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Yasugi Specialty Steel and Tatara

Unpaku Steel Limited, Co.

Many types of industries prospered during the Meiji Period, and demand for steel grew rapidly. Cheap European steel was imported to meet this need, while the tatara business, unable to shift to mass production, found itself at a crossroads. In response to this situation, five individuals who managed tatara in Okuizumo and Hoki established the Unpaku Steel Limited Partnership Company in a wholesalers' district near Yasugi Harbor, and began to manufacture and sell tatara products. (The name “Unpaku” comes from combining alternate readings of the Chinese characters for mo and ho, used in the names of the regions from which the partners came.) This marks the origin of the present-day Hitachi Metals Yasugi Works.

Unpaku Steel installed a steam hammer in 1902, completed a crucible furnace in 1912, and began manufacturing steel for edged tools using iron and kera as the basic ingredient. The company in 1913 successfully manufactured high-speed tool steel using crucible steel. Around that same time the company also embarked on research into manufacturing alloy steel through melting in an electric furnace, and began to recover iron from tatara iron slag using a sinter smelting process developed by Fuyukichi Obana, an engineer working at the Hiroshima National Mine. In 1915, Unpaku Steel installed a Stassano-type electric furnace, and the following year the company successfully manufactured high-speed tool steel using an electric furnace, the first time this was accomplished in Japan. Supported in part by the economic boom stimulated by the outbreak of World War I, the company next increased its industrial plant by building new or additional electric furnaces, hammers, rolling machines, cylindrical blast furnaces for use with wrought iron, and open-hearth furnaces, in the process steadily solidifying its position as a steel manufacturer. Unpaku Steel built an Obana-style small blast furnace (a square charcoal pig iron furnace) in 1918, and began to manufacture charcoal pig iron using akome iron sand as the iron source. This had provided a stable supply of iron sand-based primary source iron.

Torigami Charcoal Pig Iron Factory
Torigami Charcoal Pig Iron Factory

This square furnace stayed in use until 1965. It was designated an Industrial Heritage Site by the Japan Industrial Archeology Society in 1996, and in 1997 was registered as a Tangible Cultural Property (Architectural) by the Cultural Affairs Council at the Ministry of Education.

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