the eighth century, the shaft type furnace (Fig. 1b) appeared in eastern Japan. However, in western Japan, the box type In traditional Japanese smelting and forging, three furnace underwent a number of improvements in both the characteristic technologies can be identified that bellows and the underground structure. During the sevenmay provide a basis for a new process concept in teenth century, the box type furnace developed into the the production of iron and steel. First, ironsand, the Tatara furnace, shown in Fig. 1c. The wall of the furnace use of which is problematic in modern ironmaking, was about 1·3Ö 3 m in section and about 1·3 m in height, was used instead of ironstone. The titanium oxide and made of soil. The slag notches were made along the present was effective for keeping the slag fluid and short sides, while the tuyeres were placed on the long sides. increasing the carbon content of the product, Using this process, approximately 10 4 t of iron and steel thereby decreasing the activity coefficient of FeO in were produced each year in Japan during the eighteenth the slag. Second, two types of operation were and nineteenth centuries. carried out with almost the same type of furnace. InTraditionally, ironstone (magnetite) was used as a raw one of the operations, mainly molten pig iron was material for the smelting process in Japan. However, ironproduced and, in the other, steel bloom (>50 wt-% sand was eventually adopted in its place. Because ironsand of total product) and molten pig iron. The main contains titanium oxide, it is considered unsuitable for use controlling factors were the type of raw material in modern ironmaking. The rst question to be addressed (titanium content of ironsand) and the oxidising in this paper will be the reason why ironsand was used potential in the furnace, which influenced the instead of ironstone in traditional Japanese smelting. degree of carburisation and decarburisation of theIn the seventeenth century, the technology for producing iron. Third, it is thought that traditional Japanese molten pig iron by using the Tatara process was established. steel is the best material for Japanese swordmaking.At that time, pig iron was converted to middle or low This was confirmed by an experiment with different carbon bloom by using a special blacksmithing technique materials. In the case of traditional Japanese steel, called Ohkaji. This can be called the traditional Japanese both the homogeneity of the carbon distribution indirect ironmaking system. 2 However, from the beginning and the inclusion content in the original material can be improved by the forging process, since the degree of contamination during forging is less. With modern steel, weldability in forging is adversely affected by contamination during forging. This means that the complex combination of material and total process is important for producing the particular product.
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