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Damascus steel - Wikipedia, the free encyclopedia

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Damascus Steel


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Close-up of a 18th century Iranian crucible forged Damascus steel sword
Damascus steel was a type of steel used in Middle Eastern swordmaking. Damascus steel was created from wootz steel, a steel developed in India around 300 BC, which was further refined by Middle Eastern Swordsmiths.[1] These swords are characterized by distinctive patterns of banding and mottling reminiscent of flowing water. Such blades were reputed to be not only tough and resistant to shattering, but capable of being honed to a sharp and resilient edge.[2]

The original method of producing Damascus steel is not known. Because of differences in raw materials and manufacturing techniques, modern attempts to duplicate the metal have not been entirely successful. Despite this, several individuals in modern times have claimed that they have rediscovered the methods in which the original Damascus steel was produced.[3][4]

The reputation and history of Damascus steel has given rise to many legends, such as the ability to cut through a rifle barrel or to cut a hair falling across the blade,[5] but no evidence exists to support such claims. A research team in Germany published a report in 2006 revealing nanowires and carbon nanotubes in a blade forged from Damascus steel.[6] This finding was covered by National Geographic[7] and the New York Times.[8] Although modern steel outperforms these swords, microscopic chemical reactions in the production process may have made the blades extraordinary for their time. Woody biomass and leaves are known to have been used to carbonize the Wootz ingots used in Damascus steel, and research now shows that carbon nanotubes can be derived from plant fibers,[9] suggesting how the nanotubes were formed in the steel. Some experts expect to discover such nanotubes in more relics as they are analyzed more closely.[1][7]

Contents

Etymology

Several theories on the origins of the term Damascus steel exist, but none of them may be confirmed definitively.[10] Damascus may refer to:

History


A bladesmith from Damascus, ca. 1900

Historians such as Hobson, Sinopoli, and Juleff state that the original damascus was produced from ingots of wootz steel, which originated in India and Sri Lanka[12] and later spread to Persia.[13] From the 3rd century to the 17th century, India was shipping steel ingots to the Middle East for use in Damascus steel.[14]

Loss of the technique

Production of these patterned swords gradually declined, ceasing by around 1750, and the process was lost to metalsmiths. Several modern theories have ventured to explain this decline, including the breakdown of trade routes to supply the needed metals, the lack of trace impurities in the metals, the possible loss of knowledge on the crafting techniques through secrecy and lack of transmission, or a combination of all the above.[3][4][15]

The original Damascus steel or wootz was imported from India to the Middle East.[3][4] Due to the distance of trade for this steel, a sufficiently lengthy disruption of the trade routes could have ended the production of Damascus steel and eventually led to the loss of the technique in India. As well, the need for key trace impurities of tungsten or vanadium within the materials needed for production of the steel may be absent if this material was acquired from different production regions or smelted from ores lacking these key trace elements.[3] The technique for controlled thermal cycling after the initial forging at a specific temperature could also have been lost, thereby preventing the final damask pattern in the steel from occurring.[3][4]
The discovery of carbon nanotubes in the Damascus steel's composition supports this hypothesis, since the precipitation of carbon nanotubes likely resulted from a specific process that may be difficult to replicate should the production technique or raw materials used be significantly altered.[15]

Reproduction

Bladesmith Tim Hancock forging a blade

Recreating Damascus steel is a subfield of experimental archaeology. Many have attempted to discover or reverse-engineer the process by which it was made.

Moran: billet welding

Close-up "modern damascus" (pattern welded) blades
Damascus Hand Made Axe - 256 Layers - 1095 Steel
Characteristic "organic" pattern of Damascus steel

Since the well-known technique of pattern welding produced surface patterns similar to those found on Damascus blades, some believe that Damascus blades were made using this technique. Pattern-welded steel has been referred to as "Damascus steel" since 1973 when Bladesmith William F. Moran unveiled his "Damascus knives" at the Knifemakers' Guild Show.[16][17] This "Modern Damascus" is made from several types of steel and iron slices welded together to form a billet.[18] The patterns vary depending on how the smith works the billet.[17] The billet is drawn out and folded until the desired number of layers are formed.[17] In order to attain a Master Smith rating with the American Bladesmith Society that Moran founded, the smith must forge a damascus blade with a minimum of 300 layers.[19]


