“Damascus steel” whispered the merchant, pulling the sword out from under a pile of silks to show it to me. “The strongest, sharpest, and most durable steel in the world. All of you want it, only the most deserving can have it.”
I, the itinerant adventure arriving from the west, seeking my fortune here in the Middle East, had ventured into this bazaar in search of treasures not available back home. Like so many visitors before me who had crisscrossed this part of the world – the Crusaders, the Mamelukes, the Mongols, the Turks, the British – I was taken by both the beauty of the object, plus the power that such a weapon could bring.
“See the pattern, it looks like water, representing the river of paradise. This pattern also distributes the carbon in a way that gives the steel its near perfect qualities. It is manufactured using a secret process passed down through the centuries among a select few. You cannot get a weapon of this type anywhere else in the world.”
I had heard of Damascus steel, the steel that dominated the Middle Eastern weapons-making industry during the period between the 3rd and the 17th centuries. Reputedly (or maybe just “legendarily”) it had the strength to cut through steel armor, the delicacy to slice through a feather floating in midair, plus the durability to hold its sharpness longer than any other blade. And what else had I heard about Damascus steel? Oh yes, that it was an example of a great lost technology – since the decline and disappearance of the Damascus steel industry in the mid-18th century, the knowledge of how this steel was created and worked had been lost to the world. So how could there be a Damascus steel sword for sale in this Dubai bazaar in 1997?
“Wait a minute,” I told the bazaar merchant. “Nobody has known how to make Damascus steel for over 200 years. Where did you get this sword?”
The merchant shrugged his shoulders in resignation and replied “From a factory using a much more efficient method, it’s called mass production. Yes, the factory is in China. But for you, I’ll offer this beautiful sword at a special price.”
I looked at the sword – it was attractive, and certainly nothing I could readily find back home. And after all, he was offering a special price, just for me. So moments later I was leaving the bazaar with a genuine Damascus steel sword. I knew I would be the envy of all back home.
Later I got to thinking of the evolution that steel technology had gone through – the progression from Damascus steel, to crucible steel, through the Bessemer process, to the steels used in the today’s construction industry. And with that evolution, how the center of the steel industry had moved from India/Middle East, to Europe, to the United States, and now to China. So I guess it was not surprising that my steel sword had been made in China!
Steel is that specific mix of iron and carbon (plus a few other alloys) that gives it the optimal properties for the construction industry. Iron with a carbon content on the order of 0.05% makes wrought iron, tough and malleable, but nowhere near as strong as steel. Iron with a carbon content between 3 and 4% creates cast iron – very strong, but too brittle for many applications. In between, iron with a carbon content ranging from 0.2 to 1.5%, was Goldilocks-like (i.e., “just right”) – and made steel, a material that is strong, tough, and ductile. The problem with steel was that for thousands of years humans could not find a technology that could reliably and economically produce quality steel in quantity.
Thus it was that Damascus steel stood out in a world full of wrought iron. Damascus steel was based on wootz steel, a type of steel developed in South India and Sri Lanka thousands of years ago. The wootz steel ingots were exported to the Middle East where arms makers forged, folded, hammered, and otherwise worked the steel to spread the carbon content uniformly. The result was the mottled pattern of the surface, but also a material with superplasticity and impressive hardness. (Although some say that the secret was in the quenching – Damascus steel swords were said to be “quenched in blood”— with red hot swords thrust through the bodies of muscular slaves as the finishing touch of the production process.)
Today the secret behind Damascus steel is just beginning to be rediscovered. Recent forensic examinations have found that Damascus steel has a high content of beneficial alloys and carbon nanotubes – thanks to the Southern Indian ore, and the plant fibers used during the heating process, respectively.
With the decline in the importance of the sword as a battlefield weapon, the importance of Damascus steel waned, and the world sought steel appropriate for other uses. For example, as the proto-Industrial Revolution arose in Europe, a need developed for high quality steel for clock springs. In the 1740’s, Englishman Benjamin Huntsman discovered a process for making crucible steel. This involved first packing bars of wrought iron in powdered charcoal and heating it for several days; then repacking and reheating for several more days, until adequate carbon was absorbed and distributed throughout the metal. Next it was forged to further distribute the carbon, and then melted in a crucible and mixed with a flux that could remove unwanted slag particles. The resulting steel was high quality, but very expensive and could not be produced in large quantities.
With the rise of railroads the demand for steel increased significantly, since wrought iron rails had very little durability and severely limited the weight of the trains that could be carried. This required a much bigger scale production process, which was invented by Sir Henry Bessemer, who introduced his eponymous converter in 1856. The Bessemer converter was similar to a cast iron blast furnace but with holes in the bottom, through which air could be blown to bond with and remove carbon from the cast iron, reducing it to the carbon range of that of steel. During subsequent years various inventors offered improvements and alternatives (for example, the open-hearth method replaced Bessemer’s converter by 1900) to the design. Finally steel could be produced on a mass scale.
The United States became the biggest consumer and producer of steel. First it was used in railway construction, but with the availability of steel, more uses arose – especially in construction of the expanding American cities. The US steel industry came to dominate the world’s production, peaking at 85% of the world’s capacity in the years following World War II. Since then the industry has moved on to the next great growth economy, with China today producing more than half of the world’s steel.
In the US and elsewhere, the extensive industrial use of steel has led to a need for improvement and standardization of steel types. Spurred by the efforts of the Pennsylvania Railway, a precursor to the American Society for Testing and Materials (ASTM) was founded in 1898 for the specific purpose of defining material specifications.
Under the guidance of the ASTM, steel quality for structural use has improved though the years, with the standard for US structural steel evolving from ASTM A36 (36 ksi yield strength), through A572 (42 ksi yield strength), to today’s most prevalent, A992. A992 steel offers high strength (50 ksi yield strength) and good ductility (yield to ultimate strength ratio of 0.85) and weldability, making it ideal for structural applications.
A992 steel, and its production method, is a far cry from the Damascus steel of old. But it still dominates the world. When rolled into a wide flange or some other standard structural shape, it allows us to reach previously unheard of heights. So where did the idea for the wide flange come from? That is a story for next time!
So what ever became of my sword? It turned out it was too big to fit in my luggage, so I left it in Dubai in the safe keeping of my friend Amir, to be picked up on m next visit. However 7 trips later, I never did find a way to fit it in my luggage, so Amir is still watching over the sword that makes him (not me) the envy of all, even though it was made in China.
Building a sword, clock spring, or rail? You may want to use something else…but if you want to analyze structural steel, why not use CloudCalc, the scalable, collaborative, cloud-based engineering software. www.cloudcalc.com – Structural Analysis in the Cloud.
By Tom Van Laan
Copyright © CloudCalc, Inc. 2015
PS – I’d like to extend special congratulations to my daughter Katrina and all of her fellow members of the Brown University Class of 2015 upon their graduation this past weekend!