Tamahagane

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Tamahagane (玉鋼:たまはがね, Tamahagane^?) is a type of Japanese steel. Translated as "jewel steel". It is mainly used to make Samurai swords, such as the katana, and some tools. Native supplies of the base iron ore are low, therefore they only smelt it for Japanese swordsmiths.

The smelting process used is different from the modern mass production of steel. A clay vessel about 1.1 meters (4 feet) tall, 3 meters (12 feet) long, and 1.1 meters (4 feet wide) is constructed. This is known as a tatara. After the clay tub has dried, it is fired until dry. A charcoal fire is started from soft pine charcoal. Then the smelter will wait for the fire to reach the correct temperature. At that point he will direct the addition of iron sand known as satetsu. This will be layered in with more charcoal and more iron sand over the next 72 hours. 4 or 5 people need to constantly work on this process. It takes about a week to build the tatara and complete the iron conversion to steel. When the process is done they will break the clay tub and take out the steel bloom known as a kera. At the end of the process the tatara will have consumed about 10 tons of satetsu and 12 tons of charcoal leaving about 2.5 tons of tamahagane.