Damascus steel
The term Damascus steel (also: Damascus steel and Damast), derived from Damascus ( Arabic دمشق Dimaschq ), denotes a material made of one or more types of iron / steel , which in a polished or etched state reveals a clear structure made up of several alternating layers of different raw materials.
Today the term Damascus steel primarily describes welded composite steel, which has been produced in Europe for more than 2000 years. This steel is popular again because of its decorative pattern.
The crucible steel ( Wootz ) imported into Europe via Damascus and manufactured in the Indo-Persian region until the beginning of the 18th century was originally called Damascus steel. The exact manufacturing process is not known. This steel also has a pattern that can be made visible by etching. However, it is not as pronounced as with composite steel.
The welding damascus steel
The starting material is iron or steel
Steel is an alloy of iron with other elements, mainly carbon , which is not uniformly defined. According to DIN EN 10020: 2000–07, the carbon content of the iron must not exceed 2.06% by weight, otherwise it is cast iron . A distinction between iron and steel is not possible in connection with old manufacturing processes, since solid (chemically pure) iron hardly occurs in nature. Blade-compatible steel is characterized by a carbon content of around 0.5 to 1.2% and should be highly pure and easy to weld and forge .
The starting material for the production of modern Damascus steel are steels with different contents of accompanying elements. The most important accompanying elements that determine the properties are carbon, manganese, silicon and nickel. Steels with defined chemical compositions could not be produced in a targeted manner until modern times.
The only method of producing iron up until the late Middle Ages was to smelt iron ore in a racing furnace . The product of this process is what is known as a sponge iron , also known as a luppe . Since the billet shows a very differently distributed carbon content and slag inclusions, the material first had to be homogenized and forged into a usable ingot, which was achieved by multiple forging, folding and fire welding. The process is called refining or fermentation. Only such a homogenized material has predictable, uniform properties. Using certain techniques (freshening, cementing), a targeted reduction or increase in the carbon content could be achieved. Together with the knowledge of the correct heat treatment of the material, the technical properties could be determined very precisely.
Differences between refined steel and welded damascus steel
The transitions from refined steel to Damascus steel are fluid. Both terms are welded composite steel .
Refined steel is created during the production of the raw material when no liquid iron is available as a base. This is the case with racing kiln production. The aim of the refining process is to homogenize the shell into a material with the same composition throughout. Refining is thus part of the raw material manufacturing process.
Damascus steel is the deliberate combination of different raw materials in order to guarantee certain properties in the product. In the beginning it was not about the creation of patterns, but only about homogenization. The Viking Damascus steel was a combination of different types of iron, one of which contained phosphorus, which turned out to be metallic-silvery in the final etching treatment, while other components were rather dark. This finally made it possible to produce a sample.
The welding of identical iron / steel types and iron scrap (OROSHIGANE) for the production of a blade, as is done by Japanese swordsmiths, does not lead to a clear welding pattern (= damask). This is only about homogenizing and setting certain properties.
Welded composite steel is the definition of refined steel, which is composed of several pieces of different raw materials by means of fire welding. Analysis of some archaeological finds is difficult.
Modern steel, obtained in liquid form, is not refined steel. Refining is not necessary, as the liquid form ensures sufficient mixing of the elements. Damascus steel can be made from modern steels as long as they can be hot-welded.
Requirements for weapon steel
Problems in the manufacture of edged weapons , such as swords, arise from the properties of the hardened steel . Because of its intended use, a sword must withstand high shock loads, must remain sharp and must neither break nor bend.
With the help of heat treatment (hardening and tempering) steels can be given different properties. In this way, blades can be produced that remain sharp for a long time and do not bend, but are brittle and break relatively easily. Likewise, the blade steel can be given more toughness by means of suitable heat treatment with a slightly lower hardness. In this way, blades can be produced that do not break easily, but also do not stay sharp as long. The myth of "hard" and "soft" layers in Damascus steel, however, was not the solution for the early medieval swordsmiths, because they only used their damask - mostly for decorative reasons - in the blade body and not in the edge of a blade.
Hardenability
One of the most important properties of steel that makes it superior to bronze is its hardenability . Steel is hardened by cooling glowing workpieces as quickly as possible. This can be done in cold water or oil, for example. Since when this hardening process has been consciously and specifically used is not exactly traceable, but was probably already known to the late Celts. It can be assumed that this effect was noticed early on, as certain desired combinations of different raw materials only made sense with a later hardening. Basically, steel can be brought to its full hardness of 62 to 67 HRC . Since the hardening (depth effect of hardening in the material) is limited to approx. 4 mm in low-alloy carbon steels, tools and blades could be fully hardened due to their small material cross-sections. There are archaeological finds from Roman times in which the blades had degrees of hardness over 66 HRC.
