Katana are considered to be the world’s strongest cutting swords. They have a functionally gradated structure that allows the hard and tough outer metals (mune) to wrap around the softer and more flexible core metal (ha). The resulting blade is both exceptionally sharp and strong, able to resist breakage even under extreme stress.
The katana is also unique in that it can be used as either a slashing or thrusting weapon, due to its distinctive curved shape. This makes it perfect for the slashing attacks of mounted warfare and the thrusting moves required of on-foot combat.
To make a katana, swordsmiths use specialized Japanese steel known as tamahagane. It is created from traditional smelting methods by heating iron sand and charcoal in a clay tatara furnace, creating layers of varying carbon content. The high-carbon steel forms the katana’s hard, razor-sharp edge, while the lower-carbon steel provides the sword’s toughness and shock absorbency.
After the smith removes all slag from the tamahagane, he heats the harder high-carbon steel and hammers it into a long channel that fits around the softer low-carbon steel. Then he welds the two pieces together, forming a single bar of steel that can be forged into a katana. The fusion of the different steels creates the distinct wavy line, or hamon, that is one of the most distinguishing traits of the katana. buy a katana here