エチオピア西南部における伝統製鉄技術の冶金学的検証

抄録

  An abandoned traditional steelmaking in Southwest Ethiopia (Dime) has been restored, and the technology and knowledge used for the operation have been metallurgically analyzed. The restoration was carried out with local blacksmiths from September to October in 2004, and the steelmaking operation including mining, construction of a furnace and charcoal production, etc was successfully performed. Produced sponge iron contains 0.31∼0.48 mass% carbon without any impurities. The yield ratio of the iron was about 40%. The collected slag contains the elements of Fe, Si, Al, K, P, Ti and Mn, which are typical components of slag. The blacksmiths used three kinds of iron ore, named “Balt”, “Bullo” and “Gachi”. The former two ores mainly consist of goethite (α-FeO(OH)) and kaolinite (Al₂O₃•2SiO₂•2H₂O). The latter includes calcium phosphate hydrate (Ca₃(PO₄)₂•xH₂O) in its white part, as well as the goethite and kaolinite. The reason why the local blacksmiths specifically selected “Gachi” as the best ore for their steelmaking was discussed from the viewpoint of slag forming ability.