During hardening, microcrystalline structures of the carbon compounds form in the metal lattice, which are extremely strong and hard. Only iron with a carbon content of more than 0.22% can be hardened. As the carbon content increases, the degree of hardness increases. The steel becomes more brittle, stronger and less subject to wear. However, it is not just the carbon content that determines the mechanical properties of the steel. Other alloying elements such as phosphorus (steel pest, makes iron brittle), manganese (makes iron tough, improves hardenability) or silicon (also makes iron tough) play a role.
History and Development
One theory about the development of Damascus steel in Europe is that it was an attempt to copy oriental art. The assumption cannot be confirmed in this way, as blades made of Damascus steel have been found in Europe since the pre-Roman Iron Age , while oriental crucible steel was only known from the 17th century. Only the term is taken from the name of the oriental steel. It can be assumed that in earlier times steel had no name of its own and fell under the term fermentation steel. The oldest evidence of intentional Damascus steel so far are Celtic swords made of striped Damascus steel from around 300 BC. Chr.
For the forging of antiquity it was first important that the racing furnace process generated Renneisen (also Luppe called) was even malleable. The blacksmiths of that time could only approximately assess the carbon content, remove slag from the metal and bring about a certain homogenization of the iron. Due to the complex process of iron ore smelting, the production of raw materials was separated early on, so that forges iron bars of various qualities were available as commodities. Investigations on early blades show that relatively pure steel was used, especially in the cutting area.
One reason for the development of Damascus steel in antiquity and in the early Middle Ages was that the steels obtained using the racing kiln process were not always of the same quality because the smelting process could not produce standardized steels. Additions such as carbon, phosphorus and sulfur influenced the quality and often required reworking for the targeted control of the properties of the finished product. The blacksmiths were thus able to select the various qualities specifically for the manufacture of certain products such as swords or horseshoes.
Perhaps over time it was recognized that blades made from different steels were more efficient. Iron blades with a steel insert in the cutting edge were more stable than those made from a single piece of iron. The different carbon contents and the heat treatment were responsible for this. Recycling was already being practiced in the forge, because steel made from old tools was found in antique and medieval weapons and tools. Already in the Hallstatt period , swords made of different refined steel were found, which after etching resemble the so-called wild damask . In this case, no intended or regular structure can be identified.
Damascus steel structures can be recognized in some cases from finds in the ground, as the different layers of the steel corrode at different rates. This reveals the structure of the steel. A corroded excavation that reveals different layers of steel is not necessarily made of Damascus steel; corroded refining steel / fermentation steel also shows layer-like structures. Badly refined steel usually shows clearer structures than finely refined steel.
The Celts brought iron to the market in the form of pointed bars, the thin forged ends of which could be broken or bent to check the quality of the material, thus allowing conclusions to be drawn about the purity and ductility of the material. Such bars were often traded over long distances and were in circulation in standard sizes, weighing up to 11 kg. For a sword a lot of raw material with a certain amount of carbon was needed to give the blade hardness. This led to a specialization in the blacksmithing profession early on. Since the bars sometimes came from different smelting areas, they could contain various impurities and accompanying elements, mainly carbon and phosphorus.
This development reached its first high point in the Latène period with the bulbous pommel swords of the Celts , which were probably made deliberately from welded composite steel. However , it is not known whether the beginnings of the use of welded composite steel can be found in the culture of the Celts. It is possible that the technology was adopted by other peoples, such as the Scythians .
In Roman reports, however, the swords of the Celts were portrayed as poor quality. In a Roman tradition it says: "The Celtic warriors often had to withdraw from the fray behind their ranks to straighten their swords with their feet". However, this does not have to mean a contradiction: it is conceivable that it was simply impossible to equip an entire army with weapons of the highest quality. A warrior's social position and financial resources may have had an impact on his equipment. In this context, it is necessary to differentiate between different Celtic tribes. The Celts consisted of many individual tribes that were often at war with one another. Differences in blacksmithing between the tribes would therefore not be surprising. For example, the Celtic tribe of the Noriker were famous for their forged goods, especially their swords, and were to a certain extent "home suppliers" to the rich Romans. The Roman reports about the bad swords of the Celtic Gauls (see e.g. Gallic War ) can also be propaganda.
