The Katana swords are characterized by there properties: they are curved, light, single-blade, guard circular or square and the handle long enough to be held with both hands. These swords originated from Japan and were widely used by Samurai, japanese warriors.
An important method of getting the katana sword’s blade done is through forging. Steel from the blacksmith contains many impurities. Also it is homogeneous steel with different carbon content (a mixture of hardened steel and mild steel). To get the best formula, the Blacksmith treats the steel to get an optimal carbon content. It does this by heating the steel to 1300° C and hitting it with a hammer, bending and folding it, this way the steel is mixing and eliminating impurities.
Different ways of folding and tapping with a hammer produces a different texture in the final form of the blade. The final aspect is observed only after grinding the blade. Processing begins to forge a piece of 2.20 kg – 2.70 kg of steel. It is folded about six times, leading to a decrease of both surface and weight of the piece of steel. Six or more are required to obtain homogeneously folded steel.
These new steel blocks can be better homogenized by the blacksmith. Also distinctive layers appear on the final steel blade. The layers with more martensite offer a complex look to the blade. Finally the look of the blade is influenced by the heating process and the tempering of the blade.
Effects that can appear on the Katana swords are inazuma and kinsugi (shiny stripes of martensite embedded in the steel). Another effect is utsuri. It is a wavy and foggy area, whitish, which is located near the side edge and the steel is warming up in the immediate vicinity of the critical thermal point. This is a characteristic of Bizen tradition.
Katana swords are sometimes called “Damascus”. This appellation comes from swords created in the middle Ages by craftsmen and smiths in Damascus, used in battles against the crusaders. These swords were extremely strong and sharp. These were in particular recognized by the drawings in the steel. Currently it is not known precisely how these swords were produced. Although there are scientists who proclaim that had found the secret.
Damascus steel is a very rich mixture of carbon steel (1.5 – 2%) and a low carbon steel that are fused together in a crucible and forming together a block of steel suitable for forging. Working together the two types of steel (carbon rich and poor) makes the steel brittle pieces rich in carbon steel to distribute Saracen carbon, forming the so-called thick damask. Damascus steel gained prestige in front of the Europeans during battles with the Muslims, when they felt directly, in fighting quality.
However, Katana swords are superior weapons in terms of quality. The steel usage is more refined, smoother and tighter composition. Katana swords use lower carbon content than the swords of Damascus and thus less brittle. For a more detailed explanation on the making of katana be sure to check the linked site.