Dr. Çetiner’s Blogs (Dr. Beytullah Gültekin Çetiner)

Damascus Steel

Damascus steel is a steel used in Middle Eastern swordmaking from about 1100 to 1700 AD. Damascus swords were of legendary sharpness and strength, and were apocryphally claimed to be able to cut through more “ordinary” European swords and even rock. The technique for making Damascus steel remains a mystery even with the presences of numerous well-preserved examples. Recent research into the structure and composition of the steel by a Dresden scientist claims that the strength of the steel was a result of carbon nanotubes and carbide nanowires present in the structure of the forged metal.

Damascus swords often had an obvious patterned texture on their surface. Several other steelmaking techniques also result in patterned surfaces, and have often been sold as Damascus steel, Damascened steel and sometimes watered steel. The most common technique for producing these materials is the pattern welding, which is today widely used for custom knife making. Skilled swordsmiths can manipulate the patterns to mimic the complex designs found in the surface of the original, medieval Damascus steel.

Another theory behind the hardness of Damascus steel is that the steel contains a small amount of vanadium, which would theoretically strengthen the blade.

Manufacture of Damascus Steel
The original Damascus steel swords may have been made in the vicinity of Damascus, Syria, in the period from 900 AD to as late as 1750 AD. Damascus steel is a type of steel alloy that is both hard and flexible, a combination that made it ideal for the building of swords. It is said that when Damascus-made swords were first encountered by Europeans during the Crusades it garnered an almost mythical reputation—a Damascus steel blade was said to be able to cut a piece of silk in half as it fell to the ground, as well as being able to chop through normal blades, or even rock, without losing its sharp edge. Recent metallurgical experiments, based on microscopic studies of preserved Damascus-steel blades, have claimed to reproduce a very similar steel via possible reconstructions of the historical process.

When forming a batch of steel, impurities are added to control the properties of the resulting alloy. In general, notably during the era of Damascus steel, one could produce an alloy that was hard and brittle at one extreme by adding up to 2% carbon, or soft and malleable at the other, with about 0.5% carbon. The problem for a swordsmith is that the best steel should be both hard and malleable — hard to hold an edge once sharpened, but malleable so it would not break when hitting other metal in combat. This was not possible with normal processes.

Metalsmiths in India and Sri Lanka perhaps as early as 300 BC developed a new technique known as wootz steel that produced a high-carbon steel of unusually high purity. Glass was added to a mixture of iron and charcoal and then heated. The glass would act as a flux and bind to other impurities in the mixture, allowing them to rise to the surface and leave a more pure steel when the mixture cooled. Thousands of steel making sites were found in Samanalawewa area in Sri Lanka that made high carbon steel (Juleff, 1996). These steel making furnaces were built facing western monsoon winds and wind turbulance and suction was used to create heat in the furnace. Steel making sites in Sri Lanka have been dated to 300 BC using carbon dating technology. The technique propagated very slowly through the world, reaching modern-day Turkmenistan and Uzbekistan around 900 AD, and then the Middle East around 1000 AD.

This process was further refined in the middle east, either using locally produced steels, or by re-working wootz purchased from India. The exact process remains unknown, but allowed carbides to precipitate out as micro particles arranged in sheets or bands within the body of a blade. The carbides are far harder than the surrounding low carbon steel, allowing the swordsmith to make an edge which would cut hard materials with the precipitated carbides, while the bands of softer steel allowed the sword as a whole to remain tough and flexible.

The banded carbide precipitates appear in the blade as a swirling pattern. By manipulating the ingot of steel in a certain way during forging, various intentional patterns could be induced in the steel. The most common of these was a pattern of lateral bands, often called ‘Mohammed’s Ladder’, most likely formed by cutting or forging notches into the surface of the ingot, then forging it into the blade shape (this is the method Pendray (below) used to reproduce the pattern). The notches resulted in different degrees of work hardening between top and bottom, and thus controlled the size of the carbide particles in the surface at those areas, and thus the appearance of the bands.

Reference: Wikipedia