Welded composite steel was also used in the Roman Empire , but finds from this period are rare.
The Germans created at the time of migration of peoples excellent weapon with highly ornate Damascus steel works that were also differentially hardened (worm colorful 'blades). For the first time, not only functionality was in the foreground, but artistic implementation - with an artistic blade promising high functionality. Many swords bore names and were almost cult objects.
Germanic sax blades and late Roman swords have been found that are equivalent to Japanese samurai swords in terms of hardening. This was discovered by treating selected blades according to traditional Japanese polishing and thus gaining knowledge about their manufacture and internal structure.
In the course of time, the blacksmiths learned to control the folding and torsion processes in such a way that they could specifically produce certain patterns. This is best known from the Vikings and Franks.
From the late Middle Ages , there were blast furnaces that could liquefy iron and produce high-quality, malleable pig iron . The existing processes of ferrous iron production and the associated refining were replaced. As a result, the complex process of producing Damascus steel lost its importance. Not until the late 17th century. This found increased use again, primarily for the barrels of firearms.
With the availability of good, cheap steel at the time of the industrial revolution , Damascus steel finally lost its importance.
Preparation of the source material and background
The iron ore (often turf iron stone), which was piled up alternately with charcoal in the kiln , was brought to high temperatures (around 1250 ° C), causing the stone to melt and run off as slag . The iron oxide contained was reduced to iron by the reaction gases in the furnace in the solid phase, which at the end of the process was present as a lump at the bottom of the racing furnace. The porous sponge iron was interspersed with slag and carbon residues and had different carbon contents depending on the position in the furnace. The process is called direct reduction.
In order to get usable material, the shell had to be cleaned (refined) through further processing in special refining ovens or in the forge and converted into the form of a semi-finished product. Another necessary process step that is crucial for this type of steel production!
The aim of the refining process is to drive off the impurities and to transform the sponge iron into a compact, homogeneous material. Refining essentially consisted of the continuous repetition of fire welds between the material and itself. The hollow spaces in the shell were closed, the impurities were largely expelled and the remainder was very finely distributed in the material. This step can be seen as a crucial key technology for the manufacture of early iron products and welded damascus steel.
An even more technically important step in iron production is refining. The aim of freshening is to reduce the carbon content to the level required for the end product. This process takes place during iron making in the forge fire.
“Carburizing” - known as cementing - was known very early on. This is a process that aims to increase the carbon content in iron. It was used to produce hardenable steel.
With the knowledge of these three techniques, the setting of the carbon content and thus at the same time the setting of the basic properties of the steel was mastered. By using the appropriate method in the heat treatment, these properties such as hard, tough, soft, brittle, wear-resistant, elastic, etc., related to the desired purpose, could be highlighted and specifically created.
Welding damascus steel manufacturing process
Damascus steel that is not industrially produced is still manufactured today in a similar way to earlier, but supported by technical innovations. The process is similar to the process of refining steel using fire welding.
At the beginning, several (usually 3 to 15) layers (usually two or three) of different starting materials are alternately placed on top of each other and fixed (occasionally by electric welding , if you want to safely exclude shifting of the layers). The resulting block is then heated and fire-welded. The composite is then separated lengthways or crossways, placed on top of one another and welded again (folds). The procedure is repeated several times , similar to the production of puff pastry .
Glowing sheet metal package with melting borax
Forging with a monkey
Forging with a monkey
End product: multilayer Damascus steel
Different steels are used for modern Damascus steel such as
| European steels: | |
| ck45 | simple carbon steel with good toughness |
| C60 | Carbon steel, tough, easily hardenable |
| C105W1 | Carbon steel of the highest quality and hardness for high-performance damascene steels and as a starting material for refining steels. |
| 16MnCr5 | Case-hardening steel. Difficult to weld due to chromium content, but very good to draw with. |
| 90MnCrV8 | Tool steel. The classic "damask maker" has largely displaced the C 105 W1 from the German market. Dark drawing due to manganese content, high hardness. |
| 1.2008 and 1.2063 | Tool steels mainly used for files. Hardness up to 67 HRC. |
| Japanese steels: | |
| San-Mai: | Term for three-layer steel |
Since the number of layers doubles after each laying on top of one another, hundreds of layers are present after a few repetitions. The main difficulty with fire welding is that the material must not exceed a certain temperature , otherwise the carbon will burn. At the same time, the material must not scale (oxidize) too much, because then it can no longer be forged together. Since the steel starts to burn before the melting point ( oxidation ), borax is scattered as a flux on the area to be welded towards the end of the heating process . This melts into a liquid glass layer and thus protects the steel from the ingress of oxygen. The right time for this is (depending on the material) when the first stars ( sparks ) of the burning carbon appear. A glassy shield is created that encloses the two parts to be welded. This not only serves as protection against the ingress of oxygen, but also as a solvent for the oxides that form on the glowing surface. In this process, it is important to have a quick, decisive treatment on the anvil , which is acquired through practice.
