Tamahagane Steel: The Secret Behind Samurai Swords

Posted by lisa1988ann on July 13th, 2013

Japanese sword making process is considered one of the most labor-intensive smithy works in the world. Many traditional bladed weapons such as katana, tachi and kodachi are made using this method. Some of the weapons such as the katana have legendary connotations associated with them. In feudal Japan, katana was known as the "samurai sword", and carried great respect for itself and its wielder. You might be wondering, "What makes a katana different from any other sword? What makes is so special?"

Apart from the traditional process involved in making a katana, there is one factor which differentiates it from the rest of the swords: Tamahagane steel. The steel alloy used to make a katana is made from a traditional Japanese smelting process, which results in various layers of steels with different carbon concentrations. The resulting steel is free from impurities and has an even content of carbon throughout.

Tamahagane is a very high quality steel and usually costs almost 50 times more than normal steel. The word tama means "round and precious" in Japanese language, while the word hagane means "steel". Considering its price, the meaning of a "round and precious steel" is pretty apt for it. The carbon percentage is usually 1% in Tamahagane steel and never crosses more than 1.5%. 

Like all steels, Tamahagane is an alloy made of iron; particularly two main types of iron sands: acome and masa. Acome is low-quality iron sand, whereas masa is of higher-quality. The proportion in which these two sands are mixed is what gives sword making katana process its unique characteristics.

The process begins by putting a part of the iron sand mixture in a clay furnace. The furnace is 4 feet tall and measures around 12 feet by 4 feet in dimensions. After the furnace is completely dried, it is heated to a temperature of about 1000 ºC. Charcoal is then added into the furnace to make the alloy; that is what gives Tamahagane its hardness.

Additional iron sand mixture is added every 10 minutes and the contents in the furnace are frequently turned over to aid in mixing. The complete process takes around 2 to 3 days to complete depending on the number of people working and the amount of metal required.

After the process is complete and the steel has solidified, the clay furnace is destroyed by breaking it; only Tamahagane steel remains now. The most excellent steel is where the oxidation process is the strongest; that is around the edges of the metal block. If the steel is bright silver in colour, it is considered good enough to make blades and swords with it.

The steel thus obtained is high in carbon content; it is between 1% and 1.5%. This makes it very desirable for sword making as it is very tough and durable. The strength and permanence of weapons made from Tamahagane steel are legendary even to this day. 

Although many modern steels have far surpassed Tamahagane in popular usage, it is still fascinating to heed that the process was conceived by smiths who lived a long time ago in feudal Japan where no high quality iron ore was available.

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