Verhoeven and Pendray: crucible

J. D. Verhoeven and A. H. Pendray published an article on their attempts to reproduce the elemental, structural, and visual characteristics of Damascus steel.[3] They started with a cake of steel that matched the properties of the original wootz steel from India, which also matched a number of original Damascus swords to which Verhoeven and Pendray had access. The wootz was in a soft, annealed state, with a grain structure and beads of pure iron carbide which were the result of its hypereutectoid state. Verhoeven and Pendray had already determined that the grains on the surface of the steel were grains of iron carbide—their goal was to reproduce the iron carbide patterns they saw in the Damascus blades from the grains in the wootz.
Although such material could be worked at low temperatures to produce the striated Damascene pattern of intermixed ferrite and cementite bands in a manner identical to pattern-welded Damascus steel, any heat treatment sufficient to dissolve the carbides would permanently destroy the pattern. However, Verhoeven and Pendray discovered that in samples of true Damascus steel, the Damascene pattern could be recovered by aging at a moderate temperature. They found that certain carbide forming elements, one of which was vanadium, did not disperse until the steel reached higher temperatures than those needed to dissolve the carbides. Therefore, a high heat treatment could remove the visual evidence of patterning associated with carbides but did not remove the underlying patterning of the carbide forming elements; a subsequent lower-temperature heat treatment, at a temperature at which the carbides were again stable, could recover the structure by the binding of carbon by those elements.

Anosov, Wadsworth and Sherby: bulat

In Russia, chronicles record the use of a material known as bulat steel to make highly valued weapons, including swords, knives and axes. Tsar Michael of Russia reportedly had a bulat helmet made for him in 1621. The exact origin or the manufacturing process of bulat is unknown, but it was likely imported to Russia via Persia and Turkestan, and it was similar and possibly the same as damascus steel. Pavel Petrovich Anosov made several attempts to recreate the process in the mid-19th century. Wadsworth and Sherby also researched [4] the reproduction of Bulat steel and published their results in 1980.

Additional research

A team of researchers based at the Technical University of Dresden that used x-rays and electron microscopy to examine Damascus steel discovered the presence of cementite nanowires[20] and carbon nanotubes.[21] Peter Paufler, a member of the Dresden team, says that these nanostructures are a result of the forging process.[7][22]
Sanderson proposes that the process of forging and annealing accounts for the nano-scale structures.[22]

Damascus steel in gunmaking

Prior to the early 20th century, all shotgun barrels were forged by heating narrow strips of iron and steel and shaping them around a mandrel.[23][24] This process was referred to as "laminating" or "Damascus" and these barrels were found on shotguns that sold for $12.[23][24] These types of barrels earned a reputation for weakness and were never meant to be used with modern smokeless powder, or any kind of moderately powerful explosive.[24] Because of the resemblance to Damascus steel, higher-end barrels were made by Belgian and British gun makers.[23][24] These barrels are proof marked and meant to be used with light pressure loads.[23] Current gun manufacturers such as Caspian Arms make slide assemblies and small parts such as triggers and safeties for Colt M1911 pistols from powdered Swedish steel resulting in a swirling two-toned effect; these parts are often referred to as "Stainless Damascus".[25]

See also

Further reading

  • Eric M. Taleff, Bruce L. Bramfitt, Chol K. Syn, Donald R. Lesuer, Jeffrey Wadsworth, and Oleg D. Sherby, "Processing, structure, and properties of a rolled ultrahigh-carbon steel plate exhibiting a damask pattern," Materials Characterization 46 (1), 11–18 (2001).
  • J. D. Verhoeven, "A review of microsegregation induced banding phenomena in steels", J. Materials Engineering and Performance 9 (3), 286–296 (2000).
  • Jeffrey Wadsworth and Oleg D. Sherby, "Damascus Steels", Scientific American, pp. 94 – 99, February 1985.

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Spinning Carbon Nanotube

Carbon nanotubes (CNTs) are allotropes of carbon with a cylindrical nanostructure. Nanotubes have been constructed with length-to-diameter ratio of up to 132,000,000:1,[1] significantly larger than for any other material. These cylindrical carbon molecules have unusual properties, which are valuable for nanotechnology, electronics, optics and other fields of materials science and technology. In particular, owing to their extraordinary thermal conductivity and mechanical and electrical properties, carbon nanotubes find applications as additives to various structural materials. For instance, nanotubes form a tiny portion of the material(s) in some (primarily carbon fiber) baseball bats, golf clubs, or car parts.[2]
Nanotubes are members of the fullerene structural family. Their name is derived from their long, hollow structure with the walls formed by one-atom-thick sheets of carbon, called graphene. These sheets are rolled at specific and discrete ("chiral") angles, and the combination of the rolling angle and radius decides the nanotube properties; for example, whether the individual nanotube shell is a metal or semiconductor. Nanotubes are categorized as single-walled nanotubes (SWNTs) and multi-walled nanotubes (MWNTs). Individual nanotubes naturally align themselves into "ropes" held together by van der Waals forces, more specifically, pi-stacking.
Applied quantum chemistry, specifically, orbital hybridization best describes chemical bonding in nanotubes. The chemical bonding of nanotubes is composed entirely of sp2 bonds, similar to those of graphite. These bonds, which are stronger than the sp3 bonds found in alkanes and diamond, provide nanotubes with their unique strength.