going, forgive me), with the tungsten giving the steel a little UMMF that none other had at the time--bands of tungsten carbide. In itself completely inflexible but present as it is in most blades it actually is given alot of room to move.....by the silica.
Similar qualities are present in the tungsten rich sands of some Japanese waters. However not in the same manner, the Japanese had an ingenious forging method, sometimes referred to as the 1000-leaf method by those speaking of it in English.
REAL Damascus steel is still legendary not only among sword and knive enthusiasts, but amont metallurgists as well. It is for all intensive purposes a wonder-metal, even by today's standards. In today's day of Titanium, Monel, Inconel and Carpenter-20, Damascus is still something people in the field whistle about.
Of all the Universal Constants, here's one I know: Nice guys finish last
While later Japanese swords were made by forging different metals together, very early swords were not--they were forged from a solid piece of steel. The steel was beaten flat and folded over itself several times, but it was not to impart mechanical qualities--it was to mix the carbon evenly throughout the impure metal. (Later this was accomplished through better steel manufacturing, so the folding was replaced by the multi-part welding of of different alloys as described.)
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Once the sword was shaped it was quenched. However since they wanted different properties on the edge vs. the spine, they needed to cool the different parts at different rates. This was accomplished by painting the sword with varying thicknesses of clay--thick on the back for a slow quench (resulting in soft but springy steel) and thin on the edge for a fast quench (resulting in hard but brittle martensite). This differential cooling also caused some of the curvature. It also allowed a sword maker to impart a "signature" of sorts, by painting patterns into the clay. This manifests itself in the subtle wavy reflective pattern seen along the cutting edge of many katanas, called the hamon.
Finally to address the GP, the original pattern that is now called Damascus had nothing to do with folding the blade. If you look at an original Damascus blade the pattern is not alligned to the edge but runs throughout the blade. It has more to do with the steel composition and how it was forged.
Sources for more info:
http://en.wikipedia.org/w/index.php?title=Katana&
http://www.mines.edu/Academic/met/pe/faculty/ eberhart/classes/down_loads/damascus.pdf (PDF)
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An ideal sword would be both flexible and sharp, and a number of cultures have achieved this goal via pattern welding (welding alternating thin layers of hard and soft steel), most famously the Japanese katana, but this technology was well known in the ancient world, and is evident in recovered Viking swords, Indonesian kris, and as far back as Roman times (for use in decorative steel artifacts). Its use can also be found in a few modern knives (see Swedish Mora).
This differs from the damascus technique, which was rediscovered in the 1980's by Alfred Pendray and John Verhoeven. They didn't mention nanotubes, just the necessity of small Vanadium impurities in the ore. This explains the 'lost technology' of damascus steel very well, ie. when the original ore deposits containing said impurities were exhausted, the technique simply did not work anymore.
In fact, your explanation of the process is a tad wrong... here comes an explanation closer to reality
For simple carbon steels, beating the shit out of the edge just gives it its basic shape (it will be refined later at the polish stage). The formation of bainite, martensite and pearlite is caused by the cooling rate. Thus they come from the quenching and subsequent tempering of the blade. The tempering is mainly there to relieve the internal stresses caused by the structure reorganisation triggerred by the quench (and reduce the hardness by a few Rockwell points). Basically (very simplified), a fast cooling rate will give you pearlite while a slower cooling rate will give you martensite and if you keep it a long time at the correct temperature, you'll end up with bainite.
A prime example of that concept is the way japanese swords are made (oversimplified once more, as this is not a smithing forum).
After you've given a basic edge shape to the blade, you apply clay on the edge (and a bit on the spine, too) then you bring the whole blade to non-magnetic temperature and you quench it. Three things can happen at that point:
- the blade curves towards the back (due to the different cooling rates) and the crystalline structure changes (martensite and friends under the clay, pearlite where there is no clay)
- the blade curves towards the edge (can happen with 5160 quenched in oil), it's a miss
- the blade cracks due to the stress (you used the wrong quenching medium for your alloy or heated the blade too much)
If the blade survived, you can then temper it by bringing it back to a certain temperature (depending on the alloy) so the internal stresses are relieved and the surface crystalline structure can change a bit too (if the temp is in the correct range). After that, the smith gives the a very rough polish before sending it to a real polisher.I do agree about the L6 bainite swords by HC, they are amazing ;) L6 in itself is just a tooling alloy (used for saw blades, IIRC), the properties of the L6 swords come from the controlled temperatures of the salt baths used by Howard. He is keeping the blades at a very precise temperature range for a certain amount of time to maximise the reorganisation of the crystalline structure to bainite. I don't haved the temperature graphs for various structures handy, but they're quite easy to find on the web ;)