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Reading Selection, Lesson 18

The Samurai's Sword

Samurai holding a long sword

The Samurai's sword was a formidable weapon.

The properties of metal objects are determined not only by all the different metals that make them up but also by the way the metals are mixed together and treated. For thousands of years, metal workers, or smiths, have been altering the properties of metals by heating, hammering, and using other treatments to make objects as diverse as springs and gun barrels. The famous swords of the Samurai warriors of medieval Japan are one example of how smiths used the properties of particular metals for specific purposes.

The first Samurai were soldiers who were hired by landowners to protect their property from bands of robbers. From the 12th to the 19th century, even though Japan had emperors, the Samurai actually ruled Japan. The sons of Samurai were trained from early childhood for careers as warriors. A young man began his career at about age 15, when he received his first sword in a special ceremony.

Although each Samurai also carried a bow and arrow (and was trained in wrestling and judo), sword fighting was his most important skill. And the Samurai's swords were special indeed. Each Samurai had a long sword and a short one. The long sword, called the katana, was his main weapon. Its steel blade was designed to kill an enemy with one swipe!

To make a katana, a swordsmith used two types of steel. The core of the sword was made of soft, flexible, low-carbon steel (an alloy of iron with a little carbon). The jacket, or outer part of the sword, was made of hard steel that contained a greater proportion of carbon than did the core.The combination of these two kinds of steel gave the sword theflexibility to withstand a hard blow and a hard, razor sharp edge that would not be dulled during battle.

To make the blade, a piece of steel is repeatedly folded and hammered.

The swordsmith treated both steels with different techniques that improved the performance of the sword even further. He began by heating a lump of raw low-carbon steel—about the size of a brick—in a forge (a furnace that burns charcoal at very high temperatures).

The swordsmith then hammered the steel on an anvil until it was flat. Then he folded it in half crosswise and hammered it out again. He repeated this process many times to drive out any impurities from the metal.

Finally, he shaped it into a long, thin wedge. Next, the swordsmith began to work on the high-carbon steel. He followed the same process as the one he used for the low-carbon steel, but this time, he hammered and folded many more times. The final piece of metal had up to 30,000 folds or layers. The swordsmith made the jacket somewhat longer than the core.

Next, he joined together the two parts of the blade. The jacket was wrapped around the core, and the swordsmith heated and hammered the two pieces until they formed a solid bond. He had to be extremely careful; if an air bubble or piece of dirt remained between the two parts of the blade, the sword would be worthless in battle.

A swordsmith coats the sword with clay to control the cooling process.

The blade was then tempered, a process that is used to control the properties of the steel. The blade was heated and then cooled by being plunged into water. The swordsmith coated the sword with clay to control the cooling process. Where the coat of clay was thick, the steel would cool more slowly, and this would make it flexible. The edge of the blade was given a thin coat of clay, which allowed it to cool very quickly, a process that made the edge even harder.

The swordsmith sharpened and polished the blade. The layers, or grain, were visible on the shiny surface. Finally, he tested the blade—on iron sheets, armor, and, sometimes, the bodies of executed criminals.

The sword is cooled in water as part of the tempering process.

The Samurai swords were deadly but beautiful. The blades were decorated, and the handles were inlaid with pearls and other jewels.

Samurai swords were passed from generation to generation. Upon reaching manhood, a son received his father's sword, along with stories of the brave acts that had been accomplished with it.

Question

What techniques did the swordsmith use to modify the properties of different parts of a katana blade? Investigate how these techniques are applied for different purposes today.

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