In order to obtain patterns on the surface, the steel can be twisted ( torsion Damascus steel ) or further processed "asymmetrically" ( wild Damascus steel ). Nowadays, after hardening and fine grinding / polishing, the Damascus steel is etched to make the pattern visible. The different layers are attacked to different degrees by acid treatment and thus create a pattern on the surface of the blade. In earlier times, blades were very finely polished, which offers a certain degree of protection against corrosion and can also make the different layer sequences clearly visible. This technique was refined on Japanese blades and is still used today. The significantly finer structure of the homogeneous steel, which was created by refining, counts as a quality feature here. This cannot be made visible by etching.
With knives made of simple Damascus steel (e.g. iron and steel) there is the theoretical problem that the cutting edge could wear out in a “saw-like manner” because the soft layers in the compound wear out much faster than the hard ones. However, since the carbon content in thin layers quickly balances out through diffusion, this is usually not a problem in practice if the layers are not too thick.
Damascus steel in various cultural areas
Damascus steel in Southeast Asia
Damascus steel was also produced in Indonesia . This was mainly used for the so-called keris (a dagger with a pointed, often wavy blade). These Indonesian steels often have an increased nickel content , which indicates that this steel was made with iron meteorites . These often have a high proportion of this element. According to the mythology of the Empu (Indonesian master blacksmith), iron came from heaven and was sent by the gods.
The melted Damascus steel "Wootz" or "Bulat"
origin
Melted Damascus steel is known as Wootz steel, or “Wootz” or “Bulat” for short. The term " Wootz " comes from the Indian language area. The steel was probably manufactured for the first time in Central Asia, and later in the whole of the Oriental-Arab region .
Performance and quality
Oriental Damascus steel is often referred to as legendary and far superior to medieval European sword steels. These statements do not correspond to reality. There were great differences in quality between the oriental steels. However, there are swords of excellent quality that have a very good edge retention and break resistance and also have a high artistic value.
What can be said for sure is that the carbon content of the blades made from Wootz is considerably higher than that of most sweat damask swords. Most of the documented finds of Wootz products have carbon contents between 1.2 and 1.8% in common. This high carbon content is necessary because the formation of the pattern is only represented by the distribution of carbon in the form of carbides and their appearance in the steel.
From a metallurgical point of view, such materials are considered to be over pearlitic or almost ledeburitic . This means that the carbon can only be dissolved in the iron to a limited extent or not at all during the heat treatment. It is in the form of precipitations of cementite (carbide). These precipitates and the form of their appearance largely determine the pattern that is highlighted in the steel by polishing and etching. This is precisely why these alloys are quite brittle, especially after heat treatment. This led to z. B. Swords were only slightly remunerated in places, otherwise they would have broken quickly.
Manufacture of Wootz
The starting material, the so-called Wootz cake, consists of iron , around 1.5% carbon and tiny traces of impurities, e.g. B. vanadium , molybdenum , chromium , niobium or manganese . The material is melted and then slowly cooled. Dendritic austenite crystals are formed in the process . They have an elongated, fir tree-like shape and push themselves further and further into the melt. The impurities do not fit into the crystal lattice and are pushed into the gaps.
If the material continues to cool and falls below the austenite lower limit temperature, randomly distributed cementite particles are formed . When the steel is forged, the cementite particles dissolve again, except in the boundary area between the austenite crystals where the foreign matter has accumulated. The steel is now each time heated up to the temperature range in which new cementite particles are formed. Then the steel is forged . This is how the cement parts are gradually created. To make them visible, the surface still has to be polished and etched.
With swords and sabers made of this steel, like welding damascus steel, a pattern is created on the blade by polishing or etching. Such weapons were manufactured until around the end of the 18th century. The production of this steel has since been almost forgotten because the properties of such a special metallurgical structure do not reflect the requirements of a modern and high-performance material. Due to the increasing purity and reproducibility of mono steels, Damascus steel has been reduced to its decorative properties in recent times. Some enthusiasts and specialists are of the opinion that the fire-welded composite steel blade is the more noble and technically better variant. Indeed, these handcrafted masterpieces are beautiful unique pieces and show a "living" steel.
