How Damascus and Bulat Steel Are Made: History, Structure, and Forging

For many centuries there was the mystery of Damascus steel. Only in 1841 did the Russian scientist and metallurgist P.P. Anosov propose methods for making Damascus steel.

How does carbon affect the properties of steel?

Steel is an alloy of iron and carbon, and the carbon content in steel can reach up to 2%. If it is higher than that, the material is already cast iron. The properties of steel depend heavily on the concentration of carbon it contains. When carbon is scarce (less than 0.1–0.2%), the steel turns out soft, plastic, and ductile, yet its strength and hardness are low.

A sword made from such soft steel will bend and stay bent, and a blade forged from it will go dull after the very first blow. When there is a lot of carbon (1–2%), the steel — after appropriate heat treatment — becomes very strong, hard, and springy, but at the same time it also gains brittleness. A sword made from this steel cannot be bent into a half-circle without snapping, and it cannot be sharpened to a keen edge because the blade will chip.

Only when both grades are bound together, closely interwoven at the microscopic level and harmoniously complementing each other, do you get Damascus steel — the steel that possesses the qualities that earned it its well-deserved fame.

Damascus steel is a composite

The secret of Damascus steel therefore lies in its composite structure. The ancient masters knew nothing of this; they had to feel their way forward, selecting the components for smelting Damascus steel through years of trial and error and testing different methods of working it. They resorted to additives of herbs, flowers, and various potions — every master had his own proportions, his own methods of forging and quenching. But the secrets of the ancient masters are lost forever.

This became clear thanks to the painstaking research of both known and unknown scientists. Just as a mountain summit can be reached from the south, north, west, or east, Damascus steel can be made by different methods. The main thing is to achieve the required result.

Ancient methods of making Damascus steel

There were various methods of making Damascus steel, and here we describe two that, presumably, could well have been used by ancient craftsmen. Into the forge (a clay furnace) of an ancient Egyptian or Indian metallurgist, small pieces of iron ore and charcoal were loaded; the charcoal was ignited, and bellows fed air into the forge, which helped raise the temperature.

The carbon monoxide formed as the charcoal burned reduced the ore to pure iron. The reduced pieces partially sintered together, forming a porous iron briquette. The surface of these pieces, interacting with carbon, became saturated with it, while the core remained uncarburized. The melting point of steel falls as its carbon content rises.

The temperature in the forge was high enough to melt the surface, heavily carburized parts of the former ore pieces, but not high enough to melt their core — almost pure iron. The molten regions, fusing together, formed a continuous steel base (a matrix) inside which sat inclusions of pure iron.

As it cooled, the molten high-carbon steel crystallized as tree-like crystals, and within their branches — like cones on fir trees — the unmelted particles of low-carbon steel became trapped. Then came repeated forging, which had to be done so that the tree-like crystals were not destroyed but only crumpled.

In this process the particles of soft steel were stretched out, took on a fibrous form, and interwove with the crystals of high-carbon steel, forming the wavy pattern characteristic of Damascus steel. From the forged strips, craftsmen made blades, swords, daggers, spearheads, armor, and other items so essential to the ancient warrior. Next came quenching — heating the steel to a certain temperature and cooling it rapidly.

In this way the high-carbon steel became strong and hard, the low-carbon steel stayed tough and soft, and the composite of these steels acquired the properties of Damascus steel.

The technology for making samurai swords

The technology for making samurai swords (katana) had its own particularities. For them, ores were used that, besides iron, contained a number of alloying elements — nickel, molybdenum, and others. The properties of steel are worsened by the presence of sulfur and phosphorus — harmful impurities that are distributed unevenly through the volume of the ingot.

To get rid of them, the iron obtained after reducing the ore in the forge was forged into sheets or rods and buried in the ground in marshy terrain. There it lay for several years, being periodically dug up and inspected for its appearance.

Such porous metal was carburized, so that high-carbon steel formed on its surface and near the holes, while pure iron remained inside. This "piece of cheese" was folded in two and subjected to hot forging until the folded parts fully bonded together. Then the resulting sheet was folded in two again and forged once more.

This process was repeated many times, producing a monolithic metal consisting of several thousand — or even tens of thousands — of the thinnest alternating layers of hard and soft steel. From such forgings, Japanese smiths made their famous samurai swords and knives. In this way the principles of making Damascus steel were unraveled.

And if you approach the question scientifically, you can say that there are no fundamental secrets in the technology of producing Damascus steel. It is clear what it was made from, how it was forged and quenched, how it was ground and polished. But a Damascus blade, saber, or sword is not only the product of a particular technology. It is also a work of art. Into every ancient blade, besides the master's skill, art and inspiration were invested.

And these things are unrepeatable. Each ancient blade was made not in hours but over years. The master often brought it to a mirror shine with the fingers of his own hand, day after day, month after month. And from that shine a mysterious chill appeared in the metal, seeping into the soul of the person who touched the blade — a feeling of the incomprehensible arose, as always happens on contact with a true work of art.

The secrets of this art have not yet been unraveled. But true art must have a mystery. And perhaps it is not worth unraveling the ancient mystery of making Damascus steel, so that the art itself does not vanish.