What is Damascus Steel?
Do you know about the origins of Damascus steel?
It’s possible you have heard of Damascus steel, particularly if you are familiar with old swords, knives and guns. A book, The Art and Beauty of Damascus Steel, has been written on the subject. While this treatment of the topic might not do the book justice, Damascus steel is quite beautiful and holds much mystery.
Although the heyday of Damascus steel was between 900 and 1600 AD, the origins began as early as 300 BC in India. At that time, wootz steel was made using a new technique that produced high-carbon steel of unusually high purity. Glass was added to a mixture of iron and charcoal in a small, sealed, clay crucible, and it was then heated. The glass acted as a flux to combine with other impurities in the melt, allowing them to float to the surface. The result was a more pure steel. This technique spread from India to modern-day Turkmenistan and Uzbekistan around 900 and to the Middle East around 1000.
Modern metallurgical analysis has proven that Damascus steel differs from pattern welding (to be discussed later). Blacksmiths of today use pattern-welding techniques to reproduce the look of Damascus steel.
No one really knows why this steel is so unique, but it is believed to be due in part to its vanadium content. In addition, it is believed that the steel was “hot short” due to its sulfur and phosphorus content. Our theory would be that this hot shortness required a lower and more precise forging temperature than conventional European blacksmiths were accustomed to. The vanadium content, and possibly also molybdenum, could create “primary” carbides, which would not be affected by the lower-temperature thermal processing (forging). Some of the iron carbides might go into solution during forging, but the primary, vanadium carbides and certain other metallic carbides would flow in a pattern established by the forging process. These flow lines would lie parallel to the forging plane of the blade, and the bladesmith exploited this to create a more exotic pattern upon polishing and etching of the blade.
Another forging-process creation was not known until recent metallurgical analysis revealed the presence of carbon nanotubes and nanowires in a 17th-century sword. The complex forging and annealing process is believed to have developed the nano-scale structures. These nanostructures help give Damascus steel its distinctive properties.
The origin of the Damascus steel name is almost as mysterious as the steel itself. The assumption is that the steel or the swords were made in Damascus, Syria. It’s just as likely, however, that it comes from the Arabic word “damas” meaning water, referring to the surface pattern that resembles turbulent water. One source refers to swords made by a man named Damasqui, which could also have been the origin of the name.
Damascus steel is both hard and flexible, which made it an ideal sword-making material. The primary and/or precipitated carbides that create the pattern are much harder than the low-carbon steel matrix. These carbides allowed the swordsmith to make an edge – using the precipitated carbides – that would cut hard materials, and the softer matrix allowed the sword to remain tough and flexible.
The beauty of Damascus steel has resulted in craftsmen attempting to duplicate it. Present-day blacksmiths use one of two techniques: cable Damascus or pattern welding. The cable technique began with the availability of steel-wire rope in the 1830s. The wire rope is forged, creating repeating images along the blade similar to the Damascus steel of old.
Pattern welding involves welding different types of steel and iron bars together to form a billet. The billet is drawn out and folded several times during the forging process. Historically, Japanese samurai swords were made with this technique. Typically, the folding and re-forging process is repeated from eight to 16 times, which helps refine the impurities and remove excess carbon. Believe it or not, if you start with a single bar and fold it 16 times, you will end up with 65,536 layers. If, however, you start with a pattern-welded, eight-layer billet, 17 folds will result in 1,048,576 layers! The resulting layers will be aligned parallel to the forging direction, producing superior strength properties as well as a pattern similar to the Damascus patterns of old.
In spite of the many mysteries about Damascus steel, now you know what it is and how today’s craftsmen duplicate its unique properties and beauty. IH
This article is featured in Industrial Heating's Top-10 Heat-Treated Holiday Gifts. Click on the present to find more gift ideas and to learn how these gifts benefit from thermal processing.