There are now a number of experts who have mastered this old manufacturing process.
research
In 2006, electron microscopic examinations at the Technical University of Dresden found carbon nanotubes up to 50 nm in length and 10 to 20 nm in diameter made of carbon atoms in a Damascus sword from the 17th century , which indicate a still unknown metallurgical process. There is speculation that, for example, wood or leaves were added to the melt using special Indian iron ores as catalysts or crystal formers. However, there is still no evidence that these nanoparticles have any effect on the technical properties of the steel. An assumed increased corrosion resistance could not be proven.
In this steel, according to the researchers, it is martensite particles arranged in a wave shape in the structure that are supposed to determine the supposedly excellent properties. That is already in the refining reached the iron and not by the United forge several types of steel. We cannot speak of Damascus forging technology here. This crude steel, manufactured using the crucible melting process, is known as Wootz .
The way in which Wootz Damascus steel was used in the Middle Ages and modern approaches to steel blades present a sober picture. The above-mentioned investigations do not lead to any particular improvements in properties compared to normal steel or welded damascus steel.
Damascus steel and the samurai sword
As noted above, samurai swords are not actually made of Damascus steel, but of refined steel (also a welded composite steel ). Often used different blade structures with, for example, tougher steel in the core or on the back as well as the differential hardening of the blade have only the basic process of processing with Damascus steel in common.
The steel used to make a Japanese sword is folded and welded back onto itself (refining). The reason for this is the achievement of a certain homogeneity (even distribution of the chemical components in the steel) and the removal of slag , which is essential because of the impure raw material Tamahagane . Tamahagane is obtained in the so-called Tatara and corresponds to the European lob as a racing kiln product. The Tatara corresponds to a very large racing oven. Tamahagane is a commodity and is no longer made by the Japanese blacksmith himself. However, the refining is done by the blacksmith, who forges suitable pieces of Tamahagane in advance and combines them in a block. The blacksmith therefore has no refined steel available as a commodity. For samurai swords, refining is part of the process of making the product. A combination of different starting materials takes place, due to the high number of folds it is a homogenization, i.e. a refining, not the production of a Damascus steel.
The optical properties of refining steel, known as Hada in Japanese , are one of the most important quality features of Japanese blades. In addition, the focus is on optical effects through structures that essentially result from heat treatment. These martensite structures occur in the hardness zone, the hamon , and are classified according to size (Nie, Nioi) and appearance (e.g. Kinsuji, Chikei, Inazuma, Sunagashi or Utsuri). They are also part of the quality characteristics of a Japanese blade and determine its value significantly.
Use in firearms
Barrels of firearms have always been made of Damascus steel ( fire-welded composite) . The material offers exactly the properties that are required for firearms: it is flexible, tough and strong. Early cast barrels (found in hand rifles , hook rifles and wall rifles, among others ) were heavier and could burst due to the pressure when firing , which was associated with a considerable danger for the shooter . Damascus barrels had a higher strength despite the lower weight, but the multiple welding processes also brought an increased risk of bursting when fired.
Damascus barrels were made by winding individual steel wires around a rod and forging them together. In Suhl Weapons Museum is a fine example to see where a band of several twisted Damascus steel strands was forged around a pole in a run.
There are improved methods in which the Damascus ribbon was wound onto a pipe and welded.
Damascene
Damascus denotes an etching process on a polished metal surface, which is intended to simulate the pattern of Damascus steel. It is not Damascus steel. Such effects can sometimes not be visually differentiated from real Damascus steel. In heraldry , damascene is understood to be the decoration of coats of arms with plant-like flourishes and tendril patterns in the style of arabesques .
Damascus steel today
use
Nowadays, due to the aesthetic appeal of the etched surface, Damascus steel is enjoying increasing popularity again, especially for the manufacture of kitchen and hunting knives . Utensils and jewelry are also made from it. Almost always the usefulness of using Damascus steel is limited to its decorative value. Some kitchen knives get their edge retention through the use of a high-strength steel core. Damascus steel only forms the outer decorative layers and must be softer than the core to minimize the risk of breakage. A monosteel fulfills this task in the same way. With hunting knives, the use of Damascus steel ensures good flexibility and increased resistance to breakage. In practice, only a few steels meet this requirement, which is not clearly defined. The term "Damascus steel" has only been used again in the USA since 1973.
Damasteel
So-called Damasteel can be produced using newer manufacturing processes. This is a completely different process in which rust- resistant types of steel in powder form are mixed together in such a way that a pattern is created. Due to high pressure and high temperatures at the same time, the material sinters into a dense steel block, which is cut open and further processed. After production, this steel is called powder metallurgical steel.
The process was only developed in 1993. The reason for the development was that steels alloyed with chromium cannot be hot-welded. Stainless steel is a high-alloy steel that must contain more than 13% chromium in the matrix in order to be rust-resistant. Due to the carbon content, these steels are never completely rustproof.
Damascus steel exotic
In addition to the conventional Damascus steel in rusting and rustproof versions, there are so-called "Damascus exotics", which are characterized by the special origin of one or two types of steel. Collectors and enthusiasts are interested, but the properties do not go beyond those of other suitable industrial steels.
The exotics include:
- Leo-I-Damascus - 320 layers (gun barrel steel from Leopard-I tank with tool steel)
- Leo-II-Damascus - 320 layers (cannon barrel steel from Leopard-I tanks with roller bearing steel)
- Leo III Damascus - 320 layers (cannon barrel steel from Leopard I tanks with tool steel and roller bearing steel)
- Leo-IV-Damascus - 640 layers (gun barrel steel from Leopard-I tanks with tool steel, roller bearing steel and cold work steel)
- Eurofighter damask - 320 layers (on-board cannon material from the " Eurofighter " fighter jet with tool steel)
- Tirpitz Damascus - 320 layers ( Tirpitz material with tool steel)
- G3 Damascus (barrel material from the G3 assault rifle with a tool steel)
- Iron meteorite damask
See also
literature
- Manfred Sachse : Damascus steel. Myth. History. Technology. Application. Stahleisen-Verlag, 1993, ISBN 3-514-00520-6 .
- Heinz Denig: Old blacksmithing. Volume 2: Damascus steel. 2nd Edition. Self-published, 2000, ISBN 3-87022-258-1 .
- Manouchehr M. Khorasani: Arms and Armor from Iran - The Bronze Age to the End of the Qajar Period. Legat, Tübingen 2006, ISBN 3-932942-22-1 . (including ancient weapons science)
- Masakuni Ishii, Minoru Sasaki: Kodaitô to Tetsu no Kagaku (Swords of the Early Period and the Chemistry of Steel). Tokyo 1995, ISBN 4-639-01300-0 .
- L. Kapp, H. Kapp, Y. Yoshihara: The Craft of the Japanese Sword. Tokyo / New York 1987, ISBN 4-7700-1298-5 .
- German: Japanese swordsmithing. Ordonnanz-Verlag, Freiburg i.Br. 1996, ISBN 3-931425-01-0 .
- Roman Landes: Knife Blades and Steel: Technological Consideration of Knife Edges. 2nd Edition. Wieland-Verlag , Bad Aibling 2006, ISBN 978-3-938711-04-0 .
- Stefan Mäder : Steels, stones and snakes. Humboldt University, Berlin 2001, DNB 971697175 .
Web links
- Damascus knives for self-forging. On: die-roemer-online.de
- Difficulty and sorcery. The "historical core" of the magic swords. University of Kiel
- The Key Role of Impurities in Ancient Damascus Steel Blades (English)
- Crusade against nanotechnology. On: Wissenschaft de of November 16, 2006
Individual evidence
- ↑ polyme.ch
- ↑ An example from a German auction house. ( Memento from December 8, 2015 in the Internet Archive )
- ^ Regionalgeschichte.net
- ↑ Eat Hammer Anvil. In: Archeology Online
- ↑ The Celtic rapiers
- ↑ Materials and process engineering section ( Memento from November 4, 2013 in the Internet Archive ) (PDF; 1.0 MB)
- ↑ Secrets of European swordsmithing revealed. In: welt.de
- ↑ archaeologie-online.de
- ^ M. Reibold, P. Paufler, AA Levin, W. Kochmann, N. Pätzke, DC Meyer: Materials: Carbon nanotubes in an ancient Damascus saber. In: Nature. 444, (2006), p. 286. (English)
- ↑ scotts_talisman_damaskalat_und_nanodraht. In: Archeology Online
- ↑ home.datacomm.ch
- ↑ https://www.washingtonpost.com/wp-dyn/content/article/2006/02/14/AR2006021402058.html